Mesoscale and Nanoscale Physics
- [1] arXiv:2406.03529 [pdf, ps, html, other]
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Title: Ring states in topological materialsComments: 12 pages, 5 figures + 20 pages supplementary materialSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)
Ingap states are commonly observed in semiconductors and are often well characterized by a hydrogenic model within the effective mass approximation. However, when impurities are strong, they significantly perturb all momentum eigenstates, leading to deep-level bound states that reveal the global properties of the unperturbed band structure. In this work, we discover that the topology of band wavefunctions can impose zeros in the impurity-projected Green's function within topological gaps. These zeros can be interpreted as spectral attractors, defining the energy at which ingap states are pinned in the presence of infinitely strong local impurities. Their pinning energy is found by minimizing the level repulsion of band eigenstates onto the ingap state. We refer to these states as ring states, marked by a mixed band character and a node at the impurity site, guaranteeing their orthogonality to the bare impurity eigenstates and a weak energy dependence on the impurity strength. We show that the inability to construct symmetric and exponentially localized Wannier functions ensures topological protection of ring states. Linking ring states together, the edge or surface modes can be recovered for any topologically protected phase. Therefore, ring states can also be viewed as building blocks of boundary modes, offering a framework to understand bulk-boundary correspondence.
- [2] arXiv:2406.03624 [pdf, ps, html, other]
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Title: Entanglement harvesting in buckled honeycomb lattices by vacuum fluctuations in a microcavityComments: 10 pages, 6 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)
We study the entanglement harvesting between two identical buckled honeycomb lattices placed inside a planar microcavity. By applying time dependent perturbation theory, we obtain quantum correlations between both layers induced by the cavity field. Considering the vacuum state as the initial state of the cavity field and tracing out the time-evolved degrees of freedom, we analyze the entanglement formation using the concurrence measure. We show that the concurrence depends on the virtual photon exchanged and the positions of the layer through the interlayer photon propagator. Furthermore, we find that the formation of entanglement between equal energy electrons tends to be enhanced when they move in perpendicular directions. Our results indicate that a buckled honeycomb structure and a large spin-orbit interaction favor the entanglement harvesting.
- [3] arXiv:2406.03705 [pdf, ps, html, other]
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Title: Coherent control of a triangular exchange-only spin qubitEdwin Acuna, Joseph D. Broz, Kaushal Shyamsundar, Antonio B. Mei, Colin P. Feeney, Valerie Smetanka, Tiffany Davis, Kangmu Lee, Maxwell D. Choi, Brydon Boyd, June Suh, Wonill D. Ha, Cameron Jennings, Andrew S. Pan, Daniel S. Sanchez, Matthew D. Reed, Jason R. PettaSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)
We demonstrate coherent control of a three-electron exchange-only spin qubit with the quantum dots arranged in a close-packed triangular geometry. The device is tuned to confine one electron in each quantum dot, as evidenced by pairwise charge stability diagrams. Time-domain control of the exchange coupling is demonstrated and qubit performance is characterized using blind randomized benchmarking, with an average single-qubit gate fidelity F = 99.84%. The compact triangular device geometry can be readily scaled to larger two-dimensional quantum dot arrays with high connectivity.
- [4] arXiv:2406.03758 [pdf, ps, other]
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Title: Phonon heat conduction across slippery interfaces in twisted graphiteFuwei Yang, Wenjiang Zhou, Zhibin Zhang, Xuanyu Huang, Jingwen Zhang, Nianjie Liang, Wujuan Yan, Yuxi Wang, Mingchao Ding, Quanlin Guo, Yu Han, Te-Huan Liu, Kaihui Liu, Quanshui Zheng, Bai SongSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)
Interlayer rotation in van der Waals (vdW) materials offers great potential for manipulating phonon dynamics and heat flow in advanced electronics with ever higher compactness and power density. However, despite extensive theoretical efforts in recent years, experimental measurements remain scarce especially due to the critical challenges of preparing single-crystalline twisted interfaces and probing interfacial thermal transport with sufficient resolution. Here, we exploited the intrinsic twisted interfaces in highly oriented pyrolytic graphite (HOPG). By developing novel experimental schemes based on microfabricated mesas, we managed to achieve simultaneous mechanical characterizations and thermal measurements. In particular, we pushed the HOPG mesas with a microprobe to identify and rotate single-crystalline intrinsic interfaces owing to their slippery nature as is well known in structural superlubricity. Remarkably, we observed over 30-fold suppression of thermal conductance for the slippery interfaces by using epitaxial graphite as a control. Nonetheless, the interfacial conductance remains around 600 $\mathrm{MWm^{-2}K^{-1}}$ which surpasses the highest values for artificially stacked vdW structures by more than five times. Further, atomic simulations revealed the predominant role of the transverse acoustic phonons. Together, our findings highlight a general physical picture that directly correlates interfacial thermal transport with sliding resistance, and lay the foundation for twist-enabled thermal management which are particularly beneficial to twistronics and slidetronics.
- [5] arXiv:2406.03927 [pdf, ps, other]
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Title: Engineering open-shell extended edge states in chiral graphene nanoribbons on MgOAmelia Domínguez-Celorrio, Leonard Edens, Sofía Sanz, Manuel Vilas-Varela, Jose Martinez-Castro, Diego Peña, Véronique Langlais, Thomas Frederiksen, José I. Pascual, David SerrateSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)
Graphene nanostructures are a promising platform for engineering electronic states with tailored magnetic and quantum properties. Synthesis strategies on metallic substrates have made it possible to manufacture atomically precise nanographenes with controlled size, shape and edge geometry. In these nanographenes, finite spin magnetic moment can arise as a result of many-body interactions in molecular orbitals with $\pi$-conjugated character and subject to strong spatial confinement, for example at the zig-zag edges. However, owing to the mixing of the molecular orbitals and metallic states from the catalysing substrate, most of their expected quantum phenomenology is severely hindered. The use of in-situ ultra-thin decoupling layers can impede nanographene-metal hybridization and facilitate the expression of predicted properties. Here we show that the edges of narrow chiral graphene nanoribbons (GNRs) over MgO monolayers on Ag(001) can host integer charge and spin-1/2 frontier states. The electron occupation varies with the GNR length, which alternates even or odd number of electrons, thus resulting correspondingly in a non-magnetic closed-shell state or an open-shell paramagnetic system. For the latter, we found the spectral fingerprint of a narrow Coulomb correlation gap. Charged states, up to 19 additional electrons, were identified by comparing mean-field Hubbard (MFH) simulations of the density of states with experimental maps of the discretized molecular orbitals acquired with a scanning tunnelling microscope (STM). In consideration of the length-dependent magnetic moment and the discrete nature of the electronic structure, we envisage that GNRs supported by thin insulating films can be used as tailor-made active elements in quantum sensing and quantum information processing.
- [6] arXiv:2406.03941 [pdf, ps, html, other]
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Title: Magnetic Skyrmions: from lumps to supercompactonsComments: LaTeX: 27 pages, 7 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); High Energy Physics - Theory (hep-th)
The magnetic Skyrmion is described by one control parameter and one length scale. We study the two extreme limits of the control parameter -- infinitely large and vanishing - and find that the magnetic Skyrmion becomes a "restricted" magnetic Skyrmion and an O(3) sigma model lump, respectively. Depending on the potential under consideration, the restricted limit manifests differently. In the case of the Zeeman term, the restricted magnetic Skyrmion becomes a "supercompacton" that develops a discontinuity, whereas for the Zeeman term to the power 3/2 it becomes a normal compacton. Finally, we observe that the case of the Zeeman term squared, which can also be understood as a special combination of the Zeeman term and the easy-plane potential - realizable in the laboratory, the lump solution is an analytically exact solution for all values of the control parameter.
- [7] arXiv:2406.04007 [pdf, ps, html, other]
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Title: Modeling the spatial resolution of magnetic solitons in Magnetic Force Microscopy and the effect on their sizesI. Castro, A. Riveros, J. L. Palma, L. Abelmann, R. Tomasello, D. R. Rodrigues, A. Giordano, G. Finocchio, R. Gallardo, N. Vidal-SilvaComments: 18 pages. Supplementary Material is includedSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)
In this work, we explored theoretically the spatial resolution of magnetic solitons and the variations of their sizes when subjected to a Magnetic Force Microscopy (MFM) measurement. Next to tip-sample separation, we considered reversal in the magnetization direction of the tip, showing that the magnetic soliton size measurement can be strongly affected by the magnetization direction of the tip. In addition to previous studies that only consider thermal fluctuations, we developed a theoretical method to obtain the minimum observable length of a magnetic soliton and its length variation due to the influence of the MFM tip by minimizing the soliton's magnetic energy. Our model uses analytical and numerical calculations and prevents overestimating the characteristic length scales from MFM images. We compared our method with available data from MFM measurements of domain wall widths, and we performed micromagnetic simulations of a skyrmion-tip system, finding a good agreement for both attractive and repulsive domain wall profile signals and for the skyrmion diameter in the presence of the magnetic tip. Our results provide significant insights for a better interpretation of MFM measurements of different magnetic solitons and will be helpful in the design of potential reading devices based on magnetic solitons as information carriers.
- [8] arXiv:2406.04053 [pdf, ps, html, other]
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Title: Floquet Theory in an Irradiated Nodal Surface SemimetalComments: Initial draftSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Strongly Correlated Electrons (cond-mat.str-el)
A nodal surface semimetal (NSSM) features symmetry enforced band crossings along a surface within the three-dimensional (3D) Brillouin zone. The topological robustness of the same does not always come with nonzero Berry fluxes around nodal surfaces. Irrespective of that, however, light irradiation on such system can result in interesting dynamic behavior. We find that depending on the state of polarization, one can obtain additional Weyl points/ nodal surfaces in the Floquet Hamiltonian that the time periodic system gives rise to. For simplicity we only consider two band spinless models without any spin orbit coupling, the main emphasis being to understand the low energy behavior close to the band crossings and its evolution in a Floquet system in the high frequency limit. There we find the nodal surfaces to perish or get duplicated or triplicated for different polarization scenario or different NSSM Hamiltonians. One findings open up important directions on what out of equilibrium NSSM systems has to offer in many active fields including quantum computations.
- [9] arXiv:2406.04091 [pdf, ps, html, other]
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Title: Computing Floquet quasienergies in finite and extended systems: Role of electromagnetic and quantum-geometric gaugesComments: 15 pages, 6 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
We present an approach to compute the Floquet quasienergy spectrum of time-periodic systems. The method allows to characterize the light-matter interaction in finite and extended structures by carefully addressing the resolution of the position operator. In periodic systems we discuss the role of the quantum-geometric gauge freedom of Bloch states and employ a Wannier-based scheme to compute the required matrix elements. As a consequence, the method is accurate and applicable to a broad range of systems, from atoms and molecules to cold atomic gases and materials described by density functional theory, as well as model systems. We demonstrate the applicability of the approach by studying two cases: a particle trapped in a one-dimensional box and the semiconducting material BC$_2$N. We employ the first example to provide a numerical proof of the invariance of the Floquet quasienergy spectrum with respect to the choice of electromagnetic gauge. The analysis of BC$_2$N then serves to illustrate the physical effects described by the quasienergies, such as multiphoton resonances, and their expected range of occurrence in real materials in terms of external electric field and frequency of the drive pulse.
- [10] arXiv:2406.04097 [pdf, ps, html, other]
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Title: Resonant phonons: Localization in a structurally ordered crystalAlbert Beardo, Paul Desmarchelier, Chia-Nien Tsai, Prajit Rawte, Konstantinos Termentzidis, Mahmoud I. HusseinSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Phonon localization is a phenomenon that influences numerous material properties in condensed matter physics. Anderson localization brings rise to localized atomic-scale phonon interferences in disordered lattices with an influence limited to high-frequency phonons having wavelengths comparable to the size of a randomly perturbed unit cell. Here we theoretically reveal a new form of phonon localization induced by augmenting a crystalline material with intrinsic phonon nanoresonators with feature sizes that can be smaller or larger than the phonon wavelengths but must be relatively small compared to the phonon mean free paths. This mechanism is deterministic and takes place within numerous discrete narrow-frequency bands spread throughout the full spectrum with central frequencies controlled by design. For demonstration, we run molecular dynamics simulations of all-silicon nanopillared membranes at room temperature, and apply to the underlying thermalized environment narrowband wave packets as an excitation at precisely the frequencies where resonant hybridizations are evident in the anharmonic phonon band structure. Upon comparison to other frequency ranges where the nanostructure does not exhibit local resonances, significant intrinsic spatial phonon localization along the direction of transport is explicitly observed. Furthermore, the energy exchange with external sources is minimized at the resonant frequencies. We conclude by making a direct comparison with Anderson localization highlighting the superiority of the resonant phonons across both sides of the interference frequency limit.
- [11] arXiv:2406.04110 [pdf, ps, html, other]
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Title: Giant and anisotropic enhancement of spin-charge conversion in double Rashba interface graphene-based quantum systemAlberto Anadón, Armando Pezo, Iciar Arnay, Rubén Guerrero, Adrián Gudín, Jaafar Ghanbaja, Julio Camarero, Aurelien Manchon, Sebastien Petit-Watelot, Paolo Perna, Juan-Carlos Rojas-SánchezComments: 33 pages with double-spaced paragraphs. 23 pages without references. 4 figures and one extended figure. Supplementary information, not shown, contains 21 pages and 23 supplementary figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)
The ever-increasing demand for efficient data storage and processing has fueled the search for novel memory devices. Spintronics offers an alternative fast and efficient solution using spin-to-charge interconversion. In this work, we demonstrate a remarkable thirty-four-fold increase in spin-to-charge current conversion when incorporating a 2D epitaxial graphene monolayer between iron and platinum layers by exploring spin-pumping on-chip devices. Furthermore, we find that the spin conversion is also anisotropic. We attribute this enhancement and anisotropy to the asymmetric Rashba contributions driven by an unbalanced spin accumulation at the differently hybridized top and bottom graphene interfaces, as highlighted by ad-hoc first-principles theory. The improvement in spin-to-charge conversion as well as its anisotropy reveals the importance of interfaces in hybrid 2D-thin film systems opening up new possibilities for engineering spin conversion in 2D materials, leading to potential advances in memory, logic applications, or unconventional computing.
New submissions for Friday, 7 June 2024 (showing 11 of 11 entries )
- [12] arXiv:2406.03590 (cross-list from math-ph) [pdf, ps, html, other]
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Title: Quantum Mechanics of Particles Constrained to Spiral Curves with Application to Polyene ChainsSubjects: Mathematical Physics (math-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Context: Due to advances in synthesizing lower dimensional materials there is the challenge of finding the wave equation that effectively describes quantum particles moving on 1D and 2D domains. Jensen and Koppe and Da Costa independently introduced a confining potential formalism showing that the effective constrained dynamics is subjected to a scalar geometry-induced potential; for the confinement to a curve, the potential depends on the curve's curvature function.
Method: To characterize the $\pi$ electrons in polyenes, we follow two approaches. First, we utilize a weakened Coulomb potential associated with a spiral curve. The solution to the Schrödinger equation with Dirichlet boundary conditions yields Bessel functions, and the spectrum is obtained analytically. We employ the particle-in-a-box model in the second approach, incorporating effective mass corrections. The $\pi$-$\pi^*$ transitions of polyenes were calculated in good experimental agreement with both approaches, although with different wave functions. - [13] arXiv:2406.03598 (cross-list from cond-mat.supr-con) [pdf, ps, other]
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Title: Time reversal symmetry breaking and zero magnetic field Josephson diode effect in Dirac semimetal Cd3As2-mediated asymmetric SQUIDsSubjects: Superconductivity (cond-mat.supr-con); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)
A zero-magnetic-field Josephson diode effect (JDE) is observed in an asymmetric superconducting quantum interference device (SQUID) mediated by Dirac semimetal Cd3As2. Herein it is shown that phase coupling between the surface and bulk superconducting channels, a unique phenomenon recently identified in the observations of fractional Josephson effect and Leggett modes in Cd3As2, can break time reversal symmetry (TRS) and, therefore, give rise to the zero-field JDE. It is identified that the efficiency of the JDE can be readily controlled by varying the geometry of the Josephson junction (JJ) arms in the SQUIDs, thus providing an explanation of different JDE behaviors in two SQUIDs examined in this work. Our results are anticipated to have important implications in superconducting electronic circuit applications.
- [14] arXiv:2406.03602 (cross-list from cond-mat.mtrl-sci) [pdf, ps, other]
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Title: Capillary Flow Printing of Submicron Carbon Nanotube TransistorsBrittany N. Smith, Faris M. Albarghouthi, James L. Doherty, Xuancheng Pei, Quentin Macfarlane, Matthew Salfity, Daniel Badia, Marc Pascual, Pascal Boncenne, Nathan Bigan, Amin M'Barki, Aaron D. FranklinComments: 47 pages, 4 main text figures, 11 supporting info figuresSubjects: Materials Science (cond-mat.mtrl-sci); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Although printed transistors have a wide range of applications, the limited resolution of printing techniques (10-30 um) has been a barrier to advancement and scaling, particularly down to submicron dimensions. While previous works have shown creative approaches to realizing submicron channel lengths with printing, reliance on chemical processes unique to specific inks or tedious post-processing limit their applicability. Here, we report the use of capillary flow printing (CFP) to repeatably create fully printed submicron carbon nanotube thin-film transistors (CNT-TFTs) without chemical modification or physical manipulation post-printing. The versatility of this printing technique is demonstrated by printing conducting, semiconducting, and insulating inks on several types of substrates (SiO2, Kapton, and paper) and through the fabrication of various TFT device (contacting/gating) architectures. Notably, CFP of these CNT-TFTs yielded on-currents of 1.12 mA/mm when back gated on Si/SiO2, and 490 uA/mm when side gated through ion gel on Kapton, demonstrating the strong transistor performance achievable with CFP. Mechanical bending and sweep rate resilience of devices printed on Kapton show the wide utility of CFP-fabricated devices for flexible applications. This work highlights the ability of CFP as a viable fabrication method for submicron electronics through cleanroom-free printing techniques.
- [15] arXiv:2406.03627 (cross-list from quant-ph) [pdf, ps, html, other]
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Title: Optimal Control and Glassiness in Quantum SensingSubjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Atomic Physics (physics.atom-ph)
Quantum systems are powerful detectors with wide-ranging applications from scanning probe microscopy of materials to biomedical imaging. Nitrogen vacancy (NV) centers in diamond, for instance, can be operated as qubits for sensing of magnetic field, temperature, or related signals. By well-designed application of pulse sequences, experiments can filter this signal from environmental noise, allowing extremely sensitive measurements with single NV centers. Recently, optimal control has been used to further improve sensitivity by modification of the pulse sequence, most notably by optimal placement of $\pi$ pulses. Here we consider extending beyond $\pi$ pulses, exploring optimization of a continuous, time-dependent control field. We show that the difficulty of optimizing these protocols can be mapped to the difficulty of finding minimum free energy in a classical frustrated spin system. While most optimizations we consider show autocorrelations of the sensing protocol that grow as a power law -- similar to an Ising spin glass -- the continuous control shows slower logarithmic growth, suggestive of a harder Heisenberg-like glassy landscape.
- [16] arXiv:2406.03700 (cross-list from cond-mat.supr-con) [pdf, ps, other]
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Title: Ferroelectricity-tuned band topology and superconductivity in two-dimensional materials and related heterostructuresComments: Invited Review for Adv.Funct.Mater.,comments are welcomeSubjects: Superconductivity (cond-mat.supr-con); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Ferroelectricity, band topology, and superconductivity are respectively local, global, and macroscopic properties of quantum materials, and understanding their mutual couplings offers unique opportunities for exploring rich physics and enhanced functionalities. In this mini-review, we attempt to highlight some of the latest advances in this vibrant area, focusing in particular on ferroelectricity-tuned superconductivity and band topology in two-dimensional (2D) materials and related heterostructures. We will first present results from predictive studies of the delicate couplings between ferroelectricity and topology or superconductivity based on first-principles calculations and phenomenological modeling, with ferroelectricity-enabled topological superconductivity as an appealing objective. Next, we will cover the latest advances on experimental studies of ferroelectricity-tuned superconductivity based on different 2D materials or van der Waals heterostructures. Finally, as perspectives, we will outline schemes that may allow to materialize new types of 2D systems that simultaneously harbor ferroelectricity and superconductivity, or that may lead to enhanced ferroelectric superconductivity, ferroelectric topological superconductivity, and new types of superconducting devices such as superconducting diodes.
- [17] arXiv:2406.03876 (cross-list from physics.optics) [pdf, ps, other]
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Title: Time-resolved optical assessment of exciton formation in mixed two-dimensional perovskite filmsZheng Zhang, Jianan Wang, Yijie Shi, Xi Wang, Zhong Wang, Xiangyu Zhu, Chunlong Hu, Zonghao Liu, Wei Chen, Wenxi LiangComments: Main text: 15 pages, 4 figures. Supplementary Information: 16 pages, 16 figures, 10 tablesSubjects: Optics (physics.optics); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
We report the observation of exciton formation from the cooled band-edge carriers in mixed two-dimensional hybrid organic-inorganic perovskites using femtosecond transient absorption spectroscopy. By monitoring the changes of bleach signal upon excitations with various photon energy, we are able to extract the values of exciton binding energy and the occupancies of carriers of free and bound states for each two-dimensional phase. We also confirm the existence of Mahan exciton when injected carrier density is above the Mott criterion.
- [18] arXiv:2406.03925 (cross-list from cond-mat.stat-mech) [pdf, ps, html, other]
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Title: Topological phases in discrete stochastic systemsComments: Invited review for Reports on Progress in Physics, submitted. Comments welcomeSubjects: Statistical Mechanics (cond-mat.stat-mech); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Soft Condensed Matter (cond-mat.soft); Biological Physics (physics.bio-ph)
Topological invariants have proved useful for analyzing emergent function as they characterize a property of the entire system, and are insensitive to local details, disorder, and noise. They support edge states, which reduce the system response to a lower dimensional space and offer a mechanism for the emergence of global cycles within a large phase space. Topological invariants have been heavily studied in quantum electronic systems and been observed in other classical platforms such as mechanical lattices. However, this framework largely describes equilibrium systems within an ordered crystalline lattice, whereas biological systems are often strongly non-equilibrium with stochastic components. We review recent developments in topological states in discrete stochastic models in 1d and 2d systems, and initial progress in identifying testable signature of topological states in molecular systems and ecology. These models further provide simple principles for targeted dynamics in synthetic systems or in the engineering of reconfigurable materials. Lastly, we describe novel theoretical properties of these systems such as the necessity for non-Hermiticity in permitting edge states, as well as new analytical tools to reveal these properties. The emerging developments shed light on fundamental principles for non-equilibrium systems and topological protection enabling robust biological function.
- [19] arXiv:2406.03934 (cross-list from physics.optics) [pdf, ps, html, other]
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Title: Theory of photoluminescence by metallic structuresSubjects: Optics (physics.optics); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Light emission by metals at room temperature is quenched by fast relaxation processes. Nevertheless, Mooradian reported in 1969 the observation of photoluminescence by metals pumped by a laser. Strikingly, while it is currently at the heart of many promising applications, this phenomenon is still poorly understood. In this work, we report a theory which reproduces quantitatively previously published experimental data. We first provide a general formula that relates the emitted power for a frequency, direction and polarization state to a sum over all transitions involving matrix elements, electronic distribution of all bands and the Green tensor. We then consider the case of intraband recombination and derive a closed-form expression of the emitted power depending only on macroscopic quantities. This formula, which is a generalization of Kirchhoff's law, answers many of the open questions related to intraband photoluminescence.
- [20] arXiv:2406.04073 (cross-list from cond-mat.str-el) [pdf, ps, html, other]
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Title: Diagnosing Altermagnetic Phases through Quantum OscillationsComments: 6 pages, 4 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
The recently delimited altermagnetic phase is characterized by zero net magnetization but momentum-dependent collinear spin-splitting. To explore the intriguing physical effects and potential applications of altermagnets, it is essential to analyze their Fermi surface properties, encompassing both configurations and spin textures. Here, we conduct a Fermiology study on metallic altermagnets and demonstrate that the collinear spin-split features of their Fermi surfaces can be clearly revealed through quantum oscillation measurements. By introducing a transverse Zeeman field to remove the spin-degenerate lines in the momentum space, the Fermi surface undergoes a Lifshitz transition, giving rise to spin-flipped cyclotron motion between orbits with opposite spins. Accordingly, the Lifshitz-Onsager quantization yields two sets of Landau levels, leading to frequency splitting of the Shubnikov-de Haas oscillations in conductivity. In the presence of spin-orbit coupling, the Zeeman field causes two separate cyclotron orbits to merge at the Lifshitz transition point before splitting again. This results in the two original frequencies discontinuously changing into a single frequency equal to their sum. Our work unveils a unique and universal signature of altermagnetic Fermi surfaces that can be probed through quantum oscillation measurements.
- [21] arXiv:2406.04252 (cross-list from cond-mat.mtrl-sci) [pdf, ps, other]
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Title: Sub-nanometer depth resolution and single dopant visualization achieved by tilt-coupled multislice electron ptychographyZehao Dong, Yang Zhang, Chun-Chien Chiu, Sicheng Lu, Jianbing Zhang, Yu-Chen Liu, Suya Liu, Jan-Chi Yang, Pu Yu, Yayu Wang, Zhen ChenComments: 27 pages, 5 figures, 10 supplementary figuresSubjects: Materials Science (cond-mat.mtrl-sci); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Real-space imaging of three-dimensional atomic structures is a critical yet challenging task in materials science. Although scanning transmission electron microscopy has achieved sub-angstrom lateral resolution through techniques like electron ptychography1,2, depth resolution remains limited to only 2 to 3 nanometers with a single projection setup3,4. Attaining better depth resolution typically necessitates large sample tilt angles and many projections, as seen in atomic electron tomography5,6. Here, we develop a new algorithm based on multislice electron ptychography which couples only a few projections at small tilt angles, but is sufficient to improve the depth resolution by more than threefold to the sub-nanometer scale, and potentially to the atomic level. This technique maintains high resolving power for both light and heavy atoms, and significantly improves the visibility of single dopants. We are thus able to experimentally detect dilute substitutional praseodymium dopants in a brownmillerite oxide, Ca2Co2O5, in three dimensions and observe the accompanying lattice distortion. This technique requires only a moderate level of data acquisition or processing, and can be seamlessly integrated into electron microscopes equipped with conventional components.
Cross submissions for Friday, 7 June 2024 (showing 10 of 10 entries )
- [22] arXiv:2212.00199 (replaced) [pdf, ps, html, other]
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Title: Evidence of $\phi$0-Josephson junction from skewed diffraction patterns in Sn-InSb nanowiresB. Zhang, Z. Li, V. Aguilar, P. Zhang, M. Pendharkar, C. Dempsey, J. S. Lee, S. D. Harrington, S. Tan, J. S. Meyer, M. Houzet, C. J. Palmstrom, S. M. FrolovSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
We study Josephson junctions based on InSb nanowires with Sn shells. We observe skewed critical current diffraction patterns: the maxima in forward and reverse current bias are at different magnetic flux, with a displacement of 20-40 mT. The skew is greatest when the external field is nearly perpendicular to the nanowire, in the substrate plane. This orientation suggests that spin-orbit interaction plays a role. We develop a phenomenological model and perform tight-binding calculations, both methods reproducing the essential features of the experiment. The effect modeled is the $\phi$0-Josephson junction with higher-order Josephson harmonics. The system is of interest for Majorana studies: the effects are either precursor to or concomitant with topological superconductivity. Current-phase relations that lack inversion symmetry can also be used to design quantum circuits with engineered nonlinearity.
- [23] arXiv:2311.01321 (replaced) [pdf, ps, html, other]
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Title: Method of Mechanical Exfoliation of Bismuth with Micro-Trench StructuresOulin Yu, Raphaela Allgayer, Simon Godin, Jacob Lalande, Paolo Fossati, Chunwei Hsu, Thomas Szkopek, Guillaume GervaisJournal-ref: J. Appl. Phys. 134, 244302 (2023)Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)
The discovery of graphene led to a burst in search for 2D materials originating from layered atomic crystals coupled by van der Waals force. While bulk bismuth crystals share this layered crystal structure, unlike other group V members of the periodic table, its interlayer bonds are stronger such that traditional mechanical cleavage and exfoliation techniques have shown to be inefficient. In this work, we present a novel mechanical cleavage method for exfoliating bismuth by utilizing the stress concentration effect induced by micro-trench SiO2 structures. As a result, the exfoliated bismuth flakes can achieve thicknesses down to the sub-10 nm range which are analyzed by AFM and Raman spectroscopy.
- [24] arXiv:2401.10913 (replaced) [pdf, ps, html, other]
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Title: Symmetry-induced higher-order exceptional points in two dimensionsJournal-ref: Phys. Rev. Research 6, 023205 (2024)Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics); Quantum Physics (quant-ph)
Exceptional points of order $n$ (EP$n$s) appear in non-Hermitian systems as points where the eigenvalues and eigenvectors coalesce. They emerge if $2(n-1)$ real constraints are imposed, such that EP2s generically appear in two dimensions (2D). Local symmetries have been shown to reduce this number of constraints. In this work, we provide a complete characterization of the appearance of symmetry-induced higher-order EPs in 2D parameter space. We find that besides EP2s only EP3s, EP4s, and EP5s can be stabilized in 2D. Moreover, these higher-order EPs must always appear in pairs with their dispersion determined by the symmetries. Upon studying the complex spectral structure around these EPs, we find that depending on the symmetry, EP3s are accompanied by EP2 arcs, and two- and three-level open Fermi structures. Similarly, EP4s and closely related EP5s, which arise due to multiple symmetries, are accompanied by exotic EP arcs and open Fermi structures. For each case, we provide an explicit example. We also comment on the topological charge of these EPs, and discuss similarities and differences between symmetry-protected higher-order EPs and EP2s.
- [25] arXiv:2402.18441 (replaced) [pdf, ps, html, other]
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Title: Anomalous Hall Effect in Thin BismuthSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Bismuth, the heaviest of all group V elements with strong spin-orbit coupling, is famously known to exhibit many interesting transport properties, and effects such as Shubnikov-de Haas and de Haas-van Alphen were first revealed in its bulk form. However, the transport properties have not yet been fully explored experimentally in thin bismuth nor in its 2D limit. In this work, bismuth flakes with average thicknesses ranging from 29 to 69 nm were mechanically exfoliated by a micro-trench technique and were used to fabricate four-point devices. Due to mixing of components, Onsager's relations were used to extract the longitudinal ($R_{xx}$) and Hall ($R_{xy}$) resistances where the latter shows a Hall anomaly that is consistent with the Anomalous Hall Effect (AHE). Our work strongly suggests that that there could be a hidden mechanism for time-reversal symmetry breaking in pure bismuth thin films.
- [26] arXiv:2404.05485 (replaced) [pdf, ps, html, other]
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Title: Many-body quantum dynamics of spin-orbit coupled Andreev states in a Zeeman fieldComments: 18 pages, 11 figuresJournal-ref: Physical Review B 109, 214505 (2024)Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Superconductivity (cond-mat.supr-con)
We provide a theoretical framework to describe the quantum many-body dynamics of Andreev states in Josephson junctions with spin-orbit coupling and a magnetic Zeeman field. In such cases, employing a doubled Nambu spinor description is technically advantageous but one then has to be careful to avoid double-counting problems. By deriving the Lindblad master equation in the socalled excitation picture, we show that a physically consistent many-body theory free from doublecounting problems follows. We apply our formalism to a study of dynamical parity stabilization of the Andreev sector at intermediate times after an initial microwave pulse, in particular addressing the combined effects of spin-orbit coupling and Zeeman field.
- [27] arXiv:2405.11641 (replaced) [pdf, ps, html, other]
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Title: Time depending magnetization of nanoparticles under radiofrequency fields: Experimental relaxation time in water for solid-liquid transitionSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
In application as hyperthermia and nanowarming, power dissipation arises when the time-dependent magnetization $M(t)$ of an out-of-equilibrium system of nanoparticles lags behind the applied field $H(t)$. The key parameter governing this process is the relaxation time $\tau$ of the system, which induces a phase shift $\phi_n$ between $H(t)$ and every nth harmonic component of $M(t)$. In this work, we present an expression for $M(t)$ in terms of $\tau$ and the equilibrium magnetization, valid for any magnetic system exhibiting odd equilibrium response. From this calculation, we obtain a method for determining the effective $\tau$ of a MNPs sample directly from the experimental measurement of $M(t)$. Additionally, we demonstrate that the power dissipation (SAR: Specific Absorption Rate) of any magnetic sample under a sinusoidal field can be obtained from the first harmonic component of $M(t)$. As an illustrative application, we explore the variation of $\tau$ for magnetic MNPs in aqueous suspension during the melting process of the matrix. In this case, the change in $\tau$ can be understood as a result of the reorientation of the MNPs in the direction of the applied field as the matrix becomes liquid.
- [28] arXiv:2403.14249 (replaced) [pdf, ps, other]
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Title: Direct Probe of Topology and Geometry of Quantum States on IBM QComments: 14 pages, 8 figures (updated main text and references)Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
The concepts of topology and geometry are of critical importance in exploring exotic phases of quantum matter. Though they have been investigated on various experimental platforms, to date a direct probe of topological and geometric properties on a universal quantum computer even for a minimum model is still in vain. In this work, we first show that a density matrix form of the quantum geometric tensor (QGT) can be explicitly re-constructed from Pauli operator measurements on a quantum circuit. We then propose two algorithms, suitable for IBM quantum computers, to directly probe QGT. The first algorithm is a variational quantum algorithm particularly suitable for Noisy Intermediate-Scale Quantum (NISQ)-era devices, whereas the second one is a pure quantum algorithm based on quantum imaginary time evolution. Explicit results obtained from IBM Q simulating a Chern insulator model are presented and analysed. Our results indicate that transmon qubit-based universal quantum computers have the potential to directly simulate and investigate topological and geometric properties of a quantum system.