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Flat-band full localization and symmetry-protected topological phase on bilayer lattice systems

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arXiv 2021年

作者： Ichinose, Ikuo Orito, Takahiro Kuno, Yoshihito Department of Applied Physics Nagoya Institute of Technology Nagoya466-8555 Japan Quantum Matter program Graduate School of Advanced Science and Engineering Hiroshima University Higashi-Hiroshima739-8530 Japan Department of Physics Graduate School of Science Tsukuba University Ibaraki Tsukuba305-8571 Japan

In this work, we present bilayer flat-band Hamiltonians, in which all bulk states are localized and specified by extensive local integrals of motion (LIOMs). The present systems are bilayer extension of Creutz ladder, which is studied previously. In order to construct models, we employ building blocks, cube operators, which are linear combinations of fermions defined in each cube of the bilayer lattice. There are eight cubic operators, and the Hamiltonians are composed of the number operators of them, the LIOMs. A suitable arrangement of locations of the cube operators is needed to have exact projective Hamiltonians. The projective Hamiltonians belong to a topological classification class, BDI class. With the open boundary condition, the constructed Hamiltonians have gapless edge modes, which commute with each other as well as the Hamiltonian. This result comes from a symmetry analogous to the one-dimensional chiral symmetry of the BDI class. These results indicate that the projective Hamiltonians describe a kind of symmetry protected topological phase matter. Careful investigation of topological indexes, such as Berry phase, string operator, is given. We also show that by using the gapless edge modes, a generalized Sachdev-Ye-Kitaev (SYK) model is constructed. © 2021, CC BY.

关键词： Hamiltonians

Cavity-mediated superthermal phonon correlations in the ultrastrong coupling regime

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arXiv 2024年

作者： Kim, Dasom Hou, Jin Lee, Geon Agrawal, Ayush Kim, Sunghwan Zhang, Hao Bao, Di Baydin, Andrey Wu, Wenjing Tay, Fuyang Huang, Shengxi Chia, Elbert E.M. Kim, Dai-Sik Seo, Minah Mohite, Aditya D. Hagenmüller, David Kono, Junichiro Applied Physics Graduate Program Smalley–Curl Institute Rice University HoustonTX77005 United States Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States Sensor System Research Center Korea Institute of Science and Technology Seoul02792 Korea Republic of Department of Physics and Astronomy Seoul National University Seoul08826 Korea Republic of Department of Chemical and Biomolecular Engineering Rice University Houston77005 United States Ulsan44919 Korea Republic of Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore637371 Singapore Smalley–Curl Institute Rice University HoustonTX77005 United States Rice Advanced Materials Institute Rice University HoustonTX77005 United States KU–KIST Graduate School of Converging Science and Technology Korea University Seoul02841 Korea Republic of Université de Strasbourg CNRS Strasbourg67200 France Department of Physics and Astronomy Rice University HoustonTX77005 United States

Phonons, or vibrational quanta, are behind some of the most fundamental physical phenomena in solids, including superconductivity, Raman processes, and broken-symmetry phases. It is therefore of fundamental importance to find ways to harness phonons for controlling these phenomena and developing novel quantum technologies. However, the majority of current phonon control techniques rely on the use of intense external driving fields or strong anharmonicities, which restricts their range of applications. Here, we present a scheme for controlling the intensity fluctuations in phonon emission at room temperature based on multimode ultrastrong light–matter coupling. The multimode ultrastrong coupling regime is achieved by coupling two optical phonon modes in lead halide perovskites to an array of nanoslots, which operates as a single-mode cavity. The extremely small mode volume of the nanoslots enables unprecedented coupling strengths in a cavity phonon-polariton system. In the far-detuned, low-cavity-frequency regime, we demonstrate that the nanoslot resonator mediates an effective coupling between the phonon modes, resulting in superthermal phonon bunching in thermal equilibrium, both within the same mode and between different modes. Experimental results are in good agreement with a multimode Hopfield model. Our work paves the way for the tailoring of phonons to modify charge and energy transport in perovskite materials, with potential applications in light-collecting or emitting devices. Copyright © 2024, The Authors. All rights reserved.

关键词： Perovskite

Deep learning inter-atomic potential for thermal and phonon behaviour of silicon carbide with quantum accuracy

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arXiv 2021年

作者： Fu, Baoqin Sun, Yandong Zhang, Linfeng Wang, Han Xu, Ben Key Laboratory of Radiation Physics and Technology of the Ministry of Education Institute of Nuclear Science and Technology Sichuan University Chengdu610064 China Graduate School China Academy of Engineering Physics Beijing100193 China Program in Applied and Computational Mathematics Princeton University PrincetonNJ United States Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China

Silicon carbide (SiC) is an essential material for next generation semiconductors and components for nuclear plants. It’s applications are strongly dependent on its thermal conductivity, which is highly sensitive to microstructures. Molecular dynamics (MD) simulation is the most used methods to address thermal transportation mechanisms in devices or microstructures of nano-meters. However, the implementation of MD is limited in SiC because of lacking accurate inter-atomic potentials. In this work, using the Deep Potential (DP) methodology, we developed two inter-atomic potentials (DP-*Corresponding author. IAPs) for SiC based on two adaptively generated datasets within the density functional approximations at the local density and the generalized gradient levels. These two DP-IAPs manifest their speed with quantum accuracy in lattice dynamics simulations as well as scattering rate analysis of phonon transportation. Combining with molecular dynamics simulations, the thermal transport and mechanical properties were systematically investigated. The presented methodology and the inter-atomic potentials pave the way for a systematic approach to model heat transport in SiC related devices using multiscale modelling. Copyright © 2021, The Authors. All rights reserved.

关键词： Silicon carbide

Magneto-optical Spectroscopy with RAMBO: A Table-Top 30 T Magnet

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arXiv 2022年

作者： Tay, Fuyang Baydin, Andrey Katsutani, Fumiya Kono, Junichiro Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Physics and Astronomy Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

Optically probing materials in high magnetic fields can provide enlightening insight into field-modified electronic states and phases, while optically driving materials in high magnetic fields can induce novel nonequilibrium many-body dynamics of spin and charge carriers. While there are high-field magnets compatible with standard optical spectroscopy methods, they are generally bulky and have limited optical access, which prohibit performing state-of-the-art ultrafast and/or nonlinear optical experiments. The Rice Advanced Magnet with Broadband Optics (RAMBO), a unique 30-T pulsed mini-coil magnet system with direct optical access, has enabled previously challenging experiments using femtosecond optical pulses, including time-domain terahertz spectroscopy, in cutting-edge materials placed in strong magnetic fields. Here, we review recent experimental advances made possible by the first-generation RAMBO setup. After summarizing technological aspects of combining optical spectroscopic techniques with the mini-coil magnet, we describe results of magneto-optical studies of a wide variety of materials, providing new insight into the states and dynamics of four types of quasiparticles in solids – excitons, plasmons, magnons, and phonons – in high magnetic fields. Copyright © 2022, The Authors. All rights reserved.

关键词： Magnets

The effect of loops on the mean square displacement of Rouse-model chromatin

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arXiv 2023年

作者： Yuan, Tianyu Yan, Hao Bailey, Mary Lou P. Williams, Jessica F. Surovtsev, Ivan King, Megan C. Mochrie, Simon G.J. Integrated Graduate Program in Physical and Engineering Biology Yale University New HavenCT06520 United States Department of Physics Yale University New HavenCT06520 United States Department of Applied Physics Yale University New HavenCT06520 United States Department of Cell Biology Yale School of Medicine New HavenCT06520 United States Department of Molecular Cell and Developmental Biology Yale University New HavenCT06511 United States

Chromatin exhibits polymer properties and its dynamics are now commonly described using the classical Rouse model. The subsequent discovery, however, of intermediate scale chromatin organization known as topologically associating domains (TADs) in experimental Hi-C contact maps for chromosomes across the tree of life, together with the proposed loop extrusion factor (LEF) model that aims to explain TAD formation, motivates efforts to understand the effect of loops and loop extrusion on chromatin dynamics. This paper seeks to fulfill this need by combining LEF-model simulations with extended Rouse-model polymer simulations to investigate the dynamics of chromatin with loops and dynamic loop extrusion. Specifically, we extend the classical Rouse model by modifying the polymer's dynamical matrix to incorporate extra springs that represent loop bases. We also theoretically generalize the friction coefficient matrix so that the Rouse beads with nonuniform friction coefficients are compatible with our Rouse model simulation method. We show that loops significantly suppress the averaged mean square displacement (MSD) of a gene locus, consistent with recent experiments that track fluorescently-labelled chromatin loci. We also find that loops reduce the MSD's stretching exponent from the classical Rouse-model value of 1/2 to a loop-density-dependent value in the 0.45-0.40 range. Remarkably, stretching exponent values in this range have also been observed in recent experiments [S. C. Weber, A. J. Spakowitz, and J. A. Theriot, Phys. Rev. Lett. 104, 238102 (2010) and M. L. P. Bailey, I. Surovtsev, J. F. Williams, H. Yan, T. Yuan, S. G. Mochrie, and M. C. King, Mol. Biol. Cell (in press)]. We also show that for a wide range of plausible loop-extrusion parameters, the dynamics of loop extrusion itself negligibly affects chromatin mobility. By studying a static "rosette" loop configuration, we also demonstrate that chromatin MSDs and stretching exponents depend on the location of

关键词： Extrusion

Structural, optical, and thermal properties of BN thin films grown on diamond via pulsed laser deposition

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Physical Review Materials 2023年第9期7卷 094602-094602页

作者： Abhijit Biswas Gustavo A. Alvarez Tao Li Joyce Christiansen-Salameh Eugene Jeong Anand B. Puthirath Sathvik Ajay Iyengar Chenxi Li Tia Gray Xiang Zhang Tymofii S. Pieshkov Harikishan Kannan Jacob Elkins Robert Vajtai A. Glen Birdwell Mahesh R. Neupane Elias J. Garratt Bradford B. Pate Tony G. Ivanov Yuji Zhao Zhiting Tian Pulickel M. Ajayan Department of Materials Science and Nanoengineering Rice University Houston Texas 77005 USA Sibley School of Mechanical and Aerospace Engineering Cornell University Ithaca New York 14853 USA Department of Electrical and Computer Engineering Rice University Houston Texas 77005 USA Applied Physics Graduate Program Smalley-Curl Institute Rice University Houston Texas 77005 USA DEVCOM Army Research Laboratory RF Devices and Circuits Adelphi Maryland 20783 USA Naval Research Laboratory Chemistry Division Washington District of Columbia 20375 USA

Heterostructures based on ultrawide-bandgap (UWBG) semiconductors (bandgap>4.0eV), such as BN and diamond, hold significant importance for the development of high-power electronics in the next generation. However, achieving in situ heteroepitaxy of BN/diamond or vice versa remains exceptionally challenging due to the complex growth kinetics involved. In this work, we grew BN thin film on (100) single-crystal diamonds using pulsed laser deposition and investigated its structural, magnetic, optical, and thermal properties. The structural analyses confirmed the growth of BN films, which exhibited diamagnetic behavior at room temperature. Notably, the film demonstrated anisotropic refractive index characteristics within the visible-to-near-infrared wavelength range. The room-temperature cross-plane thermal conductivity of BN is 1.53 ± 0.77 W/mK, while the thermal conductance of the BN/diamond interface is 20±2MW/m2K. These findings have significant implications for a range of device applications based on UWBG BN/diamond heterostructures.

关键词： Growth Thermal conductivity Boron nitride Thin films Wide band gap systems Film deposition Laser ablation Thermoreflectance

Cementing the grain boundary defects in the strain relaxed mixed Sn-Pb perovskite solar cells

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Chemical Engineering Journal 2025年 516卷

作者： Kumar, Abhishek Ansari, Zeeshan Alam Hanmandlu, Chintam Banerjee, Soumallya Chen, Yu-Te Yang, Po-Yu Musa, Ahmed Fouad You, Yun-Wen Pao, Chun-Wei Wei, Tzu-Chien Shyue, Jing-Jong Lu, Yu-Jung Chu, Chih-Wei Department of Physics National Taiwan University Sec. 4 Roosevelt Road Taipei106 Taiwan Research Center for Applied Sciences Academia Sinica 128 Academia Road Section 2 Taipei Nangang11529 Taiwan Nano-Science and Technology Program Taiwan International Graduate Program Academia Sinica Taipei106 Taiwan Department of Materials Science and Engineering National Yang Ming Chiao Tung University Hsinchu300 Taiwan Department of Chemical Engineering National Tsing Hua University 101 Section 2 Kuang-Fu Road Hsinchu City300044 Taiwan College of Engineering Center for Green Technology Chang Gung University Taoyuan City333002 Taiwan Department of Photonics National Yang Ming Chiao Tung University Hsinchu City30010 Taiwan Institute of Applied Mechanics National Taiwan University Sec. 4 Roosevelt Road Taipei106 Taiwan

Mixed Tin-lead (Sn-Pb) perovskite solar cells (PSCs) offer a promising avenue for achieving high power conversion efficiencies (PCEs) due to their narrow bandgaps and substantial optical absorption in the visible–near-infrared region. However, the disparated reaction kinetics of PbI2 and SnI2 with organic salts, resulting in an uneven spatial distribution of Sn2+ and Pb2+ within the perovskite lattice, inducing micro-strain in the film and a Sn-rich surface vulnerable to oxidation-Sn2+ to Sn4+, thereby elevating nonradiative recombination. Here, we report the incorporation of 2,5-Dibromo-3,4-pyridinediamine (DBPDA) as an additive in the mixed Sn-Pb perovskite precursor solution, designed to mitigate micro-strain formation, reduce defect density by suppressing Sn4+ formation, and enhance the passivation of undercoordinated Sn/Pb species through synergistic bonding interaction. The best performing PSCs achieved an impressive PCE of 21.24 % with a high open circuit voltage (Voc) of 0.85 V, alongside significantly improved long-term stability, retaining near 80 % of their initial PCE after 1,008 h in a nitrogen-filled glovebox without encapsulation. In contrast, the control devices retained only 18 % of their initial efficiency under identical conditions. Additionally, an enhanced field effect hole mobility, increasing from 0.18 cm2/V-s in the control film to 1.43 cm2/V-s in the target film, was achieved in mixed Sn-Pb perovskite thin film transistors (TFTs) using these films as active layers. These findings present a viable strategy for strain-relieved perovskite films, enabling stable and high-performance mixed Sn-Pb PSCs and TFTs. © 2025 Elsevier B.V.

关键词： Crystallization kinetics

Covariance distributions in single particle tracking

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Physical Review E 2021年第3期103卷 032405-032405页

作者： Mary Lou P. Bailey Hao Yan Ivan Surovtsev Jessica F. Williams Megan C. King Simon G. J. Mochrie Integrated Graduate Program in Physical and Engineering Biology Yale University New Haven Connecticut 06520 USA Department of Applied Physics Yale University New Haven Connecticut 06520 USA Department of Physics Yale University New Haven Connecticut 06520 USA Department of Cell Biology Yale School of Medicine New Haven Connecticut 06520 USA

Several recent experiments, including our own experiments in the fission yeast, Schizosaccharomyces pombe, have characterized the motions of gene loci within living nuclei by measuring the locus position over time, then proceeding to obtain the statistical properties of this motion. To address the question of whether a population of such single-particle tracks, obtained from many different cells, corresponds to a single mode of diffusion, we derive theoretical equations describing the probability distribution of the displacement covariance, assuming the displacement itself is a zero-mean multivariate Gaussian random variable. We also determine the corresponding theoretical means, variances, and third central moments. Bolstering the theory is good agreement between its predictions and the results obtained for various simulated and measured data sets, including simulated particle trajectories undergoing simple and anomalous diffusion, and the measured trajectories of an optically trapped bead in water, and in a viscoelastic polymer solution. We also show that, for sufficiently long tracks, each covariance distribution in all of these examples is well-described by a skew-normal distribution with mean, variance, and skewness given by the theory. However, for the experimentally measured motion of a gene locus in S. pombe, we find that the first two covariance distributions are wider than predicted, although the third and subsequent covariance distributions are well-described by theory. This observation suggests that the origin of the theory-experiment discrepancy in this case is associated with localization noise, which influences only the first two covariances. Thus, we hypothesized that the discrepancy is caused by locus-to-locus heterogeneity in the localization noise, of independent measurements of the same tagged site. Indeed, simulations implementing heterogeneous localization noise revealed that the excess covariance widths can be largely recreated on the basis of

关键词： Genetic processes Brownian dynamics Single molecule techniques

Anisotropy as a diagnostic test for distinct tensor-network wave functions of integer- and half-integer-spin Kitaev quantum spin liquids

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Physical Review B 2021年第2期104卷 024417-024417页

作者： Hyun-Yong Lee Takafumi Suzuki Yong Baek Kim Naoki Kawashima Department of Applied Physics Graduate School Korea University Sejong 30019 Korea Division of Display and Semiconductor Physics Korea University Sejong 30019 Korea Interdisciplinary Program in E·ICT-Culture-Sports Convergence Korea University Sejong 30019 Korea Graduate School for Engineering University of Hyogo Himeji Hyogo 670-2280 Japan Department of Physics University of Toronto Toronto Ontario M5S 1A7 Canada Institute for Solid State Physics University of Tokyo Kashiwa Chiba 277-8581 Japan

Contrasting ground states of quantum magnets with the integer- and half-integer-spin moments are the manifestation of many-body quantum interference effects. In this work, we investigate the distinct nature of the integer- and half-integer-spin quantum spin liquids in the framework of the Kitaev's model on the honeycomb lattice. The models with arbitrary spin quantum numbers are not exactly solvable in contrast to the well-known quantum spin liquid solution of the spin-1/2 system. We use the tensor-network wave functions for the integer-and half-integer-spin quantum spin liquid states to unveil the important difference between these states. We find that the distinct sign structures of the tensor-network wave function for the integer- and half-integer-spin quantum spin liquids are responsible for completely different ground states in the spatially anisotropic limit. Hence the spatial anisotropy would be a useful diagnostic test for distinguishing these quantum spin liquid states, both in the numerical computations and experiments on real materials. We support this discovery via extensive numerics including the tensor-network, DMRG, and exact diagonalization computations.

关键词： Quantum spin liquid Topological phases of matter Density matrix renormalization group Exact diagonalization Kitaev model Tensor network methods Tensor network renormalization