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Ultrafast creation and melting of nonequilibrium excitonic condensates in bulk WSe2 非平衡态激子凝聚体WSe2的超快生成和熔化
arXiv: Mesoscale and Nanoscale Physics Pub Date : 2020-11-24 DOI: 10.1103/PhysRevB.103.L241404
E. Perfetto, G. Stefanucci
{"title":"Ultrafast creation and melting of nonequilibrium excitonic condensates in bulk \u0000WSe2","authors":"E. Perfetto, G. Stefanucci","doi":"10.1103/PhysRevB.103.L241404","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.L241404","url":null,"abstract":"We study the screened dynamics of the nonequilibrium excitonic consensate forming in a bulk WSe$_{2}$ when illuminated by coherent light resonant with the lowest-energy exciton. Intervalley scattering causes electron migration from the optically populated K valley to the conduction band minimum at $Sigma$. Due to the electron-hole unbalance at the K point a plasma of quasi-free holes develops, which efficiently screens the interaction of the remaining excitons. We show that this plasma screening causes an ultrafast melting of the nonequilibrium consensate and that during melting coherent excitons and quasi-free electron-hole pairs coexist. The time-resolved spectral function does exhibit a conduction and excitonic sidebands of opposite convexity and relative spectral weight that changes in time. Both the dependence of the time-dependent conduction density on the laser intensity and the time-resolved spectral function agree with recent experiments.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86023041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 3
Simulating higher-order topological insulators in density wave insulators 密度波绝缘子中高阶拓扑绝缘子的模拟
arXiv: Mesoscale and Nanoscale Physics Pub Date : 2020-11-24 DOI: 10.1103/PhysRevB.103.245107
Kuan-Sen Lin, B. Bradlyn
{"title":"Simulating higher-order topological insulators in density wave insulators","authors":"Kuan-Sen Lin, B. Bradlyn","doi":"10.1103/PhysRevB.103.245107","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.245107","url":null,"abstract":"Since the discovery of the Harper-Hofstadter model, it has been known that condensed matter systems with periodic modulations can be promoted to non-trivial topological states with emergent gauge fields in higher dimensions. In this work, we develop a general procedure to compute the gauge fields in higher dimensions associated to low-dimensional systems with periodic (charge- and spin-) density wave modulations. We construct two-dimensional (2D) models with modulations that can be promoted to higher-order topological phases with $U(1)$ and $SU(2)$ gauge fields in 3D. Corner modes in our 2D models can be pumped by adiabatic sliding of the phase of the modulation, yielding hinge modes in the promoted models. We also examine a 3D Weyl semimetal (WSM) gapped by charge-density wave (CDW) order, possessing quantum anomalous Hall (QAH) surface states. We show that this 3D system is equivalent to a 4D nodal line system gapped by a $U(1)$ gauge field with a nonzero second Chern number. We explain the recently identified interpolation between inversion-symmetry protected phases of the 3D WSM gapped by CDWs using the corresponding 4D theory. Our results can extend the search for (higher-order) topological states in higher dimensions to density wave systems.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85768935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 4
Drive dependence of the Hall angle for a sliding Wigner crystal in a magnetic field 磁场中滑动维格纳晶体霍尔角的驱动依赖性
arXiv: Mesoscale and Nanoscale Physics Pub Date : 2020-11-24 DOI: 10.1103/PHYSREVB.103.125107
C. Reichhardt, C. Reichhardt
{"title":"Drive dependence of the Hall angle for a sliding Wigner crystal in a magnetic field","authors":"C. Reichhardt, C. Reichhardt","doi":"10.1103/PHYSREVB.103.125107","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.125107","url":null,"abstract":"We numerically examine the depinning and sliding dynamics of a Wigner crystal in the presence of quenched disorder and a magnetic field. In the disorder-free limit, the Wigner crystal Hall angle is independent of crystal velocity, but when disorder is present, we find that Hall angle starts near zero at the depinning threshold and increases linearly with increasing drive before reaching a saturation close to the disorder free value at the highest drives. The drive dependence is the result of a side jump effect produced when the charges move over pinning sites. The magnitude of the side jump is reduced at the higher velocities. The drive dependent Hall angle is robust for a wide range of disorder parameters and should be a generic feature of classical charges driven in the presence of quenched disorder and a magnetic field.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86731250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 4
Revealing defect-induced spin disorder in nanocrystalline Ni 揭示Ni纳米晶中缺陷诱导的自旋紊乱
arXiv: Mesoscale and Nanoscale Physics Pub Date : 2020-11-23 DOI: 10.1103/PHYSREVMATERIALS.5.044409
M. Bersweiler, Evelyn Pratami Sinaga, I. Peral, N. Adachi, P. Bender, N. Steinke, E. Gilbert, Y. Todaka, A. Michels, Y. Oba
{"title":"Revealing defect-induced spin disorder in nanocrystalline Ni","authors":"M. Bersweiler, Evelyn Pratami Sinaga, I. Peral, N. Adachi, P. Bender, N. Steinke, E. Gilbert, Y. Todaka, A. Michels, Y. Oba","doi":"10.1103/PHYSREVMATERIALS.5.044409","DOIUrl":"https://doi.org/10.1103/PHYSREVMATERIALS.5.044409","url":null,"abstract":"We use magnetic small-angle neutron scattering to study the magnetic microstructure of a nanocrystalline Ni bulk sample, which was prepared by straining via high-pressure torsion. The neutron data reveal that the scattering is strongly affected by the high density of crystal defects inside the sample, which were created by the severe plastic deformation during the sample preparation. The defects cause a significant spin-misalignment scattering contribution. The corresponding magnetic correlation length, which characterizes the spatial magnetization fluctuations in real space, indicates an average defect size of 11 nm. In the remanent state, the stray fields around the defects cause spin disorder in the surrounding ferromagnetic bulk, with a penetration depth of around 22 nm. The range and amplitude of the disorder is systematically suppressed by an increasing external magnetic field. Our findings are supported by micromagnetic simulations, which, for the particular case of nonmagnetic defects (holes) embedded in a ferromagnetic Ni phase, further highlight the role of localized spin perturbations for the magnetic microstructure of defect-rich magnets such as high-pressure torsion materials.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75796985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 6
Double Dirac cones and topologically nontrivial phonons for continuous square symmetric C4(v) and C2(v) unit cells 连续方形对称C4(v)和C2(v)单元格的双狄拉克锥和拓扑非平凡声子
arXiv: Mesoscale and Nanoscale Physics Pub Date : 2020-11-20 DOI: 10.1103/PHYSREVB.103.064308
Yan Lu, Harold S. Park
{"title":"Double Dirac cones and topologically nontrivial phonons for continuous square symmetric \u0000C4(v)\u0000 and \u0000C2(v)\u0000 unit cells","authors":"Yan Lu, Harold S. Park","doi":"10.1103/PHYSREVB.103.064308","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.064308","url":null,"abstract":"Because phononic topological insulators have primarily been studied in discrete, graphene-like structures with C$_{6}$ or C$_{3}$ hexagonal symmetry, an open question is how to systematically achieve double Dirac cones and topologically non-trivial structures using continuous, non-hexagonal unit cells. Here, we address this challenge by presenting a novel computational methodology for the inverse design of continuous two-dimensional square phononic metamaterials exhibiting C$_{4v}$ and C$_{2v}$ symmetry. This leads to the systematic design of square unit cell topologies exhibiting a double Dirac degeneracy, which enables topologically-protected interface propagation based on the quantum spin Hall effect (QSHE). Numerical simulations prove that helical edge states emerge at the interface between two topologically distinct square phononic metamaterials, which opens the possibility of QSHE-based pseudospin-dependent transport beyond hexagonal lattices.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80723839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 5
Coupling spins to nanomechanical resonators: Toward quantum spin-mechanics 耦合自旋到纳米力学谐振器:走向量子自旋力学
arXiv: Mesoscale and Nanoscale Physics Pub Date : 2020-11-19 DOI: 10.1063/5.0024001
Hailin Wang, I. Lekavicius
{"title":"Coupling spins to nanomechanical resonators: Toward quantum spin-mechanics","authors":"Hailin Wang, I. Lekavicius","doi":"10.1063/5.0024001","DOIUrl":"https://doi.org/10.1063/5.0024001","url":null,"abstract":"Spin-mechanics studies interactions between spin systems and mechanical vibrations in a nanomechanical resonator and explores their potential applications in quantum information processing. In this tutorial, we summarize various types of spin-mechanical resonators and discuss both the cavity-QED-like and the trapped-ion-like spin-mechanical coupling processes. The implementation of these processes using negatively charged nitrogen vacancy and silicon vacancy centers in diamond is reviewed. Prospects for reaching the full quantum regime of spin-mechanics, in which quantum control can occur at the level of both single spin and single phonon, are discussed with an emphasis on the crucial role of strain coupling to the orbital degrees of freedom of the defect centers.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82853859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 25
Quantum-limit Hall effect with large carrier density in topological semimetals 拓扑半金属中大载流子密度的量子极限霍尔效应
arXiv: Mesoscale and Nanoscale Physics Pub Date : 2020-11-19 DOI: 10.1103/PhysRevB.103.L241104
Guang Yang, Yi Zhang
{"title":"Quantum-limit Hall effect with large carrier density in topological semimetals","authors":"Guang Yang, Yi Zhang","doi":"10.1103/PhysRevB.103.L241104","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.L241104","url":null,"abstract":"The quantum-limit Hall effect at $nu = nh/eBsim O(1)$ that hosts a variety of exotic quantum phenomena requires demanding strong magnetic field $B$ and low carrier density $n$. We propose to realize quantum-limit Hall effect even in the presence of large carrier density residues $n_e$ and $n_h$ relative to the magnetic field $B$ in topological semimetals, where a single Fermi surface contour allow both electron-type and hole-type carriers and approaches charge neutrality as $n_esim n_h$. The underlying filling factor $nu = |n_e-n_h|h/eB$ explicitly violates the Onsager's relation for quantum oscillations.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76371458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Advances in dynamic AFM: From nanoscale energy dissipation to material properties in the nanoscale 动态AFM研究进展:从纳米尺度的能量耗散到纳米尺度的材料特性
arXiv: Mesoscale and Nanoscale Physics Pub Date : 2020-11-19 DOI: 10.1063/5.0041366
Sergio Santos, K. Gadelrab, Chia-Yun Lai, Tuza A. Olukan, J. Font, V. Barcons, A. Verdaguer, M. Chiesa
{"title":"Advances in dynamic AFM: From nanoscale energy dissipation to material properties in the nanoscale","authors":"Sergio Santos, K. Gadelrab, Chia-Yun Lai, Tuza A. Olukan, J. Font, V. Barcons, A. Verdaguer, M. Chiesa","doi":"10.1063/5.0041366","DOIUrl":"https://doi.org/10.1063/5.0041366","url":null,"abstract":"Since the inception of the atomic force microscope AFM, dynamic methods have been very fruitful by establishing methods to quantify dissipative and conservative forces in the nanoscale and by providing a means to apply gentle forces to the samples with high resolution. Here we review developments that cover over a decade of our work on energy dissipation, phase contrast and the extraction of relevant material properties from observables. We describe the attempts to recover material properties via one dimensional amplitude and phase curves from force models and explore the evolution of these methods in terms of force reconstruction, fits of experimental measurements, and the more recent advances in multifrequency AFM.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73412635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 10
Reduced quantum electrodynamics in curved space 弯曲空间中的简化量子电动力学
arXiv: Mesoscale and Nanoscale Physics Pub Date : 2020-11-18 DOI: 10.1103/PHYSREVD.103.065010
P. Caneda, G. Menezes
{"title":"Reduced quantum electrodynamics in curved space","authors":"P. Caneda, G. Menezes","doi":"10.1103/PHYSREVD.103.065010","DOIUrl":"https://doi.org/10.1103/PHYSREVD.103.065010","url":null,"abstract":"The physics of graphene has provided an important connection between quantum field theory and condensed-matter physics due to the particular features of the graphene quasiparticles which can be described as massless two-dimensional Dirac fermions. An approach that has been given promising results in this context is the reduced quantum electrodynamics. In this work we consider the natural generalization of this formalism to curved spaces. As an application, we calculate the one-loop optical conductivity of graphene taking into account the presence of ripples. Such ripples are modeled by curvature effects which can be incorporated by taking into account a suitable chemical potential. In addition, we demonstrate how such effects may contribute to a decisive increase in the minimal conductivity.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88082251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Electrically induced strong modulation of magnon transport in ultrathin magnetic insulator films 超薄磁绝缘体薄膜中磁振子输运的电诱导强调制
arXiv: Mesoscale and Nanoscale Physics Pub Date : 2020-11-16 DOI: 10.1103/PhysRevB.103.214425
Jian Liu, X. Wei, Gerrit E. W. Bauer, J. Youssef, B. V. Wees
{"title":"Electrically induced strong modulation of magnon transport in ultrathin magnetic insulator films","authors":"Jian Liu, X. Wei, Gerrit E. W. Bauer, J. Youssef, B. V. Wees","doi":"10.1103/PhysRevB.103.214425","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.214425","url":null,"abstract":"Magnon transport through a magnetic insulator can be controlled by current-biased heavy-metal gates that modulate the magnon conductivity via the magnon density. Here, we report nonlinear modulation effects in 10$,$nm thick yttrium iron garnet (YIG) films. The modulation efficiency is larger than 40%/mA. The spin transport signal at high DC current density (2.2$times 10^{11},$A/m$^{2}$) saturates for a 400$,$nm wide Pt gate, which indicates that even at high current levels a magnetic instability cannot be reached in spite of the high magnetic quality of the films.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75031185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 6
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