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Anomalous shift in Andreev reflection from side incidence

Physical Review B 2024年第23期110卷 235114-235114页

作者： Runze Li Chaoxi Cui Ying Liu Zhi-Ming Yu Shengyuan A. Yang Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China School of Materials Science and Engineering Hebei University of Technology Tianjin 300130 China Research Laboratory for Quantum Materials IAPME Faculty of Science and Technology University of Macau Macau SAR

Andreev reflection at a normal-superconductor interface may be accompanied with an anomalous spatial shift. The studies so far are limited to the top incidence configuration. Here, we investigate this effect in the side incidence configuration, with the interface parallel to the principal axis of superconductor. We find that the shift exhibits rich behaviors reflecting the character of pair potential. It has two contributions: one from the k-dependent phase of pair potential, and the other from the evanescent mode. For chiral p-wave pairing, the pairing phase contribution is proportional to the chirality of pairing and is independent of excitation energy, whereas the evanescent mode contribution is independent of chirality and is nonzero only for excitation energy below the gap. The two contributions also have opposite parity with respect to the incident angle. For dx2−y2-wave pairing, only the evanescent mode contribution exists, and the shift exhibits suppressed zones in incident angles, manifesting the superconducting nodes. The dependence of the shift on other factors, such as the angle of incident plane and Fermi surface anisotropy, are discussed.

关键词： Andreev reflection Transport phenomena Junctions Unconventional superconductors Bogoliubov-de Gennes equations

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Landau level spectrum and magneto-optical conductivity in tilted Weyl semimetal

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Physical Review B 2023年第8期107卷 085146-085146页

作者： Pu Liu Chaoxi Cui Xiao-Ping Li Zhi-Ming Yu Yugui Yao Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China School of Physical Science and Technology Inner Mongolia University Hohhot 010021 China

We present a systematic investigation of the magnetoresponses of the Weyl points (WPs) with a topological charge of n=2,3, and 4, and with both linear and quadratic energy tilt. The linear tilt always tends to squeeze the Landau levels (LLs) of both conduction and valence bands of all the WPs, and eventually leads to LL collapse in the type-II phase. However, the quadratic energy tilt has more complex influences on the LLs of the unconventional WPs. For charge-n (n=2,4) WP, the influence of the quadratic tilt on the LLs of conduction and valence bands are opposite, i.e., if the LLs of conduction (valence) bands are squeezed, then that of the valence (conduction) bands are broadened and the squeezed LL spectrum will be collapsed in the type-III phase. But, the LL collapse generally cannot be found in the type-III charge-3 WP. Moreover, for charge-n (n=2,3) WP, the quadratic tilt breaks the degeneracy of the chiral LLs regardless of the direction of the magnetic field, leading to additional optical transitions and magneto-optical conductivity peaks at low frequencies. Interestingly, the four chiral LLs in charge-4 WP are always not degenerate. Hence there inevitably exist magneto-optical conductivity peaks at low frequencies for charge-4 WP. Since the density of state of the LL spectrum is very large, one can expect that the low-frequency magneto-optical responses in unconventional WPs would be significant and may be used for developing efficient terahertz photodetectors.

关键词： Landau levels Magneto-optics Optical conductivity Topological materials Weyl semimetal Linear response theory k dot p method

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Geometric mean of bipartite concurrences as a genuine multipartite entanglement measure

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Physical Review Research 2022年第2期4卷 023059-023059页

作者： Yinfei Li Jiangwei Shang Key Lab. of Advanced Optoelectronic Quantum Architecture and Measurement of Ministry of Education School of Physics Beijing Institute of Technology Beijing 100081 China

In this paper, we propose the geometric mean of bipartite concurrences as a genuine multipartite entanglement measure. This measure achieves the maximum value for absolutely maximally entangled states and has desirable properties for quantifying potential quantum resources. The simplicity and symmetry in the definition facilitates its computation for various multipartite entangled states including the GHZ states and the W states. With explicit examples, we show that our measure results in distinct entanglement orderings from other measures and can detect differences in certain types of genuine multipartite entanglement while other measures cannot. These results justify the potential application of our measure for tasks involving genuine multipartite entanglement.

关键词： Entanglement measures Nonlocality quantum entanglement quantum foundations

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A Spiral Graphene Framework Containing Highly Ordered Graphene Microtubes for Polymer Composites with Superior Through-Plane Thermal Conductivity

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Chinese Journal of Chemistry 2022年第3期40卷 329-336页

作者： Jinrui Gong Xue Tan Qilong Yuan Zhiduo Liu Junfeng Ying Le Lv Qingwei Yan Wubo Chu Chen Xue Jinhong Yu Kazuhito Nishimura Nan Jiang Cheng-Te Lin Wen Dai Key Laboratory of Marine Materials and Related Technologies Zhejiang Key Laboratory of Marine Materials and Protective TechnologiesNingbo Institute of Materials Technology and Engineering(NIMTE)Chinese Academy of SciencesNingboZhejiang 315201China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBejjing 100049China Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement(MOE)Beijing Key Lab of Nonophotonics&Ultrafine Optoelectronic SystemsSchool of PhysicsBeijing Institute of TechnologyBeijing 100081China College of Materials Science and Engineering Hunan UniversityChangshaHunan 410082China Advanced Nano-processing Engineering Lob Mechanical Systems EngineeringKogakuin UniversityTokyo 192-0015Japan

As the power density of electronic devices increases,there has been an urgent demand to develop highly conductive polymer composites to address the accompanying thermal management *** to the ultra-high intrinsic thermal conductivity,graphene is considered a very promising filler to improve the thermal conductivity of ***,graphene-based polymer composites prepared by the conventional mixing method generally have limited thermal conductivity,even under high graphene loading,due to the failure to construct efficient heat transfer pathways in the polymer ***,a spiral graphene framework(SGF)containing continuous and highly ordered graphene microtubes was developed based on a modified CVD *** embedding into the epoxy(EP)matrix,the graphene microtubes can act as efficient heat pathways,endowing the SGF/EP composites with a high through-plane thermal conductivity of 1.35 W·m^(-1)·K^(-1) at an ultralow graphene loading of 0.86 wt%.This result gives a thermal conductivity enhancement per 1 wt%filler loading of 710%,significantly outperforming various graphene structures as *** addition,we demonstrated the practical application of the SGF/EP composite as a thermal interface material for efficient thermal man-agement of the light-emitting diode(LED).

关键词： Graphene Chemical vapor deposition Polymer Thermal conductivity Thermal management material

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Estimating many properties of a quantum state via quantum reservoir processing

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Physical Review Research 2024年第1期6卷 013211-013211页

作者： Yinfei Li Sanjib Ghosh Jiangwei Shang Qihua Xiong Xiangdong Zhang Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement of Ministry of Education School of Physics Beijing Institute of Technology Beijing 100081 China Beijing Academy of Quantum Information Sciences Beijing 100193 China State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics Tsinghua University Beijing 100084 China

Estimating properties of a quantum state is an indispensable task in various applications of quantum information processing. To predict properties in the postprocessing stage, it is inherent to first perceive the quantum state with a measurement protocol and store the information acquired. In this paper, we propose a general framework for constructing classical approximations of arbitrary quantum states with quantum reservoirs. A key advantage of our method is that only a single local measurement setting is required for estimating arbitrary properties, while most of the previous methods need an exponentially increasing number of measurement settings. To estimate M properties simultaneously, the size of the classical approximation scales as lnM. Moreover, this estimation scheme is extendable to higher-dimensional systems and hybrid systems with nonidentical local dimensions, which makes it exceptionally generic. We support our theoretical findings with extensive numerical simulations.

关键词： quantum information theory quantum parameter estimation quantum tomography

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First-principles perspective on full-spectrum infrared photodetectors from doping an excitonic insulator

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Physical Review B 2022年第3期106卷 035135-035135页

作者： Jing Liu Yuanchang Li Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) Beijing 100081 China Advanced Research Institute of Multidisciplinary Science Beijing Institute of Technology Beijing 100081 China

Innovations in imaging technology involve finding strategies and materials suitable for detection applications over the entire infrared range. Herein, we propose a new design concept based on the unique feature of an excitonic insulator, namely, negative exciton transition energy (Et). We demonstrate this concept using first-principles GW-Bethe-Salpeter equation calculations on one-dimensional organometallic wire (CrBz)∞. The pristine (CrBz)∞ exhibits an excitonic instability due to a negative Et for the lowest exciton. Substitutional doping can continuously tune the Et from ∼0 to ∼0.6 eV, which shows the ability of photon detection from terahertz to near infrared. This type of detector has advantages of outstanding wavelength selectivity, reduced thermal disturbance, and elevated working temperature. Our paper not only adds another member in the family of rare one-dimensional excitonic insulators, but also opens a new avenue for the development of high-performance infrared photodetectors in the future.

关键词： Excitons Nanowires Bethe-Salpeter equation First-principles calculations

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Bulk Fermi arc transition induced large photogalvanic effect in Weyl semimetals

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Physical Review B 2022年第12期106卷 125416-125416页

作者： Jin Cao Maoyuan Wang Zhi-Ming Yu Yugui Yao Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China

The surface Fermi arc, as a hallmark of Weyl semimetals (WSMs), has been well known in current research, but it remains a challenge to unveil novel phenomena associated with the Fermi arc. Here, in WSMs, namely, the photoinduced transition between the bulk states and the Fermi arc. We find this process is significant and can lead to a large effective three-dimensional shift current on the boundaries with the Fermi arc in wide terahertz range. Moreover, due to the low symmetry of the boundaries, the surface photogalvanic effect predicted here can appear in a large class of WSMs that can not have bulk shift current. Hence, our work not only unveils a hidden photogalvanic effect in WSMs but also suggests that all the WSMs are promising material candidates for developing efficient terahertz photodetectors.

关键词： Fermi surface Photogalvanic effect Semimetals Weyl semimetal

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Cn-symmetric higher-order topological crystalline insulators in atomically thin transition metal dichalcogenides

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Physical Review B 2022年第4期105卷 045417-045417页

作者： Shifeng Qian Gui-Bin Liu Cheng-Cheng Liu Yugui Yao Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China and Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China

Based on first-principles calculations and symmetry analysis, we predict atomically thin (1−N layers) 2H group-VIB transition metal dichalcogenides (TMDs) MX2 (M = Mo, W; X = S, Se, Te) are large-gap higher-order topological crystalline insulators (HOTCIs) protected by C3 rotation symmetry. We explicitly demonstrate the nontrivial topological indices and the existence of hallmark corner states with quantized fractional charge for these familiar TMDs with a large bulk optical band gap (1.64–1.95eV for the monolayers), which would facilitate the experimental verification and exploration of the HOTCI states. Furthermore, we find that the well-defined corner states exist in the triangular finite-size flakes with armchair edges of the atomically thin (1−N layers) 2H group-VIB TMDs, and the corresponding quantized fractional charge is the number of layers N modulo three. The fractional corner charge will double when spin degree of freedom is taken into account.

关键词： First-principles calculations Symmetry protected topological states Topological materials Transition metal dichalcogenides Ultrathin films

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Harnessing Graphene Plasmons by Accessing the Retardation Regime

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ACS Applied Materials and Interfaces 2025年第22期17卷 32782-32789页

作者： Zhang, Jiasheng Xing, Qiaoxia Zhao, Tuoyu Wang, Shunjia Ma, Junwei Wang, Chong Wang, Jiajun Xie, Yuangang Huang, Shenyang Song, Chaoyu Wan, Quan Shi, Lei Tao, Zhensheng Shi, Wu Li, Xuesong Zhou, Lei Yan, Hugen State Key Laboratory of Surface Physics Key Laboratory of Micro- and Nano-Photonic Structures Ministry of Education Shanghai Key Laboratory of Metasurfaces for Light Manipulation Department of Physics Fudan University Shanghai 200433 China Inner Mongolia Key Laboratory of Microscale Physics and Atom Innovation School of Physical Science and Technology Inner Mongolia University Hohhot 010021 China State Key Laboratory of Surface Physics Institute for Nanoelectronic Devices and Quantum Computing Fudan University Shanghai 200433 China Zhangjiang Fudan International Innovation Center Fudan University Shanghai 201210 China Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China School of Integrated Circuit Science and Engineering Exemplary School of Microelectronics University of Electronic Science and Technology of China Chengdu 611731 China Shenzhen Institute for Advanced Study University of Electronic Science and Technology of China Shenzhen 518110 China

Plasmons in graphene are highly tunable, mainly by leveraging the carrier density and Drude scattering. Here, we introduce another scheme, i.e., accessing the retardation regime (originated from the finite speed of light), to engineer the lifetime and dispersion of plasmons in graphene in the terahertz regime. We find that the retardation regime can be approached by reducing plasmon momentum in artificially stacked multilayer graphene systems with large Drude weight, and this can significantly increase the plasmon lifetime. In addition, an explicit theoretical model along with finite-element simulation was given, consistent with the experimental findings. Our work opens another avenue to manipulate terahertz plasmons in graphene. © 2025 American Chemical Society.

关键词： Drude weight graphene plasmon retardation effects terahertz

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Multiple topological phases in tetradymite compounds M2Te2P(M=Ti,Zr, or Hf)

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Physical Review B 2024年第22期109卷 L220102-L220102页

作者： M. J. Pan B.-X. Li H. Wang J. D. Liu F. M. Chen J. R. Huang G. X. Qu S. Y. Gao B. Jiang Y.-B. Huang X. Shi T.-L. Xia H. M. Weng T. Qian Beijing National Laboratory for Condensed Matter Physics and Beijing 100049 China Department of Physics Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices Shanghai Advanced Research Institute Chinese Academy of Sciences Shanghai 201204 China Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education) Laboratory for Neutron Scattering Dongguan 523808 China

Since the advent of time-reversal-invariant topological insulators, the generalization of topology concepts has led to the discovery of a wide range of topological states. These topological states may undergo topological phase transitions (TPTs) accompanied by discontinuous changes in topological invariants. In this Letter, by combining time- and angle-resolved photoemission spectroscopy measurements with first-principles calculations, we have demonstrated the existence of distinct TPTs in the unoccupied states above the Fermi level in the M2Te2P (M=Ti, Zr, or Hf) family. These TPTs arise from the inversion of the transition metal d and Te p orbitals due to the enhancement of spin-orbit coupling and variation in crystal fields, as the transition metal changes from 3d to 4d and then to 5d. Eventually, dual topological states are achieved in the 5d system Hf2Te2P, where a type-III Dirac semimetal state coexists with a strong topological insulator state. Finally, we reveal a rapid relaxation process in the nonequilibrium population of the Dirac surface state due to the presence of an additional interband scattering channel in the bulk.

关键词： Electrical properties of membranes Electronic structure Electronic structure of atoms & molecules Fermi surface First-principles calculations Spin-orbit coupling Surface states Topological materials

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