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Double Dirac nodal line semimetal with a torus surface state

Physical Review B 2021年第16期103卷 L161109-L161109页

作者： Xiao-Ping Li Botao Fu Da-Shuai Ma Chaoxi Cui Zhi-Ming Yu Yugui Yao Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) Beijing Key Laboratory of Nanophotonics & Ultrafine Optoelectronic Systems and School of Physics Beijing Institute of Technology Beijing 100081 China College of Physics and Electronic Engineering Center for Computational Sciences Sichuan Normal University Chengdu 610068 China

We propose a class of nodal line semimetals that host an eightfold-degenerate double Dirac nodal line (DDNL) with negligible spin-orbit coupling. We find only 5 of the 230 space groups host the DDNL. The DDNL can be considered as a combination of two Dirac nodal lines, and has a trivial Berry phase. This leads to two possible but completely different surface states, namely, a torus surface state covering the whole surface Brillouin zone and no surface state at all. Based on first-principles calculations, we predict that the hydrogen storage material LiBH is an ideal DDNL semimetal, where the line resides at Fermi level, is relatively flat in energy, and exhibits a large linear energy range. Interestingly, both the two novel surface states of DDNL can be realized in LiBH. Further, we predict that with a magnetic field parallel to DDNL, the Landau levels of DDNL are doubly degenerate due to a Kramers-like degeneracy and have a doubly degenerate zero mode.

关键词： Fermi surface Surface states Topological phases of matter

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Electro-optic modulation of solution-processed molybdenum disulfide

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Physical Review Applied 2024年第3期22卷 034057页

作者： Songwei Liu Yingyi Wen Jingfang Pei Xiaoyue Fan Yongheng Zhou Yang Liu Ling-Kiu Ng Yue Lin Teng Ma Panpan Zhang Xiaolong Chen Gang Wang Guohua Hu Department of Electronic Engineering Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Department of Electrical and Electronic Engineering Shun Hing Institute of Advanced Engineering CAS Key Laboratory of Design and Assembly of Functional Nanostructures and State Key Laboratory of Structural Chemistry Department of Applied Physics State Key Laboratory of Information Photonics and Optical Communications

Solution-processed molybdenum disulfide (MoS2) shows promise for tunable photonics and optoelectronics development. However, though scalable, it often leads to devices with inferior performance as a result of its random, discrete nature. In this study, we show via density-functional-theory calculations that the electronic structure of the individual solution-processed nanosheets can be modulated collectively by external electric fields. Particularly, the nanosheets can form Stark ladders, giving variations in the underlying optical processes and thus tunable collective optical properties. We confirm this electro-optical modulation experimentally using solution-processed MoS2 films with ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)] incorporated, and prove that the local polarization fields from P(VDF-TrFE) can modulate the collective optical properties of the MoS2, specifically, the optical absorption and photoluminescence. Given the scalability of solution processing, our results underpin the potential of electro-optical modulation of solution-processed MoS2 for tunable photonics and optoelectronics development. To illustrate this potential, we demonstrate solution-processed electroabsorption modulators.

关键词： Electric field effects Electro-optic effects optoelectronics Photonics 2-dimensional systems Layered semiconductors Transition metal dichalcogenides Chemical solution deposition

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Optical signature for distinguishing between Mott-Hubbard, intermediate, and charge-transfer insulators

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Physical Review B 2022年第24期106卷 L241101-L241101页

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

Determining the nature of band gaps in transition-metal compounds remains challenging. We present a first-principles study on electronic and optical properties of CoO using hybrid functional pseudopotentials. We show that optical absorption spectrum can provide a clear fingerprint to distinguish between Mott-Hubbard, intermediate, and charge-transfer insulators. This discrimination is reflected by the qualitative difference in peak satellites due to unique interplay between d−d and p−d excitations, thus allowing identification from experimental data alone, unlike the existing methods that require additional theoretical interpretation. We conclude that the CoO is an intermediate rather than a Mott-Hubbard insulator as is initially believed.

关键词： Band gap Electronic structure Strongly correlated systems Density functional calculations First-principles calculations

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Multipartite entanglement measures: A review

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Fundamental Research 2024年

作者： Ma, Mengru Li, Yinfei Shang, Jiangwei Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement of Ministry of Education School of Physics Beijing Institute of Technology Beijing 100081 China

quantum entanglement, a fundamental aspect of quantum mechanics, has captured significant attention in the era of quantum information science. In multipartite quantum systems, entanglement plays a crucial role in facilitating various quantum information processing tasks, such as quantum teleportation and dense coding. In this article, we review the theory of multipartite entanglement measures, with a particular focus on the genuine as well as the operational meaning of multipartite entanglement measures. By providing a thorough and valuable insight on this field, we hope that this review would inspire and guide researchers in their endeavors to further develop novel approaches for characterizing multipartite entanglement. © 2024 The Authors

关键词： Entanglement measures Multipartite entanglement quantum entanglement quantum information

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Multipartite entanglement measures: a review

arXiv

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arXiv 2023年

关键词： quantum entanglement

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Reliable optimization of arbitrary functions over quantum measurements

arXiv

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arXiv 2023年

作者： Luo, Jing Shang, Jiangwei Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement of Ministry of Education School of Physics Beijing Institute of Technology Beijing100081 China

As the connection between classical and quantum worlds, quantum measurements play a unique role in the era of quantum information processing. Given an arbitrary function of quantum measurements, how to obtain its optimal value is often considered as a basic yet important problem in various applications. Typical examples include but not limited to optimizing the likelihood functions in quantum measurement tomography, searching the Bell parameters in Bell-test experiments, and calculating the capacities of quantum channels. In this work, we propose reliable algorithms for optimizing arbitrary functions over the space of quantum measurements by combining the so-called Gilbert’s algorithm for convex optimization with certain gradient algorithms. With extensive applications, we demonstrate the efficacy of our algorithms with both convex and nonconvex functions. © 2023, CC BY.

关键词： Convex optimization

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Eco-friendly non-acid intercalation and exfoliation of graphite to graphene nanosheets in the binary-peroxidant system for EMI shielding

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Chinese Chemical Letters 2021年第11期32卷 3469-3473页

作者： Ping Wang Bin Guo Zhi Zhang Weinan Gao Wei Zhou Huaxin Ma Wenyu Wu Junfeng Han Ruijun Zhang State Key Laboratory of Metastable Materials Science and Technology Yanshan UniversityQinhuangdao 066004China Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement Ministry of EducationSchool of PhysicsBeijing Institute of TechnologyBeijing 100081China

The development of the preparation strategy for high-quality and large-size graphene via eco-friendly routes is still a challenging ***,we have successfully developed a novel route to chemically exfoliate natural graphite into high-quality and large-size graphene in a binary-peroxidant *** system is composed of urea peroxide(CO(NH_(2))_(2)·H_(2)O_(2))and hydrogen peroxide(H_(2)O_(2)),where CO(NH_(2))_(2)·H_(2)O_(2)is used in preparing graphene for the first *** from the complete decomposition of CO(NH_(2))_(2)·H_(2)O_(2)and H_(2)O_(2)into gaseous species under microwave(MW)irradiation,no water-washing and effluent-treatment are needed in this chemical exfoliation procedure,thus the preparation of graphene in an eco-friendly way is *** resultant graphene behaves a large-size,high-quality and few-layer feature with a yield of~100%.Then 4µm-thick ultrathin graphene paper fabricated from the as-exfoliated graphene is used as an electromagnetic interference(EMI)shielding *** its absolute effectiveness of EMI shielding(SSE/t)is up to 34,176.9 dB cm^(2)/g,which is,to the best of our knowledge,among the highest values so far reported for typical EMI shielding *** EMI shielding performance demonstrates a great application potential of graphene paper in meeting the ever-increasingly EMI shielding demands in miniaturized electronic devices.

关键词： Graphene exfoliation Eco-friendly Graphene paper EMI shielding

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Colossal layer Nernst effect in twisted moiré layers

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Physical Review B 2024年第20期109卷 L201403-L201403页

作者： Jin-Xin Hu Chuanchang Zeng Yugui Yao Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore Beijing Academy of Quantum Information Sciences Beijing 100193 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

In this work, we establish a theoretical analysis of the emergence of layer-contrasted Nernst response perpendicular to the direction of the temperature gradient in twisted moiré layers, called layer Nernst effect (LNE). This phenomenon arises from the trigonal warping of the Fermi surface along with a layer-contrasted pseudomagnetic field. Interestingly, the Fermi surface's warping explicitly breaks intravalley inversion symmetry, which leads to an imbalance between left- and right-moving carriers, thus resulting in a nonvanishing LNE. We then validate our theoretical scheme by applying it to twisted bilayer graphene (TBG). Importantly, we find that the LNE coefficient in TBG can reach values as high as 103 A/(m·K), surpassing those of previously known materials by at least one order of magnitude. These results provide a theoretical foundation for utilizing TBG and other twisted moiré layers as promising platforms to explore layer caloritronics and develop thermoelectric devices.

关键词： Transport phenomena Twistronics Graphene Transition metal dichalcogenides Twisted heterostructures Boltzmann theory

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Exceptional point empowered near-field routing of hyperbolic polaritons

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Science Bulletin 2024年第22期69卷 3491-3495页

作者： Zhiwei Guo Jiayue Jiang Yuqian Wang Jose Alvarez-Cuervo Aitana Tarazaga Martin-Luengo Shengyu Hu Jie Jiang Pablo Alonso Gonzalez Jiahua Duan Hong Chen MOE Key Laboratory of Advanced Micro-Structured Materials School of Physics Science and EngineeringTongji UniversityShanghai 200092China Department of Physics University of OviedoOviedo 33003Spain Center of Research on Nanomaterials and Nanotechnology CINN(CSIC-Universidad de Oviedo)El Entrego 33003Spain Center for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement(MOE)School of PhysicsBeijing Institute of TechnologyBeijing 100081China Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic System Beijing Institute of TechnologyBeijing 100081China

Subwavelength-scale manipulation of electromagnetic waves forms the cornerstone of next-generation photonic devices and quantum information processing[1],where extensive efforts have focused on momentum-frequency dispersion through modification of the sizes,shape topology,and symmetry of the isofrequency contours(IFCs)[2,3].For instance,twisting of the multi-layers of stacked vdW materials results in a topological transition from open(hyperbolic-like)to closed(elliptical-like)IFCs(i.e.,control of the propagation wavefront).In contrast,the symmetry of IFCs,which is deeply rooted in the system symmetry,is more difficult to modulate[4].For example,hyperbolic polaritons exhibit four mirrorsymmetric beams in high-symmetry orthorhombic crystals,while asymmetric propagation of tilted hyperbolic shear polaritons only emerges in low-symmetry monoclinic crystals[3].

关键词： hyperbolic symmetry polar

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Anomalous shift in Andreev reflection from side incidence

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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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