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I am a researcher at Hefei National Labotory and ICQD, the University of Science and Technology of China (USTC). My research field is theoretical condensed matter physics, focusing on novel quantum states of matter (e.g., topological insulators/semimetals, quantum Hall effects, and unconventional superconductivity), their unique quantum transport properties and potential functionality/applications. I also work on non-Hermitian (topological) physics.

Research interests and highlights

1. Unconventional antiferromagnets.

1-1) We show that proximity-induced Cooper pairs in altermagnets acquire finite momentum, despite zero net magnetization, leading to exotic phenomena such as periodic oscillations in the pairing correlation, 0-π transitions in Josephson junctions, large oblique dominant transfer trajectories of Cooper pairs, and anomalous Fraunhofer pattern. [Nature Commun. 2024]

1-2) We propose employing the Coulomb drag to probe altermagnetism. We find that transverse currents can be dragged in the passive layer, leading to Hall drag effects even without spin-orbit coupling. All the drag effects of altermagnets have unique angle dependence, which can be measured in a multi-terminal setup to serve as signatures for altermagnetism. [arXiv:2412:13927] 

2. Topological phenomena in non-Hermitian systems.

2-1) We study the Hatano-Nelson model in presence of repulsive nearest-neighbor interactions. At half-filling, we find two 𝒫𝒯 phase transitions, as interaction strength increases. Away from half-filling, the many-body spectrum shows nontrivial point gaps, indicating the skin effect of extensive many-body eigenstates under open boundaries. [PRB 2022] We extend our theory to spinful systems and propose the non-Hermitian Mott skin effect. [PRL 2024]

2-2) We show that the second-order skin effect is robust and can be enhanced by magnetic fields. [PRL 2023, Editors' Suggestions] Our theory has been applied to experiments. [e.g., APL 2024]

3. Topological states of matter and their unique transport 

3-1) We propose a 2D shifted CDW phase and show that it possesses topological properties that give rise to edge modes, exhibiting duality to the chiral edge modes of Chern insulators. [PRL 2023]. We work with experimental collaborators to implement our theory in Ta₂Se₈I [Nature Physics 2024]. 

3-2) We find the super-resonant transport of Dirac surface states and its resulting quantum oscillations under in-plane magnetic fields. [PRL 2021] Our theory has been applied to the HgTe experiment [NL 2023]. 

3-3) We develop a scattering approach to study QH/superconductor/QH junctions based on 2D Dirac semimetals and propose two setups where CAR can reach unity probability. [PRL 2019] 

3-4) We derive analytically the topological invariant of QSHIs under perpendicular magnetic fields and show that QSHIs in HgTe and InAs/GaSb quantum wells can sustain large magnetic fields. [PRB 2014] We reveal that in these quantum wells, the Dirac point of edge states is pulled to be close to and even buried in the bulk valence bands when the system is in a deeply inverted regime. [PRB 2018] Our results provide plausible explanations for the experimental observations on the robust quantum edge transport of QSHIs subjected to strong magnetic fields.

3-5) We present exact solutions of the edge states of Landau levels in topological insulator thin films with open boundary conditions, and provide an intuitive edge-state picture to fully understand QH and QSH effects of the surface electrons. [SR 2015]. Our theory has been implemented in experiments [e.g., PRL 2023]. 

4. Higher-Order Topological States of Matter

4-1) Quantum computation based on second-order topological superconductors (SOTSs). We propose a generic model for SOTSs and demonstrate the exotic features of Majorana zero modes (Majoranas). We construct the fundamental fusion principles of the Majoranas, conceive different setups and present concrete protocols to exchange and fuse the Majoranas for non-Abelian braiding and holonomic quantum gate operations. [PRR 2020] We put forward a feasible scheme to realize networks that allow to nucleate and braid Majoranas in an all-electrical manner without fine-tuning.  [PRB 2020]

4-2) Detections and functionalities. We propose 0-π Josephson transitions as novel experimental signatures to detect 2D SOTSs and identify the SOTS-based Josephson junction as a fully electric platform to nucleate or annihilate Majorana bound states. [PRR 2020] We find that higher-order Weyl superconductors can be realized in odd-parity topological superconductors by periodic driving. [PRB 2021] We propose an intrinsic 3D Fabry-Perot type interferometer that offers feasible transport signatures to detect SOTIs. [PRL 2022, Cover paper]. Our theory have been applied to the Bi4Br4 experiment by Hasan's group at Princeton [Nature physics 2024].   

4-3) Disorder problem. Random flux is commonly believed to be incapable of driving full metal-insulator transitions. Surprisingly, we show that random flux can after all induce a full metal-insulator transition in the 2D Su-Schrieffer-Heeger model. The resulting insulating phase can even be a higher-order topological insulator. [PRB 2022, Editor's Suggestions]

5. Transport Properties of Weyl and Dirac Semimetals

5-1) Magnetotransport and the chiral anomaly. We develop a comprehensive magnetotransport theory of Weyl semimetals (WSM) in the strong field limit. [PRB 2015, NJP 2016] Our theory has been extensively applied to experiments [e.g., NC 2016, SA 2022]. We provide a systematic study of magnetic oscillations of acoustic phonons in WSM. [PRB 2020]. This theory has also been applied to experiments [e.g., NC 2022].

5-2) Transport in hybrid structures. We find that a chirality Josephson current emerges under Zeeman fields even without phase difference across the junction and embodies a novel quantum anomaly associated with a Z2 symmetry at low energies. [PRL 2018] In an extended regime, the zero-bias differential conductance of a time-reversal symmetric WSM/SC junction acquires the universal value of e²/h per channel. [PRB 2018]  In NSN junctions based on time-reversal broken WSM, a net spin polarization of Cooper pairs appear due an electron population imbalance between the two chirality. [PRB 2019]

近期论文（完整论文列表请见 谷歌学术）

[1] S.-B. Zhang#, L.-H. Hu#, & T. Neupert, Finite-momentum Cooper pairing in proximitized altermagnets, Nature Commun. 15, 1801 (2024).

[2] M. Litskevich*, M. Hossain*, S.-B. Zhang* et al., Boundary modes of a charge density wave state in a topological material, Nature Physics 20, 1254 (2024).

[3] M. Bahari, S.-B. Zhang, C. Li, S. Choi, P. Rüßmann, C. Timm, & B. Trauzettel, Helical topological superconducting pairing at finite excitation energies, Phys. Rev. Lett. 132, 266201 (2024).

[4] T. Yoshida, S.-B. Zhang, T. Neupert, & N. Kawakami, Non-Hermitian Mott skin effect, Phys. Rev. Lett. 132, 266201 (2024).

[5] C.-A. Li, B. Trauzettel, T. Neupert, & S.-B. Zhang#, Enhancement of second-order non-Hermitian skin effect by magnetic fields, Phys. Rev. Lett. 131, 116601 (2023) [Editors‘ Suggestion].

[6] S.-B. Zhang#, X. Liu, M. Hossain, J.-X. Yin, Z. Hasan, & T. Neupert#, Emergent edge modes in shifted quasi-one-dimensional charge density waves, Phys. Rev. Lett. 130, 106203 (2023).

[7] S.-B. Zhang#, C.-A. Li, F. Peña-Benitez, P. Surówka, R. Moessner, L. Molenkamp, & B. Trauzettel, Super-resonant transport of topological surface states subjected to in-plane magnetic fields, Phys. Rev. Lett. 127, 076601 (2021).

[8] C.-A. Li#, S.-B. Zhang#, J. Li, & B. Trauzettel, Higher-order Fabry-Pérot interferometer from topological hinge states, Phys. Rev. Lett. 127, 026803 (2021) [Cover Article].

[9] S.-B. Zhang and B. Trauzettel, Perfect crossed Andreev reflection in Dirac hybrid junctions in the quantum Hall regime, Phys. Rev. Lett. 122, 257701 (2019).

[10] S.-B. Zhang, J. Erdmenger, and B. Trauzettel, Chirality Josephson current due to a novel quantum anomaly in inversion-asymmetric Weyl semimetals, Phys. Rev. Lett. 121, 226604 (2018).

• -- 量子输运及相关凝聚态理论
• -- 表面和界面的拓扑电子学
• -- 开放和非平衡量子系统
• -- 拓扑超导量子计算

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