Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session B42: Topological Bands and Nonlinearity |
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Sponsoring Units: DMP Chair: Wonhee Ko, University of Tennessee, Knoxville Room: Room 318 |
Monday, March 6, 2023 11:30AM - 11:42AM |
B42.00001: Electronic transport studies of ultrathin bismuth grown inside van der Waals materials Laisi Chen, Amy X Wu, Naol Tulu, Joshua Wang, Adrian Juanson, Kenji Watanabe, Takashi Taniguchi, Yinong Zhou, Chaitanya A Gadre, Marshall A Campbell, Luis A Jauregui, Xiaoqing Pan, Ruqian Wu, Javier Sanchez-Yamagishi Bismuth exhibits a wide variety of topological electronic phenomena depending on its dimensionality. 3D bismuth sits at a transition between different topological phases, while 2D bismuth is predicted to be a room temperature 2D topological insulator. Studies of 2D and ultrathin bismuth are limited by irregular surfaces and substrate interactions in MBE. We present a new synthesis approach where ultrathin bismuth crystals are molded from the melt phase inside vdW materials under compression. This method consistently produces 5-30 nm thick bismuth crystals with atomically flat surfaces and single crystal domains up to 10 um in size. Cryogenic transport studies of the vdW-molded ultrathin bismuth exhibit metallic temperature dependence, as a result of the SOC-induced surface states conducting in parallel with the gapped bulk bands due to confinement effect. The residual resistance ratio is 10x larger than epitaxial-grown bismuth of similar thicknesses. Furthermore, magnetotransport shows gate-tunable quantum oscillations originating from the multi-pocket surface states. In my talk, I will present up-to-date transport data analysis including thickness-dependence and field effects on various ultrathin bismuth devices. We anticipate that the vdW-molding technique will be generalized for other soft materials and our research can cast new light on ultrathin bismuth studies. |
Monday, March 6, 2023 11:42AM - 11:54AM |
B42.00002: Solitons and topology: Observation of cnoidal wave localization in non-linear topolectric circuits Hendrik Hohmann, Tobias Hofmann, Tobias Helbig, Lavi K Upreti, Alexander Stegmaier, Alexander Fritzsche, Tobias Müller, Ching Hua Lee, Martin Greiter, Ronny Thomale Topological phases have been realized in a variety of classical metamaterials. They provide easily accessible platforms to study topology in regimes beyond experimental limitations of real materials. While most implementations are limited to the linear regime, investigating non-linear effects promises to reveal a plethora of new phenomena, such as solitons and chaos. To study the intertwining of topology and non-linearity we engineered a topolectric circuit reminiscent of the Su-Schrieffer-Heeger (SSH) model with added tunable onsite non-linearity. We observe the localized cnoidal (LCn) state which maintains the spatial exponential localization of the SSH edge mode while distorting a sinusoidal input into eccentric waves in time domain. In this talk, we complement the non-linear differential equations with the theory of topological localization and develop an analytic description of the LCn state. |
Monday, March 6, 2023 11:54AM - 12:06PM |
B42.00003: Emergence of the non-Hermitian topology in generalized eigenvalue problems with Hermitian matrices Takuma Isobe, Tsuneya Yoshida, Yasuhiro Hatsugai Topological band theory has been studied as one of the central issues of condensed matter physics in these fifteen years. It has been initiated as the eigenvalue problems of a Hermitian matrix [1,2], which has revealed many non-trivial phenomena such as bulk-boundary correspondence [3]. Notably, recent studies have extended the framework of the topological band theory to the non-Hermitian eigenvalue problems [4,5,6]. This extension reveals the existence of the topological phenomena unique to the non-Hermitian systems. |
Monday, March 6, 2023 12:06PM - 12:18PM |
B42.00004: Distributed topological zero modes in a Non Hermitian quantum system Lea Sirota, Sayan Jana Non-Hermitian systems have emerged recently due to their unique properties, like |
Monday, March 6, 2023 12:18PM - 12:30PM |
B42.00005: Discrete Quantum Geometry for Nonlinear Optical Responses David C Jones For the two past decades, topology has become the centerpiece of many fields in condensed matter physics. In particular, k-space topology has led to many discoveries including topological insulators, Chern insulators, Weyl semimetals, and topological superconductors. These systems are predicted to exhibit unique electronic transport responses described by topological invariants evaluated through an integral of the Berry curvature among occupied states within the Fermi sea. Numerically, these calculations can prove challenging as certain electronic band features, such as band crossings, can lead to singularities, especially when close to the Fermi surface. An alternative approach however is to describe the responses using geometric properties of the Fermi surface. For example, by constructing a 3-dimensional discrete quantum manifold of the Fermi surface, it has recently been demonstrated that the intrinsic Hall conductivity resolved in spin can be precisely computed [1]. |
Monday, March 6, 2023 12:30PM - 12:42PM |
B42.00006: The effect of disorder and nonlinearity on topological slow light Jonas F Karcher, Sarang Gopalakrishnan, Mikael C Rechtsman In photonic crystal waveguides, light can be significantly slowed at wavelengths near the Brillouin zone edge, where the group velocity approaches zero. This has the effect of making light interact more strongly with matter, potentially leading to significant enhancement of nonlinear processes such as frequency comb generation and entangled pair creation. |
Monday, March 6, 2023 12:42PM - 12:54PM |
B42.00007: Local structural study of MoTe2 using atomic pair distribution function and EXAFS techniques Sumit Khadka, Milinda Abeykoon, Yu-Cheng Shao, Leighanne C. Gallington, Byron Freelon Below 250K, average scattering techniques have shown that 1T’ MoTe2 undergoes a first order structural phase transition (SPT) to a non-centrosymmetric orthorhombic, Td phase with emergence of Weyl points protected by broken inversion symmetry. However, due to the similarity of structures of these distinct phases and a small energy barrier between them, various distortions are observed at macroscopic as well as atomic scales. We present the local structure study of 1T’ MoTe2 over various temperatures ranging from 95K to room temperature by using scattering techniques more suited to the study local structures. We observed that on lowering the temperature interlayer atomic distances change significantly however the intralayer distances do not. This has been investigated using both small box and large box modelling approaches. From large box modelling analysis, we show effects of stacking faults and rotation of layers on the interlayer atomic distances which are consistent with the experimental observation.Understanding the interlayer behavior on MoTe2 through local structure studies can help to clarify some of the outstanding questions on the SPT and its effects on the emergence of the Weyl points at low temperatures. |
Monday, March 6, 2023 12:54PM - 1:06PM |
B42.00008: Supercurrent-induced topological phase transitions Kazuaki Takasan, Shuntaro Sumita, Youichi Yanase We will present our recent results showing that finite current in superconductors can induce topological phase transitions, as a result of the deformation of the quasiparticle spectrum by a finite center-of-mass (COM) momentum of the Cooper pairs [1]. To show the wide applicability of this mechanism, we examine the topological properties of three prototypical systems, the Kitaev chain, s-wave superconductors, and d-wave superconductors. We introduce a finite COM momentum as an external field corresponding to supercurrent and show that all the models exhibit current-induced topological phase transitions. We will also address the possibility of observing the phase transitions in experiments and the relation to the other finite COM momentum pairing states. If time allows, we would like to mention our more recent works [2] and ongoing studies. |
Monday, March 6, 2023 1:06PM - 1:18PM |
B42.00009: Topology of the Fermi sea: ordinary metals as topological materials Pok Man Tam, Martin Claassen, Charles L Kane It has long been known that the quantum ground state of a metal is characterized by an abstract manifold in momentum space called the Fermi sea. Fermi sea can be distinguished topologically in much the same way that a ball can be distinguished from a donut by counting the number of holes. The associated topological number, i.e. the Euler characteristic (χF), serves to classify metals. Here I will survey three recent proposals that relate χF to experimental observables, which are: (i) nonlinear responses [1], (ii) equal-time density correlations [2], and (iii) Andreev state transport along a Josephson pi-junction [3]. Moreover, from the quantum information perspective, we show that multipartite entanglement in real space probes the Fermi sea topology in momentum space [2]. This series of works provide a new perspective to study topology and universality in gapless quantum matters. |
Monday, March 6, 2023 1:18PM - 1:30PM |
B42.00010: Bistable Design in Topological Mechanical Metamaterials Haning Xiu, Harry Liu, Andrea Poli, Kai Sun, Guangchao Wan, Ellen Arruda, Xiaoming Mao, Zi Chen Quantum topological states of matter have been extensively used for studying novel mechanical metamaterials with topologically protected properties. Mechanical metamaterials exhibit exotic properties governed by structures rather than constituents. Maxwell lattices represent a class of topological mechanical metamaterials (TMMs) that exhibit floppy modes localized on the soft edge when they are topologically polarized. Achieving topological transformation in these materials can enable on-and-off switching of hard and soft edge states, providing new paths of exploring programmable mechanical response and wave propagation. However, it is desirable yet extremely challenging to control the topological polarization transition of a Maxwell lattice. Here a Maxwell lattice with bistable units is designed to implement synchronized transitions. These bistable units in the lattice exhibit two stationary configurations, at the topologically polarized and non-polarized phases, respectively. Remarkably, the bistable units allow the lattice to be conveniently and swiftly switched between the polarized and non-polarized phases. And we demonstrate dramatically different stiffnesses at the opposite surfaces in the topologically polarized phase both theoretically and experimentally. This new design will help provide novel TMMs with potential applications on stiffness tuning, impact mitigation, mechanological and neuromorphic computation, and flexible robotics. |
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