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 Q29: Strongly Correlated Systems, Including Quantum Fluids and Solids XIII |
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Sponsoring Units: DCMP Chair: Marcelo Jaime, Los Alamos Natl Lab Room: Room 221 |
Wednesday, March 8, 2023 3:00PM - 3:12PM |
Q29.00001: Observation of Three-Dimensional Flat Bands and Dirac Cones in a Pyrochlore Superconductor Jianwei Huang, Chandan Setty, Liangzi Deng, Jing-Yang You, Hongxiong Liu, Sen Shao, Ji Seop Oh, Yucheng Guo, Yichen Zhang, Ziqin Yue, Jia-Xin Yin, Makoto Hashimoto, Donghui Lu, Sergey Gorovikov, Pengcheng Dai, Zahid M Hasan, Yuan-Ping Feng, Robert J Birgeneau, Youguo Shi, Paul C. W. W Chu, Guoqing Chang, Qimiao Si, Ming Yi Emergent phases often appear when the electronic kinetic energy is comparable to the Coulomb interactions. One approach to seek material systems as hosts of such emergent phases is to realize localization of electronic wavefunctions due to the geometric frustration inherent in the crystal structure, resulting in flat electronic bands. Recently, such efforts have found a wide range of exotic phases in the two-dimensional kagome lattice, including magnetic order, time-reversal symmetry breaking charge order, nematicity, and superconductivity. However, the interlayer coupling of the kagome layers disrupts the destructive interference needed to completely quench the kinetic energy. Here we experimentally demonstrate that an interwoven kagome network—a pyrochlore lattice—can host a three-dimensional localization of electron wavefunctions. In particular, through a combination of angle-resolved photoemission spectroscopy, fundamental lattice model and density functional theory calculations, we present the novel electronic structure of a pyrochlore superconductor, CeRu2. We find striking flat bands along all momentum directions. We further find three-dimensional gapless Dirac cones predicted originally by theory in the diamond lattice space group with nonsymmorphic symmetry. Our work establishes the pyrochlore structure as a promising lattice platform to realize and tune novel emergent phases intertwining topology and many-body interactions. |
Wednesday, March 8, 2023 3:12PM - 3:24PM |
Q29.00002: Magnetic field-induced chiral spin liquids on the twisted transition-metal dichalcogenide moiré system Yixuan Huang, Donna Sheng, Jian-Xin Zhu Recent studies on the twisted transition-metal dichalcogenide heterobilayers and homonbilayers have demonstrated a desired platform to simulate Hubbard model physics with wide tunability through the twisted angle. We focus on the heterobilayer where the SU(2) symmetry is retained in the valley (spin) space, and investigate the Mott insulating phase at half filling approximated by a two-dimensional triangular Heisenberg model subject to a magnetic field. Interestingly, for intermediate fields a chiral spin liquid phase is observed before the transition to the partially polarized phase, due to an effective three-spin chiral interaction that are induced by the magnetic field. We further characterize the topological nature of the chiral spin liquid as the ν = 1/2 SU(2)1 Laughlin type, and map out the quantum phase diagram for different twist angles. |
Wednesday, March 8, 2023 3:24PM - 3:36PM |
Q29.00003: Spontaneous orbital magnetization of the Wigner Crystal phase in Bernal bilayer graphene Sandeep Joy, Brian J Skinner, Leonid Levitov, Zhiyu Dong At low density and low temperature, long-ranged Coulomb interactions in a two-dimensional electron gas cause the electrons to crystallize into a solid-like phase called a Wigner crystal(WC). In Bernal bilayer graphene, a perpendicular displacement field facilitates the formation of a WC by effectively flattening the bottom of the conduction band and thereby reducing the electrons' kinetic energy. Crucially, at a large displacement field, the conduction band adopts a "Mexican hat" shape, and this shape permits localized electrons to have finite angular momentum states that are nearly degenerate in energy with the ground state. Here we show that when the displacement field is larger than a certain critical value, Berry curvature drives the WC phase to be an orbital magnet with one unit of orbital angular momentum per electron. We calculate the corresponding phase diagram of the WC state, and we estimate its melting temperature and compressibility. |
Wednesday, March 8, 2023 3:36PM - 3:48PM |
Q29.00004: Fractionalization and Topology in Amorphous Electronic Solids Sunghoon Kim, Adhip Agarwala, Debanjan Chowdhury Band-topology is traditionally analyzed in terms of gauge-invariant observables associated with crystalline Bloch wavefunctions. Recent work has demonstrated that many of the free fermion topological characteristics survive even in an amorphous setting. In this work, we extend these studies to incorporate the effect of strong repulsive interactions on the fate of topology and other correlation induced phenomena. Using a parton-based approach, we obtain the interacting phase diagram for an electronic two-orbital model with tunable topology in a two dimensional amorphous network. In addition to the (non-)topological phases that are adiabatically connected to the free fermion limit, we find a number of strongly interacting amorphous analogs of crystalline Mott insulating phases with non-trivial chiral neutral edge modes, and a fractionalized Anderson insulating phase. The amorphous networks thus provide a new playground for studying a plethora of exotic states of matter, and their glassy dynamics, due to the combined effects of non-trivial topology, disorder, and strong interactions. |
Wednesday, March 8, 2023 3:48PM - 4:00PM |
Q29.00005: Experimental determination of band structures of CeCoSi by an angle-resolved photoelectron spectroscopy Akio Kimura, Tomoki Yoshikawa, Yuto Fukushima, Takashi Kono, Munisa Nurmamat, Masashi Arita, Keisuke Mitsumoto, Hiroshi Tanida Strongly correlated electron systems exhibit various physical properties closely related to charge, spin, and orbital degrees of freedom; in f-electron systems, multipoles, which are combinations of spin and orbital degrees of freedom, play a major role. The centrosymmetric CeCoSi, which belongs to the non-symmorphic space group (P4/nmm), has attracted much attention from the viewpoint of the odd-parity multipoles below the phase transition temperature T0. Recently, a Ce 4f-driven antiferroquadrupolar order below T0 was proposed by a detailed study using single crystal samples, followed by a complete phase diagram and further clarification of the finite T0 ~12 K even at ambient pressure [1,2]. Subsequently, 59Co NMR revealed anomalies suggestive of quadrupolar order [3], and odd-parity multipole order was theoretically proposed [4]. However, a fundamental question has remained unsolved as to why the localized Ce 4f state is so sensitive to external pressure and why the T0 increases substantially. Here, we report the direct observation of the Fermi surfaces and electronic band dispersions of CeCoSi by angle-resolved photoelectron spectroscopy (ARPES) utilizing synchrotron radiation. The photon energy-dependent ARPES result shows that two- and three-dimensional Fermi surfaces coexist, being consistent with the result of the first-principles calculation. By the Ce 3d-4f resonant photoelectron spectroscopy and the high-resolution ARPES, Ce 4f level is found to be located quite close to the Fermi level (~10 meV), which explains why the pressure-sensitive feature of the phase transition. |
Wednesday, March 8, 2023 4:00PM - 4:12PM |
Q29.00006: Realizing lattice topological insulators and higher-order topological insulators on a quantum computer Ching Hua Lee The ascendency of quantum computing technologies, particularly cloud quantum computing, has made the physical realization of various elusive quantum Hamiltonians possible. In this talk, I shall discuss recent realizations of various topological states with the IBM quantum computer, including but not limited to the Kitaev chain, Chern states and higher-order topological states. To circumvent the limited qubit numbers of present-day NISQ devices, higher-dimensional noninteracting lattices are mapped onto a 1D interacting chain. This technique takes advantage of the quantum many-body nature of the quantum hardware in realizing higher-dimensional states of unprecedented complexity. |
Wednesday, March 8, 2023 4:12PM - 4:24PM |
Q29.00007: Thermal Conductivity of Single Crystal FeSi Eric J Lee-Wong Recent research on bulk high quality single crystal FeSi found a surface conducting state the develops below 19 K with no change to FeSi’s bulk properties [1] – this state resembles a surface metallic state and is reminiscent of topological insulator behavior. Studies on thin film FeSi samples have also observed surface ferromagnetic domains [2], bolstering the evidence for a surface state in FeSi. By measuring the thermal conductivity of single crystal FeSi at low temperature, we can probe the correlation to the Wiedemann-Franz law and potentially separate the surface conducting state behavior from any bulk behavior. We performed thermal conductivity measurements on high quality FeSi single crystals with typical sample cross sections of 1600 um2. Here we report experimental methods and results for thermal and electrical conductivity measured down to 1.8 K. |
Wednesday, March 8, 2023 4:24PM - 4:36PM |
Q29.00008: The Kane-Mele-Hubbard model in the Two-Particle Self-Consistent approach Dominik Lessnich, A.-M. S Tremblay, Roser Valenti The Kane-Mele model without interactions is well known to possess a quantized spin-Hall conductivity arising from topological effects of spin-orbit coupling (SOC). Adding a Hubbard interaction leads to a phase diagram that also features an anti-ferromagnetic phase. The interplay of anti-ferromagnetic spin fluctuations and topological properties can then be captured by our generalization of the Two-Particle Self-Consistent (TPSC) approach that includes the effect of spin-orbit coupling. TPSC is a many-body method, valid for weak to intermediate interaction strength that, with low computational effort, allows to investigate non-local correlation effects in interacting lattice models [1]. We present numerical results for the spin-Hall conductivity and discuss the role of anti-ferromagnetic spin fluctuations. |
Wednesday, March 8, 2023 4:36PM - 4:48PM |
Q29.00009: Towards Non-Invertible Anomalies from Generalized Ising Models Shang Liu, Wenjie Ji The 1d transverse-field Ising model, when projected to the Z2 symmetric sector, is known to have a noninvertible gravitational anomaly that can be compensated by the Z2 toric code model in 2d. In this work, we study the generalization of this type of bulk-boundary correspondence in a large class of qubit lattice models in arbitrary dimensions, called the generalized Ising (GI) models. We provide a systematic construction of exactly solvable bulk models, where the GI models can terminate on their boundaries. In each bulk model, any ground state is robust against local perturbations. If the model has degenerate ground states with periodic boundary condition, the phase is topological and/or fracton ordered. The construction generates abundant examples, including not only prototype ones such as Z2 toric code models in any dimensions no less than two, and the X-cube fracton model, but also more diverse ones. The boundary of the solvable model is potentially anomalous and corresponds to precisely only sectors of the GI model that host certain total symmetry charges and/or satisfy certain boundary conditions. We derive a concrete condition for such bulk-boundary correspondence. A generalized notion of Kramers-Wannier duality plays an important role in the construction. Also, utilizing the duality, we find an example where a single anomalous theory can be realized on the boundaries of two distinct bulk fracton models, a phenomenon not expected in the case of topological orders. |
Wednesday, March 8, 2023 4:48PM - 5:00PM |
Q29.00010: High Magnetic Field Behavior of Novel Phases in YbB12 Christopher A Mizzi, Mun K Chan, William A Phelan, Lucas A Pressley, Tyrel M McQueen, Priscila Rosa, Neil Harrison Large magnetic fields have dramatic effects on electron motion. In (semi)metallic systems, these effects are particularly pronounced because electron states are quantized into Landau levels causing oscillatory behavior in physical observables, known as quantum oscillations (QOs). QOs are important probes of electronic structure, but historically have been limited to (semi)metallic systems. As such, QOs in the magnetization and resistivity of YbB12 are surprising because YbB12 is nominally an insulator with small hybridization gaps at low temperatures. These observations in YbB12, and similar systems, are exciting owing to implications for topologically-protected surface states or a bulk neutral Fermi surface, but their origin is still not understood. In addition to these unconventional QOs, YbB12 hosts a strongly-correlated metallic state accessible by high fields. The possibility of a connection between the insulating ground state and field-induced metallic state remains unclear. |
Wednesday, March 8, 2023 5:00PM - 5:12PM Author not Attending |
Q29.00011: Phonon-induced breakdown of Thouless pumping in the Rice-Mele-Holstein model Suman Mondal, Eric Bertok, Fabian Heidrich-Meisner Adiabatic and periodic variations of the lattice parameters can make it possible to transport charge through a system even without net external electric or magnetic fields, known as Thouless charge pumping. The amount of charge pumped in a cycle is quantized and entirely determined by the system's topology, which is robust against perturbations such as disorder and interactions. However, coupling to the environment may play a vital role in topological transport in many-body systems. In this talk, we will discuss the topological Thouless pumping, where the charge carriers interact with local optical phonons. The semi-classical multi-trajectory Ehrenfest method is employed to treat the phonon trajectories classically and charge carriers quantum mechanically. We find a breakdown of the quantized charge transport in the presence of phonons. It happens for any finite electron-phonon coupling strength at the resonance condition when the pumping frequency matches the phonon frequency, and it takes finite phonon coupling strength away from the resonance. Moreover, there exist parameter regimes with non-quantized negative and positive charge transport. The modified effective pumping path due to electron-phonon coupling accurately explains the underlying physics. In the large coupling regime where the pumping disappears, the phonons are found to eliminate the staggering of the onsite potentials, which is necessary for the pumping protocol. |
Wednesday, March 8, 2023 5:12PM - 5:24PM |
Q29.00012: Miscibility relations in AV3Sb5 kagome superconductors; properties of single crystal (K,Rb,Cs)V3Sb5 alloys and dopants Brenden Ortiz, Andrea Capa-Salinas, Paul M Sarte, Ganesh Pokahrel, Yuzki Oey, Miles Knudtson, Stephen D Wilson, Ram Seshadri, Farnaz Kaboudvand Chemical tuning, either through alloying or doping, are fundamental ways to probe key structure-property relationships in complex materials. Here we investigate both alloying and doping in the AV3Sb5 kagome superconductors (A: K, Rb, Cs). We demonstrate full miscibility on the alkali site in powders, highlighting that the entire (K,Rb,Cs)V3Sb5 chemical space exists and further demonstrate our methods for growing (K,Rb,Cs)V3Sb5 single crystal alloys. Nonlinear changes in the charge density wave and superconducting temperature are tracked as a function of alkali composition. Analogous comparisons are made for our doped single crystals as a function of both n-type (Te, Cr) and p-type (Sn, Ti) dopants. |
Wednesday, March 8, 2023 5:24PM - 5:36PM |
Q29.00013: A combined THz and DC transport method to probe electronic phase-coexistence in complex material systems Gulloo L Prajapati, Sarmistha Das, Jan C Deinert, Dhanvir S Rana The coexistence of multiple phases in complex material systems is a common phenomenon. Consequently, unravelling the underlying mechanisms of phase-transitions in such systems becomes extremely difficult. One powerful approach to tackle this problem is real-time visualization of the growth and evolution of coexisting phases during the phase-transition. Here, we present a method to probe the evolution of electronic phase-coexistence by combining terahertz (THz) transport with DC transport. We demonstrate our novel methodology on rare-earth nickelate films, which exhibit a first-order metal-insulator transition (MIT). As we modulate the insulating/metallic domain sizes in the phase-coexistence region of the films by introducing a controlled amount of disorder, the DC transport measurement continues to detect the MIT. However, the signature of this transition in the THz transport measurement successively weakens and completely disappears above a critical limit of disorder. This disparity occurs due to the high sensitivity of THz radiation to those insulating/metallic domains whose sizes are comparable or greater than the THz probing wavelengths and its insensitivity to other smaller sized domains. Thus, exploiting this property of THz radiation in THz transport measurements, the evolution of electronic phase-coexistence can successfully be probed in a variety of material systems. |
Wednesday, March 8, 2023 5:36PM - 5:48PM |
Q29.00014: The Effects of High Magnetic Fields on the Magnetic Excitations of Kondo Insulators Peter Riseborough, Xiao Yuan Spin-Excitons are sharp branches of dispersive triplet excitations found at excitation energies within the gap of paramagnetic Kondo Insulators. The spin-excitons are precursor excitations to an antiferromagnetic instability. In the presence of a weak magnetic field, the excitations are expected to split into three branches. Here we examine excitation energies and intensity of the spin-exciton branches as a function of the applied magnetic field. We find that the energy splittings of the dispersion relation are proportional to the applied field, and that the intensity of the lower branch diminishes rapidly with increasing fields.. For strongly-bound spin excitons, the lower branch softens with increasing field becoming a Goldstone mode of a field induced antiferromagnet phase. Furthermore, we find that for weakly-bound spin-excitons, the application of a sufficiently large applied field causes the intensity of the lowest energy branch to drop to zero resulting in a doublet of excitations. |
Wednesday, March 8, 2023 5:48PM - 6:00PM |
Q29.00015: Classification of Fermionic Topological Orders from Congruence Representations Donghae Seo, Minyoung You, Gil Young Cho, Hee-Cheol Kim The fusion rules and braiding statistics of anyons in (2+1)D fermionic topological orders are characterized by the modular data of a super-modular category. On the other hand, the modular data of a super-modular category form a congruence representation of the Gamma_theta subgroup of the modular group SL_2(Z). We provide a method to classify the modular data of super-modular categories by first obtaining the congruence representations of Gamma_theta and then building candidate modular data out of those representations. We carry out this classification up to rank 10. We obtain both unitary and non-unitary modular data, including all previously known unitary modular data, and also discover new classes of modular data of rank 10. We also determine the central charges of all these modular data, without explicitly computing their modular extensions. |
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