Bulletin of the American Physical Society
APS March Meeting 2023
Las Vegas, Nevada (March 510)
Virtual (March 2022); Time Zone: Pacific Time
Session S22: Strong Electronic Correlations in Topological Materials: Theory and Experiment 
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Sponsoring Units: DCMP Chair: Brian Moritz, SLAC National Accelerator Laboratory Room: Room 214 
Thursday, March 9, 2023 8:00AM  8:12AM 
S22.00001: Resolving the electronic structure of Kagome metal ScV_{6}Sn_{6} Yuan Zhu, Guoxin Zheng, Kaila G Jenkins, Dechen Zhang, KuanWen Chen, Matthew A Cothrine, Richa Pokharel Madhogaria, Shirin Mozaffari, William R Meier, David G Mandrus, Lu Li

Thursday, March 9, 2023 8:12AM  8:24AM 
S22.00002: Quantum oscillations of Kagome Metal ScV_{6}Sn_{6} in intense magnetic field Kaila G Jenkins, Yuan Zhu, Guoxin Zheng, Dechen Zhang, Richa Pokharel Madhogaria, Matthew A Cothrine, Shirin Mozaffari, William R Meier, David G Mandrus, Lu Li Quantum oscillations in strong magnetic fields give us direct insight into the bandstructure of solids via the quantization of electron motion. The Kagome lattice structure allows for topologically protected surface states that can be realized via the frequency of observed quantum oscillations. A crucial question remains about the fate of the small orbits when the magnetic field is strong enough to push the electronic state to the quantum limit. By utilizing proximity detector oscillators (PDOs) in a 65 T pulsed field, we resolved strong quantum oscillations corresponding to Fermi surface orbits in ScV_{6}Sn_{6}. The study will be compared with the Landau level indexing mapping with the quantum oscillation results in the DC fields. 
Thursday, March 9, 2023 8:24AM  8:36AM 
S22.00003: Differentiating Dirac from nonDirac bands in Kagome metal ScV_{6}Sn_{6} Guoxin Zheng, Yuan Zhu, Kaila G Jenkins, Dechen Zhang, KuanWen Chen, Matthew A Cothrine, Richa Pokharel Madhogaria, Shirin Mozaffari, William R Meier, David G Mandrus, Lu Li The Kagome lattice is an ideal platform to present topological properties within the strong electron correlation regime due to its special geometric structure. The Kagome metal family AV_{3}Sb_{5} (A=K, Cs, Rb) has been discovered recently to host the entanglement of charge density wave (CDW), superconductivity, and topological electronic structure. Here, we measured another Kagome metal ScV_{6}Sn_{6}, which also exhibits CDW ordering without superconductivity in the ground state. We conducted the resistance and magnetic torque measurements at base temperature to search the quantum oscillations in order to map the Fermi surface. The Landau Level indexing resolved the trivial and nontrivial Berry phases from different bands. We will compare the observations with the electronic structure modeling to shed light on the “Diracness” of the related bands. 
Thursday, March 9, 2023 8:36AM  8:48AM 
S22.00004: Topological flat bands in a kagome lattice multiorbital system Satoshi Okamoto, Narayan Mohanta, Elbio R Dagotto, Donna Sheng Flat bands and dispersive Dirac bands are known to coexist in the electronic bands in a twodimensional kagome lattice. Including the relativistic spinorbit coupling, such systems often exhibit nontrivial band topology, allowing for gapless edge modes between flat bands at several locations in the band structure, and dispersive bands or at the Dirac band crossing. Here, we theoretically investigate the electronic property of a multiorbital system on a kagome lattice. We found that the multiorbital kagome model with the atomic spinorbit coupling naturally supports topological bands characterized by nonzero Chern numbers C, including a flat band with C =1. We further investigate the effect of Coulomb repulsive interactions. When such a flat band is 1/3 filled, the nonlocal repulsive interactions induce a fractional Chern insulating state. Thus, the multiorbital system on a kagome lattice is a versatile platform to explore the interplay between nontrivial band topology and electronic interaction. We also discuss the possible realization of our findings in real kagome materials. 
Thursday, March 9, 2023 8:48AM  9:00AM 
S22.00005: Tunable Mott Dirac and kagome bands engineered on 1TTaS_{2} KyungHwan Jin Strongly interacting electrons in hexagonal and kagome lattices exhibit rich phase diagrams of exotic quantum states, including superconductivity and correlated topological orders intermixed with magnetic orders. However, material realizations of these electronic states have been scarce in nature or by design. Here, we theoretically propose an approach to realize artificial hexagonal and kagome lattices by metal adsorption on a 2D Mott insulator 1TTaS_{2}. Alkali, alkalineearth, and group13 metal atoms are deposited stably in (√3×√3)R30° and 2×2 TaS_{2} superstructures of honeycomb and kagomelattice symmetries exhibiting Dirac and kagome bands, respectively. The strong electron correlation of 1TTaS_{2} drives the honeycomb and kagome systems into correlated topological phases described by KaneMeleHubbard and kagomeHubbard models with nontrivial Z_{2} invariant and helical edge modes, respectively. We further show that the 2/3 or 3/4band filling of these Mott Dirac and flat bands can be achieved with a proper concentration of Mg adsorbates. Our proposal may be readily implemented in experiments, offering an attractive condensedmatter platform to exploit the interplay of topological order and superconductivity under the strong electron correlation. 
Thursday, March 9, 2023 9:00AM  9:12AM 
S22.00006: Nematic susceptibility in the kagome superconductor CsV_{3}Sb_{5} Kenichiro Hashimoto, Asato Onishi, Yoichi Kageyama, Masaki Roppongi, Kota Ishihara, Brenden Ortiz, Stephen D Wilson, Takasada Shibauchi The recently discovered kagome superconductors AV_{3}Sb_{5} (A = K, Rb, Cs) exhibit unusual chargedensitywave (CDW) order with time reversal and rotational symmetry breaking, which may be related to chiral loop current order. In order to clarify the origin of the nontrivial CDW order, it is essential to clarify the relationship between timereversal symmetry breaking and nematicity. Here, we report on the nematic susceptibility of CsV_{3}Sb_{5}. We performed elastoresistance measurements in two different configurations (fourprobe and Montgomery methods), from which we obtained the same results for elastoresistance coefficients with A_{1g} (symmetric) and E_{2g} (nematic) symmetries. Both elastoresistance coefficients exhibit a steep jump at T_{CDW}, reflecting the occurrence of a firstorder phase transition at T_{CDW}. The E_{2g} elastoresistance coefficient corresponding to the nematic susceptibility is temperatureindependent below T_{CDW}, indicating that the nematic state in CsV_{3}Sb_{5} is not evenparity ferroic order (q ≠ 0). In contrast, the elastoresistance coefficient with symmetric A_{1g} symmetry shows a broad peak structure around 30 K, which may be related to an anomaly reported in other experiments such as nonreciprocal transport measurements. 
Thursday, March 9, 2023 9:12AM  9:24AM 
S22.00007: Charge density wave interaction in a Kagomehoneycomb antiferromagnet Sen Shao, JiaXin Yin, Ilya Belopolski, Jingyang You Recent experiments report a charge density wave (CDW) in the antiferromagnet FeGe, but the nature of charge ordering, and the associated structural distortion remains elusive. Here, we unravel the structural and electronic properties of FeGe through indepth firstprinciples calculations. Our proposed 2×2×1 CDW, which is driven by the nesting of the hexagonal features of the Fermi surface, accurately captures atomic topographies observed via scanning tunneling microscopy as well as the enhancement of the kagomeFe magnetic moment upon transition into the CDW phase. In contrast to earlier studies, we show that the coupling of CDW and magnetism results in the motions of Ge atoms and FeGe exhibits a generalized Kekul'e distortion in the Ge honeycomb atomic layers. Our results set the stage for further exploration of the topological nature of the ground state of magnetic kagomehoneycomb lattices and their implications for novel transport, magnetic, and optical responses. 
Thursday, March 9, 2023 9:24AM  9:36AM 
S22.00008: Electron correlations and charge density wave in the topological kagome metal FeGe Chandan Setty, Christopher A Lane, Lei Chen, Haoyu Hu, Jianxin Zhu, Qimiao Si Recently, a charge density wave was discovered in the magnetic binary kagome metal FeGe [1]. 
Thursday, March 9, 2023 9:36AM  9:48AM 
S22.00009: Topological charge density waves in MoTe2/WSe2 moiré superlattices Bowen Shen, Tingxin Li, Wenjin Zhao, Lizhong Li, Shengwei Jiang, Jie Shan, Kin Fai Mak Transition metal dichalcogenide (TMD) semiconductor moiré system has been demonstrated as a versatile platform for studying exotic physics such as Hubbard physics and KaneMele physics. ABstacked MoTe2/WSe2 moiré system has enabled both optical and transport studies and shown vivid phase diagram such as topological phase transition at filling 1. Here we report a new Chern state at fractional filling with well quantized Hall resistance and vanishing longitudinal resistance in ABstacked MoTe2/WSe2. It is consistent with a topological charge density wave (CDW) state with spontaneously broken translational symmetry and a nonzero Chern number. Transport measurements further show that this topological CDW state is closely related to Kondo breakdown. More theoretical studies of the origin of this topological CDW state and the interplay between it and Kondo physics are needed. 
Thursday, March 9, 2023 9:48AM  10:00AM 
S22.00010: Topological moiré minibands and correlated Chern insulator from periodically confined massive Dirac fermions Ying Su, Heqiu Li, Chuanwei Zhang, Kai Sun, Shizeng Lin Strong electronic correlation in topological flat minibands renders moiré superlattices fascinating for accessing novel quantum states. Here we demonstrate a generic mechanism to realize topological flat minibands by confining massive Dirac fermions in a periodic moiré potential, which can be potentially realized in a heterobilayer of transition metal dichalcogenides. We show that the topological phase can be protected by the symmetry of moiré potential and survive to arbitrarily large Dirac band gap. We take the MoTe_{2}/WSe_{2} heterobilayer as an example and find that the topological phase can be driven by a vertical electric field. By projecting the Coulomb interaction onto the topological fat minibands, we identify a correlated Chern insulator at half filling and a quantum valleyspin Hall insulator at full filling. Our work clarifies the importance of Dirac structure for the topological minibands and unveils a general strategy to design topological moiré materials. 
Thursday, March 9, 2023 10:00AM  10:12AM 
S22.00011: Interactioninduced Quantum Anomalous and Spin Hall Mott Insulators: beyond Z_2 topology Peizhi Mai, Jinchao Zhao, Ben Feldman, Philip W Phillips We introduce interactions into two general models for quantum spin Hall physics. Although the traditional picture is that such physics appears at halffilling, we show that in the presence of strong interactions, the quarterfilled state instead exhibits the quantum spin Hall effect with spin Chern number $C_s=1$. A topological Mott insulator is the underlying cause that lies outside the standard $mathbb Z_2$ topological classification. An intermediate interacting regime emerges that exhibits a quantum anomalous Hall effect when the lower band is `flat'. This state transitions to the quantum spin Hall effect once the interactions are sufficiently large. We show that this intermediate regime is consistent with the simultaneous observation in transition metal dichalcogenide moir{'e} materials of a quantum anomalous Hall phase at quarter filling and a quantum spin Hall effect at halffilling. The valley coherence seen in such moir{'e} systems also matches expectations from a simple bilayer extension of our results. 
Thursday, March 9, 2023 10:12AM  10:24AM 
S22.00012: Probing interaction effects at a topological crystalline step edge by Scanning tunneling Microscopy and Scanning tunneling Spectroscopy Souvik Das, Glenn Wagner, Johannes Jung, Artem Odobesko, Felix Küster, Florian Keller, Jedrzej Korczak, Andrzej Szczerbakow, Tomasz Story, Stuart Parkin, Ronny Thomale, Titus Neupert, Matthias Bode, Paolo Sessi Topological Crystalline Insulators (TCIs) are the class of materials in which the topological nature of electronic structure arises from crystal symmetries. With the realization of a TCI phase in Pb_{1x}Sn_{x}Se it was perceived that the step edges in TCIs can be viewed as predecessors of higherorder topology, as they embody onedimensional (1D) edge channels embedded in an effective threedimensional electronic vacuum emanating from the TCI. Here we use scanning tunneling microscopy and spectroscopy to investigate the behavior of these 1D stepedge channels under the influence of doping. By doping distinct 3d adatoms in Pb_{1x}Sn_{x}Se we observed that once the energy position of the 1D stepedge mode is brought close to the fermi level, a new correlation gap starts to open. Our experimental findings are rationalized in terms of enhanced interaction effects since the electron density of states is collapsed to a 1D channel. This enables us to realize a unique system to study how topology and manybody electronic effects intertwine. 
Thursday, March 9, 2023 10:24AM  10:36AM 
S22.00013: Phase interference for probing topological fractional charge in a TIbased Josephson junction array Daan Wielens, Martijn Lankhorst, Tjerk Reintsema, Sietse Reintsema, Carlos Marques do Rosário, Chuan Li, Alexander Brinkman Fractional charges can be induced by magnetic fluxes at the interface between a topological insulator (TI) and a typeII superconductor due to axion electrodynamics [1]. In a Josephson junction array with a hole in the middle, these electronic states can have phase interference in an applied magnetic field with 4×2π period, in addition to the 2π interference of the Cooper pairs. 
Thursday, March 9, 2023 10:36AM  10:48AM 
S22.00014: Fieldanisotropic geometrical Hall effect via fd exchange fields in doped pyrochlore molybdates Hikaru Fukuda, Kentaro Ueda, Yoshio Kaneko, Ryosuke Kurihara, Atsushi Miyake, Kosuke Karube, Masashi Tokunaga, Yasujiro Taguchi, Yoshinori Tokura Topological spin textures have been proven to play an important role in the quantum electromagnetic properties. For instance, as a conduction electron is coupled with noncoplanar localized spins, its wave function is endowed with the Berry phase proportional to the solid angles subtended by the neighboring spins, i.e., the scalar spin chirality. The emergent magnetic field (Berry curvature) acts on the conduction electrons, giving rise to unconventional geometrical Hall effect [1]. However, few studies have been done on the geometrical Hall effect in the weak coupling case where no longrange magnetic order exist at zero field. 
Thursday, March 9, 2023 10:48AM  11:00AM 
S22.00015: Strong interactions in twisted bilayer graphene at the magic angle Khagendra Adhikari, Kangjun Seo, Kevin S Beach, Bruno Uchoa Twisted bilayer graphene (TBG) has been an active area of research due to its promise as a novel material with remarkable tunable properties. We perform a fully selfconsistent HartreeFock calculation on the lattice accounting for the Coulomb interaction among all the sites(more than 10,000) of the moiré unit cell at the magic angle. We derive the fully selfconsistently reconstructed bands at the HartreeFock level as a function of the filling factor. Considering rotations around AA sites, which permit constructing exponentially localized Wannier orbitals without topological obstructions, we derive an effective lattice model for the minibands of TBG accounting for spin and valley quantum numbers. We numerically address their possible manybody insulating phases at various filling factors. 
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