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 N29: Strongly Correlated Systems, Including Quantum Fluids and Solids XI |
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Sponsoring Units: DCMP Chair: Omar Chmaissem, Northern Illinois University and Argonne National Laboratory Room: Room 221 |
Wednesday, March 8, 2023 11:30AM - 11:42AM |
N29.00001: Layered Metals as Polarized Transparent Conductors Carsten Putzke, Chunyu Guo, Vincent M Plisson, Martin Kroner, Thibault Chervy, Matteao Simoni, Pim Wevers, Maja D Bachmann, John R Cooper, Antony Carrington, Naoki Kikugawa, Jennifer Fowlie, Stefano Gariglio, Andrew Mackenzie, Kenneth S Burch, Atac Imamoglu, Philip J Moll The quest to improve transparent conductors balances two key goals: increasing electrical conductivity and increasing optical transparency. To improve both simultaneously is hindered by the physical limitation that good metals with high electrical conductivity have large carrier densities that push the plasma edge into the ultra-violet range. Transparent conductors are compromises between electrical conductivity, requiring mobile electrons, and optical transparency based on immobile charges to avoid screening of visible light. Technological solutions reflect this trade-off, achieving the desired transparencies by reducing the conductor thickness or carrier density at the expense of a lower conductance. Here we demonstrate that highly anisotropic crystalline conductors offer an alternative solution, avoiding this compromise by separating the directions of conduction and transmission. Materials with a quasi-two-dimensional electronic structure have a plasma edge well below the range of visible light while maintaining excellent in-plane conductivity. We demonstrate that slabs of the layered oxides Sr2RuO4 and Tl2Ba2CuO6+d are optically transparent even at macroscopic thicknesses >2mm for c-axis polarized light. Underlying this observation is the fabrication of out-of-plane slabs by focused ion beam milling. This work provides a glimpse into future technologies, such as highly polarized and addressable optical screens, that advancements in a-axis thin film growth will enable. |
Wednesday, March 8, 2023 11:42AM - 11:54AM |
N29.00002: Dielectric properties of plastically deformed strontium titanate Luka Rogic, Issam Khayr, Martin Greven, Damjan Pelc Recent studies demonstrate the promise of plastic deformation as a tool to manipulate the electronic properties of quantum materials [1]. Here we present the results of 4-terminal capacitance measurements of insulating, plastically deformed strontium titanate, SrTiO3. Significant differences compared to undeformed samples are clearly seen in the temperature dependence of the permittivity, where we observe evidence for a first-order phase transition close to ambient temperature. The transition is likely related to local ferroelectricity around dislocation structures, the existence of which was uncovered previously [1]. We also find a strong influence of an external magnetic fields on the transition, which points to a large magneto-electrical coupling that could be important for applications. |
Wednesday, March 8, 2023 11:54AM - 12:06PM |
N29.00003: Far-infrared study of electron-phonon coupling in metallic strontium titanate Noah Somun, Damjan Pelc, Luka Rogic, Sylvia L Griffitt, Ana Najev, Marin Spai?, Issam Khayr, Martin Greven Recently it was proposed that spin-orbit assisted electron-phonon coupling could be strong enough to explain superconducting pairing in metallic strontium titanate, SrTiO3 (STO). This coupling can be represented as a dynamic Rashba spin-orbit interaction and results in a complex hybridization between plasmon, phonon and electron spin-flip modes in an applied magnetic field. We studied samples of lightly doped STO using a quasi-optical far-infrared spectrometer, which allowed for continuous measurements of absorbed power in the sub-terahertz frequency range. Measurements were made with and without a magnetic field. Without magnetic field, we observed two soft infrared TO phonon modes, due to crystal-field splitting in the STO tetragonal phase, and detected changes in their frequencies and weights with increasing field. Moreover, we found that a phonon-like signal appears at frequencies consistent with the screened plasmon energy. These results qualitatively support the aforementioned hybridization and lay the foundation to determine the coupling strength and resolve the origin of superconductivity in STO. |
Wednesday, March 8, 2023 12:06PM - 12:18PM |
N29.00004: The electronic structure of HgBa2Can-1CunO2n+2+x cuprates: a first-principles study with the SCAN functional. Alpin N Tatan, Jun Haruyama, Osamu Sugino We study the electronic structure of HgBa2Can-1CunO2n+2+x cuprates by first-principles calculation with the strongly constrained and appropriately normed (SCAN) density functional [1]. We analyze the structural, electronic, and magnetic order evolution of these compounds upon variation of physical parameters such as number of copper-oxide layers or oxygen doping level, in comparison to past experiments/studies involving other theoretical methods. The enhanced density of states at Fermi level is demonstrated in our structures under suitable parameters that concur with the experimentally derived optimum conditions for superconductivity. We believe the improvements presented in this brief work [2] suggest a good prospect for furthering first-principles density-functional studies of cuprates in the future. |
Wednesday, March 8, 2023 12:18PM - 12:30PM |
N29.00005: Doping evolution of the pseudogap and charger order in Y1-xPrxBa2Cu3O7-δ John Y Wei, Chao C Zhang, Rainni K Chen, Min Gu Kang, Riccardo Comin Among the RBa2Cu3O7 (R = Y or rare earth) family of cuprates, Pr-doping is unique in that it systematically suppresses the superconductivity. Recently, resonant x-ray scattering studies of Y1-xPrxBa2Cu3O7-δ (YPrBCO) thin films observed an in-plane charge order whose onset temperature (TCO) increases monotonically with Pr-doping all the way to the Mott insulator limit (x = 1) [1], unlike other doped cuprates. The pseudogap is another type of electronic order commonly seen in the cuprates, but its evolution with Pr-doping in YPrBCO is not well understood. In this talk, we present new measurements of the pseudogap onset temperature (T*) made by electrical transport on YPrBCO thin films. We compare the evolution of T* and TCO versus Pr-doping, to elucidate the physical connection between these two types of order, and how they relate to the superconducting order over the entire phase diagram of YPrBCO. Finally, we examine spectral evidence for both the pseudogap and charge order, as manifested in such measurements as quasiparticle tunneling and angle-resolved photoemission spectroscopy. |
Wednesday, March 8, 2023 12:30PM - 12:42PM |
N29.00006: Many-Body Topological Quantum Chemistry Indices in 2D with Real Space Invariants Jonah Herzog-Arbeitman, Andrei B Bernevig, Zhida Song The topological phases of non-interacting fermions are understood from the perspective of topological quantum chemistry, and more recently from a spatially local formulation using Real Space Invariants (RSIs). This work generalizes the real space classification to interacting 2D states at integer fillings. We construct many-body local RSIs (the Noether charges of discrete symmetries) as the quantum numbers of a set of symmetry operators on open boundaries, but which are independent of the choice of boundary. Using the U(1) particle number, they yield many-body fragile topological indices, identifying which single-particle fragile states are many-body topological and which are trivial at weak coupling. To this end, we construct an exactly solvable Hamiltonian with single-particle fragile topology that is adiabatically connected to a trivial state through strong coupling. We then define global many-body RSIs on periodic boundary conditions. They reduce to Chern numbers in the band theory limit but also identify many strongly correlated stable topological phases with no single-particle counterpart. Finally, we show that the many-body RSIs appear as quantized coefficients of Wen-Zee terms in the topological response theory describing the phase. |
Wednesday, March 8, 2023 12:42PM - 12:54PM |
N29.00007: Fermions and Bosons as Emergent Particles in Fractional Quantum Hall Systems Bo Yang Strongly correlated topological systems in two-dimension serve as good platforms for realising quantum fluids of anyons, which are exotic particles with statistical behaviours different from either Fermions or Bosons. The fractional Quantum Hall (FQH) system is a good example, where anyons can be readily created and they are useful for the robust storing and manipulation of quantum information. The bulk edge correspondence and the conformal symmetry of the FQH systems, however, allow us to either fermionize or bosonize anyons in this two-dimensional manifold. We show explicit unitary transformations from the many-body electronic and anyonic wavefunctions to the emergent bosonic and fermionic product states. Using this approach we reveal interesting dynamical properties of anyons even in very simple FQH phases, and new families of bosonic QH phases as dual descriptions of their fermionic counterparts. By connecting to the well known composite fermion (CF) theory for the FQH systems, we show how exact model Hamiltonians can be constructed for the Jain series and interacting CF states, and how the CF states (including the composite fermi liquid) can be constructed without using the LLL projection. An interesting example is the construction of an Abelian, gapped model Hamiltonian where the Gaffnian model wavefunction is the \emph{exact} ground state, revealing the hidden connection between the CF theory and the pseudopotential/Jack polynomial formalism. We discuss the nature of particle statistics in 2D conformal Hilbert spaces in general, as well as their experimental implications. (References: arXiv:2207.12418, PRL 127, 126406, PRL 127, 046402). |
Wednesday, March 8, 2023 12:54PM - 1:06PM |
N29.00008: Elastoresistivity measurement of kagome metal CsV3Sb5 Zhaoyu Liu, Yue Shi, Qianni Jiang, Elliott W Rosenberg, Jonathan M DeStefano, Zhiwei Wang, Jiun-Haw Chu The Recently discovered kagome metal CsV3Sb5 has attracted enormous attention due to its nontrivial topological electronic structure and intertwined symmetry-broken states [1,2]. One central question is the nature of the broken symmetry associated with the charge density wave (CDW) onsets at T ~ 90K [3,4]. In this talk, I will present the measurement of elastoresistivity and elastocaloric effect of CsV3Sb5. Using three different techniques, the differential, the modified Montgomery and the transverse method, we precisely decomposed the elastoresistivity coefficient into different symmetry channels. We found that the isotropic elastoresistivity coefficient (i.e., m11+m12) increases substantially below the charge density wave transition temperature and becomes several times larger than the nearly temperature-independent anisotropic coefficient (i.e., m11-m12). Our results suggest that the charge density wave phase in CsV3Sb5 either does not break rotational symmetry or its broken rotational symmetry is decoupled from the anisotropic strain. |
Wednesday, March 8, 2023 1:06PM - 1:18PM |
N29.00009: Structure of domain walls in chiral spin liquids Yanqi Wang, Chunxiao Liu, Joel E Moore The chiral spin liquid is one of the canonical examples of a topological state of quantum spins coexisting with symmetry-breaking chiral order; its experimental realization has been actively discussed in the past few years. Here, motivated by the interplay between topology and symmetry breaking, we examine the physics of the interface between two chiral spin liquid domains with opposite chiralities. We show that a self-consistent mean-field description for the spinons exists that describes both the change of chirality at the domain wall and the gapless edge modes living on it. A Ginzburg-Landau theory for the domain wall is formulated based on the mean-field picture, from which we obtain the non-universal properties of the domain wall such as the wall width and tension. We show that the velocity of the topologically protected domain wall edge states can be accessed through the Jackiw-Rebbi mechanism. We further argue that the gapless modes at the edge contribute an extra, non-analytic |φ3| term to the domain wall theory, and find numerical evidence for this non-analyticity. |
Wednesday, March 8, 2023 1:18PM - 1:30PM |
N29.00010: Excitonic Chern insulator in a moiré lattice (Part1) Zhengchao Xia, Yihang Zeng, Bowen Shen, Roei Dery, Kenji Watanabe, Takashi Taniguchi, Jie Shan, Kin Fai Mak Characterization of thermodynamics properties is of great importance in the study of strongly correlated two-dimensional systems. While existing techniques rely on electrical measurement of thermodynamics, optical detection of thermodynamic quantities has not yet been reported. Compared to electrical measurement, optical measurement provides spatial resolution, time resolution and energy resolution. Here we report the first realization of optical characterization of thermodynamics properties by inserting an TMD exciton sensor close to the sample. The band edge of the exciton sensor is accurately determined by optical reflection spectroscopy on sensor 1s exciton resonance and actively adjusted through a feedback mechanism to the fermi level, providing a reference point for chemical potential readout in the sample. Furthermore, we extract other thermodynamics variables including charge compressibility, polarization, and magnetization from measured chemical potential of the sample through Maxwell’s relation. This technique provides a powerful platform for local thermodynamics measurement and has great potential in realizing spatially resolved transport measurement and time-resolved characterization of thermodynamics. |
Wednesday, March 8, 2023 1:30PM - 1:42PM |
N29.00011: Excitonic Chern insulator in a moiré lattice (part2) Yihang Zeng, Zhengchao Xia, Jie Shan, Kin Fai Mak Excitonic insulators form when the charge gap of insulators becomes smaller than the binding energy of an electron-hole pair (exciton); spontaneous emergence of an exciton fluid is expected. Near such band inversion point with small charge gap, topological bands with finite Chern numbers can also emerge. A natural question arises: is it possible to have a Chern insulator from an excitonic mechanism? The emergence of moiré materials with tunable band inversion and strong excitonic interactions provides a platform to address this question. Here, by combining local thermodynamic measurements and magneto-optical spectroscopy, we report experimental evidence of an excitonic Chern insulator in AB-stacked MoTe2/WSe2 moiré heterobilayers, which support electric-field-tuned band inversions. These combined measurements performed simultaneously on the same sample location are made possible by employing a new optical technique to readout the thermodynamic equations of states. At half-band-filling, spontaneous formation of interlayer excitons, accompanied by the emergence of a ferromagnetic Chern insulator, is observed before an electric-field-induced charge gap closure. The results provide direct evidence of an excitonic Chern insulator driven by Coulomb correlations, and open the door to realize topological exciton condensates. |
Wednesday, March 8, 2023 1:42PM - 1:54PM |
N29.00012: Superconductivity in the antiferromagnetic quantum critical metal in two dimensions Ashutosh K Singh, Francisco A Borges Zapata, Anton Borissov, Andres Felipe Schlief Raether, Sung-Sik Lee To understand the interplay between non-fermi liquid behaviours and the onset of superconductivity in quantum critical metals, one has to understand the dynamics of electrons that are subject to both singular interactions mediated by gapless collective modes and large-angle scatterings caused by superconducting fluctuations. For this purpose, the patch theory that includes only a small portion of Fermi surface is insufficient. We develop a field theoretic functional renormalization group formalism for full low-energy effective field theories of non-Fermi liquids that include all gapless modes around the Fermi surface. Applying this formalism to the non-fermi liquid that arises at the antiferromagnetic quantum critical metal in two dimensions, we explain how critical spin fluctuations cause electrons to lose coherence on the one hand and at the same time drive superconductivity by providing an attractive glue for pairing. |
Wednesday, March 8, 2023 1:54PM - 2:06PM Author not Attending |
N29.00013: Local order parameters and moire translation symmetry breaking of twisted bilayer graphene from local density of states Tomohiro Soejima, Kevin P Nuckolls, Jung Pyo Hong, Myungchul Oh, Michael P Zaletel, Ryan L Lee, Dillon Wong We develop a method to identify the nature of symmetry breaking in twisted bilayer graphene using atomically-resolved local density of states. We define a set of local order parameters that can be directly extracted from Fourier transform of the local density of states, and show that different theoretical candidate ground states of twisted bilayer graphene shows distinct symmetry breaking features. |
Wednesday, March 8, 2023 2:06PM - 2:18PM |
N29.00014: The role of electron correlations in the electronic structure of putative Chern magnet TbMn6Sn6 using correlated methods Abdulgani Annaberdiyev, Jaron T Krogel, Panchapakesan Ganesh A member of the RMn6Sn6 rare-earth family materials, TbMn6Sn6, recently showed experimental signatures of the realization of a quantum-limit Chern magnet. Despite the promising experimental results, theoretical studies with accurate electron correlations which probe these observations have been lacking. In this work, we use QMC and DFT+U calculations to examine the electronic structure of TbMn6Sn6. To do so, we optimize accurate, correlation-consistent pseudopotentials for Tb and Sn using CCSD(T) and CI methods. We find that DFT+U and single-reference QMC calculations suffer from the same overestimation of the magnetic moments as meta-GGA and hybrid density functional approximations. Our findings point to the need to either use improved orbitals, such as natural orbitals from CI, or to include multi-reference wave functions to capture the static correlations for an accurate prediction of magnetic properties. The necessity for multi-reference treatment is motivated by extrapolating the dynamic correlations to the exact limit. DFT+U with empirically adjusted Mn magnetic moments predict the Dirac crossing to be close to the Fermi level, within ~120 meV, in agreement with the experiments. |
Wednesday, March 8, 2023 2:18PM - 2:30PM |
N29.00015: Microwave reactance spectroscopy in two-dimensional materials Abhishek Banerjee, Zeyu Hao, Zhongying Yan, Mary Keenan, Thomas R Werkmeister, Andrew Zimmerman, Robert M Westervelt, Kin Chung Fong, Philip Kim The interplay of low-dimensionality and strong correlations can give rise to novel gapped ground states in graphene and transition metal dichalcogenide heterostructures. These states include symmetry-broken correlated insulators, topological insulators, and unconventional superconductors. While DC resistance measurements have been widely used to study these systems, reactance measurements in the microwave regime can shed new light on these phases and the phase-transitions between them. In this talk, I will discuss the design of a radio frequency (RF) reflectometry setup adapted for capacitance and inductance measurements in 2D materials. Challenges associated with microwave measurements in 2D devices such as large contact resistances, RF leakage, impedance matching, and device design are addressed. Preliminary measurement results are discussed. |
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