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 D29: Strongly Correlated Systems, Including Quantum Fluids and Solids I |
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Sponsoring Units: DCMP Chair: Jianhao Zhang, The Pennsylvania State University Room: Room 221 |
Monday, March 6, 2023 3:00PM - 3:12PM |
D29.00001: Diagnostics for plasmon satellites and Hubbard bands in transition metal oxides Steffen Backes, Hong Jiang, Silke Biermann The high energy spectral features of strongly correlated materials so far have not received as much as attention as the low energy features. Well established is the picture of a correlated metal, which exhibits a renormalized quasi-particle peak at the Fermi level, with a transfer of spectral weight into upper and lower Hubbard bands that are separated by the low energy static value of the Coulomb interaction U. Recently, this picture has become blurred with the rise in interest in systems which show additional plasmonic satellites at higher energies as well as close to the Fermi level. This renders the identification of spectral features of correlated electron materials non-trivial, since plasmonic satellites are not captured by static mean-field or static Hubbard-type interaction pictures. We will show how to distinguish these two types of satellites in the spectral function within modern ab-initio calculations based on the GW approximation combined with dynamica mean-field theory (GW+DMFT). Using this scheme we analyze the transition metal oxides SrVO3 and SrMoO3 which we find to exhibit both Hubbard and plasmonic satellites at very similar energetic positions. |
Monday, March 6, 2023 3:12PM - 3:24PM |
D29.00002: Subsystem symmetry defects Danny S Bulmash, Leo Radzihovsky Subsystem symmetries, whose generators only act on rigid lower-dimensional subregions of space, impose highly nontrivial constraints on physical systems like restricted mobility of their symmetry charges. We investigate the properties of defects of subsystem symmetries, focusing particularly on the interplay of translation symmetry and subsystem symmetry. We also discuss connections between subsystem symmetries and higher-form global symmetries. |
Monday, March 6, 2023 3:24PM - 3:36PM |
D29.00003: Exploring many-body spectral properties of strongly correlated electron-phonon systems via tensor network methods Martin Grundner Recent progress by some of us allowed to push the frontier of the description of bosonic degrees of freedom with tensor network methods. In this work we present an improvement to existing time evolution methods especially aimed for large local Hilbert spaces O(100). With this method we are able to efficiently describe both the local and global dynamic of excitations/quenches allowing us to explore yet uncharted territory of electron phonon coupling. In particular we investigate dynamic properties of the Hubbard-Holstein model. We shed light to the importance of the many-body character of spectral quantities, such as the optical conductivity and discuss the impact of optical pulses acting upon the ground state. |
Monday, March 6, 2023 3:36PM - 3:48PM Author not Attending |
D29.00004: Realizing quantum anomalous Hall insulator of composite fermions in twisted bilayer graphene Guangyue Ji, Junren Shi We theoretically study the realization of quantum anomalous Hall insulator (QAHI) of composite fermions (CFs) in the twisted bilayer graphene (TBG) system. We show that the moiré pattern in TBG could provide a tunable effective periodic potential necessary for the realization, without the need of imposing an additional superstructure as in the conventional GaAs system. It makes the TBG an ideal platform for realizing the QAHI of CFs. Based on the Dirac CF theory, we establish the phase diagram with respect to tunable experimental parameters.We find that the topological property of the system depends critically on the orbital magnetic susceptibility of CFs, which is not specified in the pristine Dirac CF theory and has to be introduced as an extra parameter. Thus, the experimental realization of QAHI of CFs would be helpful for clarifying the issue, i.e., the magnetic property of CFs. |
Monday, March 6, 2023 3:48PM - 4:00PM |
D29.00005: Coherent Transport vs. Realistic Phonons: Dissipation-Induced Bipolaron Localization Mattia Moroder, Martin Grundner, Sam Mardazad, François Damanet, Ulrich Schollwöck, Thomas Köhler, Sebastian Paeckel, Stuart Flannigan Recent advances in numerical methods significantly pushed forward the understanding of electrons coupled to quantized lattice vibrations. At this stage, it becomes increasingly important to also account for effects of physically inevitable environments. In this talk, I will present a study of the Hubbard-Holstein Hamiltonian that describes a prototypical model to study the transport properties of a large class of materials characterized by strong electron-phonon coupling, in contact to a dissipative environment. Even in the one-dimensional and isolated case, simulating the quantum dynamics of such a system with high accuracy is very challenging due to the infinite-dimensionality of the phononic Hilbert spaces. The difficulties tend to become even more severe when considering an incoherent coupling of the phonon-system to an environment. For this reason, the effects of dissipation on the conductance properties of such systems have not been investigated systematically so far. In this article, we close this gap by combining the non-Markovian hierarchy of pure states method and the Markovian quantum jumps method with the newly introduced projected purified density- matrix renormalization group, creating powerful tensor network methods for dissipative quantum many-body systems. Investigating their numerical properties, we find a significant speedup up to a factor ∼ 30 compared to conventional tensor-network techniques. We apply these methods to study quenches of the Hubbard-Holstein model, aiming for an in-depth understanding of the formation, stability, and quasi-particle properties of bipolarons. Our results show that in the metallic phase, dissipation localizes the bipolarons. However, the bipolaronic binding energy remains mainly unaf- fected, even in the presence of strong dissipation, exhibiting remarkable bipolaron stability. These findings shed new light on the problem of designing real materials exhibiting phonon-mediated high-TC superconductivity. |
Monday, March 6, 2023 4:00PM - 4:12PM |
D29.00006: Structural transition and possible orbital order in a trirutile compound Narendirakumar Narayanan, Duminda Sanjeewa, Thomas W Heitmann, Dehong Yu, Yun Liu, Garry McIntyre The interplay between orbital, lattice and spin degrees of freedom is a fundamental ingredient for exotic phenomena such as colossal magnetoresistance (CMR), metal-insulator transitions (MIT), multiferroicity or superconductivity, which can be tuned by external parameters. Prominent examples are the manganates R1-xAxMnO3, which exhibit CMR for R=La accompanied by MIT transition upon heating above ferromagnetic ordering at an optimal doping level (A) and multiferroicity for smaller R, or lower dimensional cuprates, which exhibit superconductivity upon doping the antiferromagnetic parent compounds. In both cases the ions Mn3+ and Cu2+ are Jahn-Teller active and emphasize the importance of orbital degrees of freedom. The related phenomena accompanying Jahn-Teller distortion is the orbital ordering (OO), which in analogous to spin ordering, is a symmetry breaking due to the localized orbital occupation. Whereas LaMnO3 and La2CuO4 are compounds exhibiting OO in partially filled eg levels, LaTiO3 is an example for partially filled t2g levels. In this work the lower temperature structural transition in the trirutile CrTa2O6 with a rare Jahn-Teller active ion Cr2+ is investigated in terms of the OO by neutron diffraction and theoretical modeling. |
Monday, March 6, 2023 4:12PM - 4:24PM |
D29.00007: Nanodiffraction imaging of ionically controlled phase separation in cobaltite heterostructures Scott Smith, Roopali Kukreja, Yayoi Takamura, Martin Holt, Tao Zhou Controlling ionic distribution and stoichiometry in complex oxide heterostructures has been utilized to significantly alter and tune functional properties of complex oxide thin films. Recently, deposition of a strong oxygen getter on top of an oxide thin film has emerged as a novel way to tailor oxygen stoichiometry and nanoscale functional properties. In this talk I will focus on Al/La0.67Sr0.33CoO3 (LSCO) heterostructures, due to their high oxygen ion conductivity and coupled magnetic and electronic properties, which are strongly dependent on oxygen stoichiometry. This combination of properties enables ionic control over functional properties in LSCO thin films through the influence of oxygen extracting layers such as Al. We utilize x-ray nanodiffraction to directly image the nanoscale morphology and local strain states of LSCO thin films as they are transformed from the equilibrium perovskite phase to the metastable brownmillerite (BM). Our studies show the coexistence of perovskite and BM phases, with formation of narrow and extended BM filaments as a function of getter layer thickness. These studies provide a nanoscale survey of both the morphology of the phase separation and the accompanying local strain states of these features, and compares the effects of different getter layers such as Gd and Al. |
Monday, March 6, 2023 4:24PM - 4:36PM |
D29.00008: Effect of zinc impurities on the thermal Hall conductivity of Cu3TeO6 Ashvini Vallipuram, Lu Chen, Emilie Dufault, Fazel Tafti, Louis Taillefer Cu3TeO6 (CTO) is a cubic antiferromagnetic insulator whose large negative thermal Hall conductivity (κxy) has been attributed to phonons [1], on the basis, for example, that κxy(T) mirrors the phonon dominated thermal conductivity κxx(T), with both peaking at the same temperature. |
Monday, March 6, 2023 4:36PM - 4:48PM |
D29.00009: Spatially Distributed Ramp Reversal Memory in VO2 Alexandre Zimmers, Sayan Basak, Yuxin Sun, Melissa Alzate Banguero, Pavel Salev, IVAN K SCHULLER, Lionel Aigouy, Erica W Carlson We use optical microscopy to image spatial maps of accumulated memory as a thin film of VO2 is repeatedly driven partway through its temperature-driven insulator-to-metal transition. By mapping for the first time the spatial structure of metal and insulator patches during a temperature ramp reversal sequence, the location and shape of accumulated memory was tracked after each hysteresis subloop, revealing the internal structure of the ramp reversal memory effect in this material. Our measurements demonstrate that new insulating regions appear through front propagation starting at insulator-metal boundaries. Surprisingly, our transition temperature maps reveal that memory is also stored deep inside the insulating and metallic clusters throughout the entire sample surface. We show that the non-volatile memory is globally reset by large temperature sweeps completed afterwards. We have developed a new model based on defect motion that accounts for the observed memory writing and subsequent erasing over the entire sample surface. By spatially mapping the location and character of non-volatile memory encoding in VO2, our results pave the way toward directly addressing local regions of VO2 in order to optimize neuromorphic memory elements. |
Monday, March 6, 2023 4:48PM - 5:00PM |
D29.00010: Defect Motion as a Driver of Ramp Reversal Memory in VO2 Yuxin Sun, Sayan Basak, Erica W Carlson, Pavel Salev, IVAN K SCHULLER, Melissa Alzate Banguero, Lionel Aigouy, Alexandre Zimmers Recently a new ramp reversal memory effect was observed in VO2, in which the resistivity was observed to increase by 20% upon applying a particular temperature sequence. One possible microscopic mechanism for the phenomenon is that "scars" accumulate wherever the metal-insulator domain walls reverse direction. [Vardi et al., Adv. Mater., 2017] By using optical microscopy to track the evolution of metal and insulator domains in VO2 during the ramp reversal temperature protocol, we find that memory also accumulates deep inside the metal/insulator patches rather than only at phase boundaries, which was not foreseen by the "scar" model. We develop a new model based on defect motion during the ramp reversal protocol, using the diffusion-segregation equation. Our calculations show that memory can happen deep inside the metallic and insulating regions and that certain regions in the sample can have a lowered transition temperature rather than a raised one, in agreement with our optical microscopy data. Our results pave the way toward using this "non-volatile" memory effect to mimic synaptic behavior for neuromorphic computing. |
Monday, March 6, 2023 5:00PM - 5:12PM |
D29.00011: Stochasticity in coupled spiking nano-oscillators Erbin Qiu Spiking oscillations can be generated by volatile resistive switching of VO2 devices which undergo an insulator-to-metal transition in response to a DC electrical voltage. We observe that increasing the coupling strength between VO2 based spiking oscillators produces stochastic disruptions in the synchronized spiking sequence. The stochastic behavior occurs for electrical as well as thermally coupled oscillators. This behavior is in a stark contrast with conventional harmonic oscillators, in which a stronger coupling leads to a more robust synchronization. The demonstration is simple, clear, straightforward, and unexpected. These results could greatly benefit researcher who work on understanding the basic science of coupled systems, develop practical implementation of nontraditional computational algorithms and study collective behavior of complex neuronal systems. This stochastic synchronization strongly resembles coupling of biological neurons and has broad relevance in many fields. |
Monday, March 6, 2023 5:12PM - 5:24PM |
D29.00012: Electronic and optical properties of Ti2O3 films Haoyue Jiang, David J Lahneman, Heungsoo Kim, Scott A Mathews, Alberto Pique, M.Mumtaz Qazilbash Bulk single crystals of titanium sesquioxide (Ti2O3) exhibit a thermally-driven metal-to-insulator transition (MIT) between 400-500 Kelvin without a structural phase transition. It is thought that strong electron-electron correlations and charge density wave order contribute to the MIT. Corundum structured Ti2O3 films were successfully grown on sapphire substrates by using pulsed laser deposition. X-ray diffraction, Raman spectroscopy, and atomic force microscopy were employed for the structural characterization of the films. Infrared and optical spectroscopy combined with temperature dependent resistivity measurements provided insight into the optical and electronic properties of the films. We shall present data on the structural, electronic, and optical properties of the Ti2O3 films and discuss how substrate-induced strain and the morphology of the films affect these properties when compared to bulk single crystals of Ti2O3. |
Monday, March 6, 2023 5:24PM - 5:36PM |
D29.00013: Deep Learning Hamiltonians from Disordered Image Data in Quantum Materials Melissa Alzate Banguero, Sayan Basak, Lukasz Burzawa, Forrest Simmons, Pavel Salev, Lionel Aigouy, Muhammad M Qazilbash, IVAN K SCHULLER, Dmitri N Basov, Alexandre Zimmers, Erica W Carlson Current advancements in surface probes have allowed researchers to have a large availability of images of quantum materials over different lengths and time scales. Those images have revealed the formation of intricate patterns as some materials approach criticality. In such cases, the spatial structure should encode information about interactions, dimensionality, and disorder – a spatial encoding of the Hamiltonian driving the pattern formation. With the well-known capabilities of deep learning techniques for image recognition, we have developed a framework to recognize the underlying physics that best describes the complex pattern formation in a film of VO2 during the metal-to-insulator transition. In this talk, we will go through the steps in developing the deep learning model: the selection of the Hamiltonians and the patterns they form, the data preparation, and the multi-label classification of images using a Convolutional Neural Network. We then vet this procedure using SNIM maps. Finally, we apply this method to new optical microscopy maps. Using our results, we propose a new machine learning based criterion for diagnosing a physical system’s proximity to criticality. |
Monday, March 6, 2023 5:36PM - 5:48PM |
D29.00014: Free Fermion Symmetry Breaking and a Long Exact Sequence in K-Theory Cameron Krulewski, Leon Liu, Ryan Thorngren We study symmetry breaking for free fermions. Specifically, we show how three processes |
Monday, March 6, 2023 5:48PM - 6:00PM |
D29.00015: Title:- Emergent symmetry in the renormalization group flow trajectories of extended Hubbard model in Bernal bilayer graphene Sk Asrap Murshed, Bitan Roy Abstract:- Due to quadratic touching of filled valence and empty conduction bands, yielding a finite density of states at low energies, Bernal stacked bilayer graphene constitutes an ideal platform to capture asymptotic freedom and BCS instabilities in the global phase diagram of extended Hubbard model for an interacting electronic fluid therein. Performing a leading order renormalization group (RG) analysis, we show that when an extended honeycomb-Hubbard model causes BCS instabilities of the disordered electronic ground state toward the nucleation of various competing ordered states, internal symmetry among distinct microscopic phases emerges along the RG flow trajectories. Paradigmatic cases include, for example, symmetry restoration between the layer antiferromagnet and Kekule (a) current as well as (b) pair-density-wave orders, enriching the emergent SO(5) among them with the `color degeneracy'. We map out all such RG flow trajectories through which the system can develop ordered states and the restoration of emergent enlarged symmetries along such RG paths. We also identify the footprint of such high-symmetry RG flow trajectories on various instructive cuts of the microscopic extended Honeycomb-Hubbard model on Bernal bilayer graphene. |
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