Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session D63: Charge Order and Charge Density WavesRecordings Available
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Sponsoring Units: DCMP Chair: Natalia Drichko, Johns Hopkins University Room: Hyatt Regency Hotel -Grant Park A |
Monday, March 14, 2022 3:00PM - 3:12PM |
D63.00001: Cryogenic electron microscopy of intra-unit-cell charge order textures in a manganite Ismail El Baggari, David J Baek, Michael J Zachman, Di Lu, Yasuyuki Hikita, Harold Y Hwang, Elizabeth A Nowadnick, Lena F Kourkoutis Charge-ordered states involve a complex interplay between charge, spin, orbital and lattice degrees of freedom. The intra-unit-cell arrangement within charge order superlattices (site vs bond order) can lead to even richer physics by breaking additional symmetries and allowing novel couplings. Here we use atomic-resolution cryogenic scanning transmission electron microscopy (cryo-STEM) to visualize charge-ordered states in a half-doped manganite (Nd1/2Sr1/2MnO3). In addition to observing that the system hosts site-centered charge ordering, we discover the nanoscale coexistence of an intermediate state which mixes site and bond orders. In agreement with theoretical proposals, we confirm that this intermediate state breaks inversion symmetry. Finally we show that nonlinear couplings of distinct lattice modes locally control the selection between these competing charge order states. |
Monday, March 14, 2022 3:12PM - 3:24PM |
D63.00002: First-principles study of metastable charge ordering states in La1/3Sr2/3FeO3 Nam H Nguyen, Hyowon Park, Vijay R Singh L1/3Sr2/3FeO3 exhibits the metal-to-insulator transition accompanying both antiferromagnetic and charge ordering states with the Fe-O bond disproportionation below T=200K. |
Monday, March 14, 2022 3:24PM - 3:36PM |
D63.00003: Charge-order dynamics in underdoped La1.6-xNd0.4SrxCuO4 revealed by electric pulses Bal Pokharel, Yuxin Wang, Jan J Jaroszynski, Takao Sasagawa, Dragana Popovic The dynamics of the charge-order domains has been investigated in La1.48Nd0.4Sr0.12CuO4, a prototypical stripe-ordered cuprate, using pulsed current injection. We first identify the regime in which nonthermal effects dominate over simple Joule heating and then demonstrate that, for small enough perturbation, pulsed current injection allows access to nonthermally induced resistive metastable states. The results are consistent with the pinning of the fluctuating charge order, with fluctuations being most pronounced at the charge-order onset temperature. The nonequilibrium effects are revealed only when the transition is approached from the charge-ordered phase. Our experiment establishes pulsed current injection as a viable and effective method for probing the charge-order dynamics in various other materials. |
Monday, March 14, 2022 3:36PM - 3:48PM |
D63.00004: Rotation of Unidirectional Charge Density Wave in ErTe3 in Response to Antisymmetric Strain Revealed by X-ray Diffraction Anisha G Singh, Maja D Bachmann, Joshua J Sanchez, Jong-Woo Kim, Philip J Ryan, Ian R Fisher We observed via x-ray diffraction (XRD) that application of anisotropic strain to an ErTe3 crystal can rotate the primary in-plane (here, the a/c plane) charge density wave (CDW) wavevector by 90o. ErTe3 belongs to the rare-earth tritelluride family, RTe3 (R=La-Pr, Sm, Gd-Tm), which are quasi-2D materials comprising nearly-square Te nets that exhibit unidirectional incommensurate CDW states. These materials are a model system to explore open questions regarding CDW formation and its interrelation with superconductivity. |
Monday, March 14, 2022 3:48PM - 4:00PM |
D63.00005: Optical Thermal Diffusivity Measurements in CsV3Sb5 Erik D Kountz, Aharon Kapitulnik, David Saykin, Claudia Felser CsV3Sb5 is a quasi-2D metal where the V atoms make a kagome lattice. It has a charge density wave (CDW) order and two time reversal symmetry breaking (TRSB) orders and is expected to have nontrivial Z2 band topology [1]. We use a photo-thermal microscope for high resolution thermal diffusivity and optical differential reflectivity measurements in CsV3Sb5 by measuring phase delay in local reflectivity. This is supplemented with specific heat and Kerr effect measurements. Our primary observation is at the CDW transition, a strong anomaly is observed in thermal diffusivity. Within within eight degrees of the CDW transition temperature, there diffusivity plummets by 40%. Resistivity measurement data is used to extract the electronic contribution of thermal conductivity. We will further discuss various contributions to the thermal conductivity and validity of the Wiedemann–Franz law law. |
Monday, March 14, 2022 4:00PM - 4:12PM |
D63.00006: Discovery of AV3Sb5 kagome superconductors and CsV3Sb5 Fermi surface mapping Brenden Ortiz, Samuel M Teicher, Linus Kautzsch, Paul M Sarte, Noah Ratcliffe, John W Harter, Jacob Ruff, Ram Seshadri, Stephen D Wilson Since our discovery of the AV3Sb5 (A: K, Rb Cs) family of kagome superconductors, the system has garnered significant attention within the condensed matter physics community, particularly due to the unique combination of nontrivial band topology, superconductivity, and signatures of electron correlations manifest via competing charge density wave order. Still, little is understood regarding the nature of the charge density wave (CDW) instability inherent to these compounds. To understand the impact of the CDW order on the electronic structure in these systems, we present quantum oscillation measurements on single crystals of CsV3Sb5. Our data provide direct evidence that the CDW invokes a substantial reconstruction of the Fermi surface pockets associated with the vanadium orbitals and the kagome lattice framework. Complementary diffraction measurements are further able to demonstrate that the CDW instability has a correlated phasing of distortions, and the average structure in the CDW state is proposed. |
Monday, March 14, 2022 4:12PM - 4:24PM |
D63.00007: Landau theory of charge density waves in AV3Sb5. Takamori Park, Mengxing Ye, Leon Balents In recent years, the AV3Sb5 (A=K, Cs, Rb) family of Kagome metals has attracted a lot of attention for its potential as a platform to study a plethora of interesting physics such as strong correlation, topology, van Hove singularities, superconductivity (SC), magnetism, and charge density waves (CDW). Motivated by experiments on the AV3Sb5 Kagome metals that indicate a CDW formation and a SC formation in the CDW state, we used a continuum model to study how interactions can induce density waves on a Kagome lattice. We found that the system can form a 3Q charge density wave but could also spontaneously break time-reversal symmetry by forming orbital currents. In addition, three-dimensional effects coming from interlayer coupling were identified as a possible mechanism to generate a three-dimensional density wave structure as well as C6 symmetry breaking. Lastly, the domain walls between different CDW states were considered and the possibility of time-reversal symmetry breaking caused by the formation of domain walls was studied. |
Monday, March 14, 2022 4:24PM - 4:36PM |
D63.00008: Raman scattering study of kagome metal AV3Sb5(A=Cs,Rb,K) Shangfei Wu, Brenden Ortiz, Stephen D Wilson, Hengxin Tan, Binghai Yan, Turan Birol, Girsh E Blumberg The kagome metal AV3Sb5 was recently discovered to host both superconductivity and charge density wave (CDW) order. Here, we use Raman scattering to probe the lattice dynamics of AV3Sb5. We identify several new A1g and E2g phonon modes related with V and Sb atoms as well as alkali atoms emerging in the CDW state. The symmetry decomposition analysis for these emerging modes indicates the C3 symmetry is preserved in the CDW phase. The limited number of new phonon modes indicates inversion symmetry is also preserved in the CDW phase. The detailed temperature evolution of these modes’ peak frequency, half-width-at-half-maximum, and integrated area support two successive phase transitions in CsV3Sb5: the first one with the primary-like order parameter appearing at TS = 94 K and the second one with secondary-like order parameter appearing at T∗ = 80 K. Moreover, the T-dependence of the integrated area for these modes show two type of behavior below TS: the low energy modes shows a plateau-like behavior below T∗ while the high energy modes monotonically increase below TS. These two types of behaviors below TS can be captured by a Landau free energy model incorporating the interplay between the primary-like and secondary-like order parameters. |
Monday, March 14, 2022 4:36PM - 4:48PM |
D63.00009: Rotation symmetry breaking in the normal state of a kagome superconductor KV3Sb5 Hong Li, He Zhao Recently discovered kagome superconductors AV3Sb5 (A=K, Rb, Cs) provide a fresh opportunity to realize and study correlation-driven electronic phenomena on a kagome lattice. The observation of a 2a0 by 2a0 charge density wave (CDW) in the normal state of all members of AV3Sb5 kagome family has generated an enormous amount of theoretical and experimental interest. We use low-temperature spectroscopic-imaging scanning tunneling microscopy to reveal a pronounced intensity anisotropy between different 2a0 CDW directions in KV3Sb5. In particular, by examining the strength of ordering wave vectors as a function of energy in Fourier transforms of differential conductance maps, we find that one of the CDW directions is distinctly different compared to the other two. This observation points towards an intrinsic rotation symmetry broken electronic ground state, where the symmetry is reduced from C6 to C2. Our experiments, combined with earlier observations of a stripe 4a0 charge ordering in CsV3Sb5, establish correlation-driven rotation symmetry breaking as a unifying feature of AV3Sb5 kagome superconductors. |
Monday, March 14, 2022 4:48PM - 5:00PM |
D63.00010: Possible Charge Instability in the Jellium Model with a Local Attractive Interaction Kun Chen We investigate the phase diagram of a three-dimensional uniform electron gas with a local attractive interaction in the intermediate density regime. We combine effective field theory with the numerical results obtained by diffusion quantum Monte Carlo and variational diagrammatic Monte Carlo methods. As the interaction increases, our analysis indicates an instability that could be related to an Overhauser-type charge density wave. |
Monday, March 14, 2022 5:00PM - 5:12PM |
D63.00011: The crucial role of SSH interactions in the bismuthate superconductors Bi1-xKxBiO3: A hybrid Monte Carlo study Benjamin Cohen-Stead, Richard T Scalettar, Kipton M Barros, Steven S Johnston Electron-phonon interactions can give rise to non-trivial emergent phenomena in quantum materials. For example, it is hypothesized that electron-phonon interactions are responsible for establishing the temperature-doping phase diagram of the bismuthate Bi1-xKxBiO3 (BKBO) family of high-temperature superconductors. The precise nature of the interaction, however, is debated. In this work, we study a three dimensional Su-Schrieffer-Heeger (SSH) model that we believe captures the most important features of the electron-phonon coupling mechanism in BKBO. Using model parameters based on ab initio calculations, we simulate our SSH model using a novel Hybrid Monte Carlo (HMC) method, allowing us to reach system sizes a full order of magnitude larger than previously possible. Focusing first on the half-filled case, we observe the formation of charge order with a critical temperature between 1150 - 1250 K. This result is in qualitative and approximate quantitative agreement with experimental results reporting analogous charge formation between 800 - 900 K in BKBO samples. We also present initial results showing enhanced pairing correlations upon doping, consistent with the emergence of high-temperature superconductivity in BKBO. |
Monday, March 14, 2022 5:12PM - 5:24PM |
D63.00012: Surface polarity-driven valence-ordered aperiodic crystalline structure Chi Ming Yim, Peter Wahl, Seunghyun Khim, Andrew Mackenzie, Olivia Armitage Chemical and electronic properties of surfaces and interfaces are important for many technologically relevant processes, including information processing where properties of interfacial electronic states are crucial for device performance, and chemical reactions where the catalytic properties of surface depend on types and densities of active nucleation sites. Aperiodic crystalline surfaces offer new opportunities due to their inherent inhomogeneity, resulting in electronic localization and properties vastly different from the surface of crystals with long-range order. Here, we demonstrate a new route to stabilization of an aperiodic crystalline structure at the surface of the single crystal palladium chromate. Stabilized by a valence disproportionation driven by the surface polarity, the surface reconstruction does not exhibit any translational periodicity, but consists of a space-filling aperiodic tiling. Measurement of the local density of states by tunneling spectroscopy reveals electronic localization in the surface layer. Our results indicate that aperiodic orders can form on top of a periodic solid, creating a new class of emergent orders. |
Monday, March 14, 2022 5:24PM - 5:36PM |
D63.00013: Competing orders in monolayer kagome metals AV3Sb5 Sun-Woo Kim, Hanbit Oh, Eun-Gook Moon, Youngkuk Kim Recently, there has been a surge of studies in layered kagome metals AV3Sb5, where A is an alkali metal atom, including K, Rb, and Cs, as a fertile platform to explore the electron correlation effects from van Hove singularity with nontrivial topology. Here, by using first-principles and mean-field calculations, we predict that the AV3Sb5 monolayer can be stable and a host of strong electronic correlations from enriched van Hove singularities. We find that in the monolayer stoichiometry enforces the symmetry lowering from D6h to D2h, which leads to the emergence of type-II van Hove singularities. The resulting electronic structure of the monolayer features a large electronic instability, which is relieved by the inverse-star-of-David charge density wave transition with nontrivial Z2 topology in the first-principles calculations. Correlation effects are further captured by mean-field analysis with the minimal tight-binding model. Intriguing competition physics between superconductivity and various charge density wave channels, including time-reversal symmetry broken one, is explored, demonstrating the interplay between band topology and electronic correlations. Our work suggests the existence of a new two-dimensional platform, which could help reveal the exotic van Hove physics enriched with symmetry engineering. |
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