Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Z29: Electronic Orders and Emergent Behavior in Complex Oxides: A Synchrotron ViewInvited Live Streamed
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Sponsoring Units: GMAG DMP DCOMP DCMP Chair: Laurent Chapon, Advanced Photon Source Room: McCormick Place W-190B |
Friday, March 18, 2022 11:30AM - 12:06PM |
Z29.00001: Spin excitations in quantum spin liquid materials Invited Speaker: Young S Lee Quantum spin liquids are novel states of matter possessing long range quantum entanglement. An important experimental signature of such a state would be spin excitations that are characterized by fractionalized quantum numbers. For the kagome quantum spin liquid candidate materials Zn-barlowite and herbertsmithite, inelastic scattering and other measurements have provided evidence for the presence of fractionalized spinon excitations. To facilitate the interpretation of the data, it is important to determine the role that impurities and/or structural imperfections might play in the spin excitation spectrum. We discuss recent experimental probes of the excitations and effects of impurities in these materials, including x-ray spectroscopy and resonant inelastic x-ray scatttering measurements in our powder and single crystal samples. |
Friday, March 18, 2022 12:06PM - 12:42PM |
Z29.00002: A journey across excitations in functional quantum materials using resonant inelastic x-ray scattering Invited Speaker: Valentina Bisogni The past years have witnessed an increasing interest in the field of quantum materials (QM), not only thanks to their fascinating behaviour as a macroscopic manifestation of quantum mechanics, but also for the opportunities that these materials offer in terms of ‘emergence’ of functional properties (high-temperature superconductivity, quantum Hall effect, giant magnetoelectric effect, etc...). Understanding the physics behind quantum materials is thus a primary goal of condensed matter physics, both from a fundamental as well from an applied perspective, with the ultimate scope of gaining control of QM properties towards the next generation of electronics. |
Friday, March 18, 2022 12:42PM - 1:18PM |
Z29.00003: Near-field optical studies to untangle electronic ordering in complex oxides Invited Speaker: Mengkun Liu Correlated quantum materials especially transition metal oxide thin films and bulk crystals can host intricating phase textures at the nanoscale. This includes the recently discovered moiré-type phase separations or current induced metal-insulator-metal stripes in manganites, ruthenates, and vanadium oxides. Infrared (~10-103 meV) and terahertz (~1-10 meV) near-field nano-optics allows us to directly image those novel mesoscopic phases and study their low energy spectrum with 10 nm spatial resolution. To quantitatively resolve the phase properties, we introduced machine learning methods to predict the optical dielectric functions directly from raw imaging and spectroscopy data. Via a combination of the state-of-the-art broadband infrared light sources, improved capabilities in the scanning probe techniques, and new types of data analysis and acquisition toolboxes, we set the stage for future nanoscopic investigations of low energy electron, phonon, and spin dynamics in complex oxides systems. |
Friday, March 18, 2022 1:18PM - 1:54PM |
Z29.00004: Dynamics of frustrated antiferromagnets studied using pulsed magnetic fields and X-ray photon correlation spectroscopy Invited Speaker: Vivien Zapf Frustration in antiferromagnets can lead to surprising dynamic behavior as well as spatial inhomogeneities. We study these using a combination of pulsed magnetic fields with different timescales, resonant coherent X-ray measurements, and Monte Carlo simulations. Here I will discuss two compounds, Lu2CoMnO6 and Ca3Co2O6, in which nearest-neighbor frustration gives rise to a version of the axial next-nearest neighbor Ising model (ANNNI). This model predicts a fractal (infinite) set of phases with incommensurate wave vectors that are separated by first-order phase boundaries. This complexity results from a simple frustration condition between nearest- and next-nearest-neighbor interactions along a chain of Ising spins. The incommensurate wave vector slides with temperature, finally giving rise to a commensurate ground state at the lowest temperatures. Strong dynamics and inhomogeneities of the antiferromagnetic order have been observed in both compounds. I will talk about X-ray photon correlation spectroscopy (XPCS) results in Lu2CoMnO6 that show unusual dynamics of antiferromagnetic fluctuations as a function of temperature that match the predictions of the ANNNI model. I will also talk about pulsed magnetic field results in Ca3Co2O6 and finally DC annealing experiments designed to elucidate the metastable magnetization steps and reach the ground state of this compound. |
Friday, March 18, 2022 1:54PM - 2:30PM |
Z29.00005: Charge and spin stripe formation and dynamics in nickelates Invited Speaker: Yao Shen Various nickelates, which have long been viewed as potential analogs to cuprate superconductors, host spin and charge stripe orders. Remarkably, superconductivity was discovered in the square-planar nickelate family, making the characterization and understanding of stripe orders in nickelates increasingly appealing. Here we use resonant x-ray photon correlation spectroscopy to study the temporal stability and domain memory of the stripe orders in La2−xSrxNiO4+δ [1]. Temperature dependent fluctuations are observed for both the charge and spin stripes. Notably, charge order shows robust domain memory with thermal cycling up to 250 K, far above the ordering temperature, while the spin stripe speckle pattern loses reproducibility once the sample is warmed across the transition temperature. We extend our discussion to the square-planar La4Ni3O8, in which similar diagonal charge and spin stripe orders form at low temperature, and make further comparison with the cuprates [2, 3]. |
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