Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session A63: Experiments on Correlated Electron SystemsRecordings Available
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Sponsoring Units: DCMP Chair: Arneil Reyes, FSU-NHMFL Room: Hyatt Regency Hotel -Grant Park A |
Monday, March 14, 2022 8:00AM - 8:12AM |
A63.00001: Low Temperature Heat Capacity Measurements of KYbSe2 Andrew J Woods, Sangyun Lee, Allen O Scheie, Cristian Batista, David A Tennant, Roman Movshovich Quantum spin liquids (QSLs) are a proposed state of matter characterized by fractionalized quasiparticle excitations, quantum entanglement and a lack of long range magnetic order. QSLs have so far evaded definitive experimental observation. There has been significant study of Yb3+ based materials as QSL candidates due to the Yb3+ S = ½ state, but thus far these studies have not provided an unambiguous proof of a QSL. Here we investigate the Yb3+ delafossite material KYbSe2, which is a promising QSL candidate. |
Monday, March 14, 2022 8:12AM - 8:24AM |
A63.00002: Phase transitions in nanoscale vanadium pentoxide Nicholas C Jerla, George Agbeworvi, Sarbajit Banerjee, Sambandamurthy Ganapathy Ternary vanadium oxide bronzes (MxV2O5) obtained from intercalation of metal ions (M = Pb, Hg, Cu, Ag) exhibit a variety of structural and electronic properties such as charge ordering and metal-insulator phase transitions. The addition of these cations within the vanadium oxide network can induce strongly correlated behavior that can be probed and controlled by external parameters such as temperature, electric, and magnetic fields. Transport measurements in conjunction with resistance noise spectroscopy are performed on nanowires of vanadium pentoxide crystals. An abrupt, repeatable change from a low to a high conducting state is observed in our electrical measurements pointing to a subtle interplay among various degrees of freedom. Understanding the mechanisms behind the transitions yield insights into the role of electron correlations in these systems and how to modulate them for applications. |
Monday, March 14, 2022 8:24AM - 8:36AM |
A63.00003: Nanotextured dynamics of a light-induced phase transition in VO2 Aaron Sternbach, Frank Ruta, Yin Shi, Tetiana Slusar, Jacob S Schalch, Guangwu Duan, Alexander S McLeod, Xin Zhang, Mengkun Liu, Andrew J Millis, Hyun-Tak Kim, Long-Qing Chen, Richard D Averitt, Dmitri N Basov Light is a powerful tool, capable of inducing phase transitions in quantum materials on-demand. Light-induced states can, however, exhibit complex phase separation at the nanoscale. Here, we investigate transient nanotextured heterogeneity in vanadium dioxide (VO2) thin films during a light-induced insulator-to-metal transition (IMT). Room temperature, steady-state, phonon enhanced nano-optical contrast reveals preexisting “hidden” disorder. The observed contrast is associated with inequivalent twin domain structures. Upon thermal or optical initiation of the IMT coexisting metallic and insulating regions are observed. Correlations between the transient and steady-state nano-optical textures reveal that heterogeneous nucleation is partially anchored to twin domain interfaces and grain boundaries. Ultrafast nanoscopic dynamics enable quantification of the growth rate and bound the nucleation rate. Finally, we deterministically anchor photo-induced nucleation to predefined nanoscopic regions by locally enhancing the electric field of pump radiation using nano-antennas and monitor the on-demand emergent metallicity in space and time. |
Monday, March 14, 2022 8:36AM - 8:48AM |
A63.00004: Observation and Strain Control of Electronic Phase Transitions in a Quasi-1D Chalcogenide BaTiS3 Huandong Chen, Batyr Ilyas, Boyang Zhao, Emre Ergecen, Joshua C Mutch, Guodong Ren, Bryan C Chakoumakos, Simon Teat, Rohan Mishra, Jiun-Haw Chu, Nuh Gedik, Jayakanth Ravichandran BaTiS3 is a member of ternary transition metal chalcogenides with hexagonal symmetry1. For many years this material has been considered a trivial small bandgap semiconductor with no electron or lattice instabilities due to the nominally unoccupied Ti 3d orbitals2. Here, we report the first experimental observation of a series of electronic phase transitions in single crystals of BaTiS3 from electrical transport measurements. Two different phase transitions are identified from abrupt hysteric jumps in electrical resistance at 150-190 K and 245-255 K, respectively, which are further supported by complementary characterizations including synchrotron X-ray diffraction, optical spectroscopies and DFT calculations. These transitions are sensitive to external strain fields. By controlling the thermal strain between the crystal and embedding medium, we can tune the transitions systematically. Different responses of the two transitions to extrinsic strain field further hint of their distinct origins. |
Monday, March 14, 2022 8:48AM - 9:00AM |
A63.00005: Anomalous Structural Phase Transition in Ferromagnetic SrCoO2.875 Amani S Jayakody, William Hines, Sanjeev K Nayak, Saul H Lapidus, Milinda Abeykoon, Joseph I Budnick, Jianhang Shi, Menka Jain, Barrett O Wells The concept of electronic phase separation explains several unusual magnetic and electronic properties of doped perovskite oxides such as cuprates, manganites, and cobaltites. Strontium cobalt oxide with varying oxygen concentration (SrCoO3-y, 0 < y < 0.125) is one of the systems which shows magnetic phase separation for intermediate oxygen values. The end points are SrCoO2.875 which is ferromagnetic with Tc = 220 K and SrCoO3 which is also ferromagnetic but with Tc = 280 K. Samples with intermediate values of oxygen concentration show two phase magnetic behavior between these values, but a single average structure as determined by diffraction. We undertook high resolution x-ray powder diffraction measurements to better understand the underlying structure. SrCoO3 remains in the simple cubic perovskite structure from 10-300 K. SrCoO2.875 has a much more complicated structure. At room temperature it is tetragonal with an expanded unit cell. Upon cooling, the structure appears to undergo a second order transition to a cubic phase. This is extremely unusual and the opposite of typical structural transitions which proceed to lower symmetry structures at lower temperatures. We present our structural studies and supporting DFT calculations of the energetics of the phases identified. |
Monday, March 14, 2022 9:00AM - 9:12AM |
A63.00006: Influence of plastic deformation on the structural and electronic properties of SrTiO3 and KTaO3 Issam Khayr, Sajna Hameed, Damjan Pelc, Matthew J Krogstad, Raymond Osborn, Yaohua Liu, Feng Ye, Martin Greven Strontium titanate (SrTiO3, STO) and potassium tantalate (KTaO3, KTO) are quantum paraelectrics with cubic perovskite structures at room temperature. These two materials serve as excellent candidates for plastic deformation because of their outstanding room temperature ductility. Recent work on plastically-deformed STO has shown an enhancement of the superconducting transition temperature and the emergence of local ferroelectricity near strain-induced self-organized dislocation walls [1]. Building on this study, we investigate the influence of compressive plastic deformation on the cubic-to-tetragonal structural transition in STO and on the structural and electronic properties of KTO. |
Monday, March 14, 2022 9:12AM - 9:24AM |
A63.00007: Effects of Temperature and Pressure on Structural Transformations in CuInP2S6 and CuInP2S6-In4/3P2S6 heterostructures Michael A Susner, Rahul Rao, Benjamin S Conner, David S Parker CuInP2S6 is a van der Waals gapped material with a high transition temperature (TC=315) under ambient conditions. Recent work has shown that this material is useful for a variety of applications (e.g. ultrasound transducers, frequency conversion, ferroelectric capacitor, ferroelectric field effect transducer, etc). Under pressure, CuInP2S6 sees an increase in its ferroelectric Curie temperature, in contrast to most ferroelectric materials, due to the fact that its unit cell decreases in the ferroelectric state. Additionally, at higher pressures (> 4.0 GPa) the layered structure of CuInP2S6 transforms into one with a more 3D nature- depending on the pressure applied, the stacking first changes to a higher symmetry monoclinic and then further transforms to a trigonal system which, in similar FePS3 and FePSe3 materials results in interesting changes in the band structure enabling changes from semiconductor/insulator to conductor. We have undertaken a dual Raman and diffraction study to characterize the ferroelectric transition as a function of pressure and temperature in CuInP2S6. We have also worked to study the effects of pressure on the electronic structure of the material through (P,T) investigations. Finally, we have incorporated ab initio theoretical investigations of CuInP2S6 to explain the evolution of the structure-property relationships in this system. |
Monday, March 14, 2022 9:24AM - 9:36AM |
A63.00008: Order-disorder vs Displacive structural phase transitions in (CaxSr1-x)3Rh4Sn13 Puspa Upreti, Matthew J Krogstad, Charlotte Haley, Mihai Anitescu, Vishwas Rao, Lekhanath Poudel, Omar Chmaissem, Stephan Rosenkranz, Raymond Osborn A three-dimensional quasi-skutterudite compound (CaxSr1-x)3Rh4Sn13 undergoes a second-order structural phase transitions from a simple cubic I phase structure (Pm-3n) to a body-centered cubic I’ superstructure (I-43d) but the nature of transition either displacive or order-disorder has not been categorized yet. To distinguish between these two characters, local order parameter fluctuations were estimated by transforming the x-ray diffuse scattering data of single crystal (CaxSr1-x)3Rh4Sn13 with x=0.0, 0.1, 0.6, 0.65, 0.7, 0.9 to a real space producing a three-dimensional pair distribution function using a new ‘Gaussian tiling’ approach rather than a conventional ‘punch and fill’ method. The 3D-ΔPDF analysis shows that the amplitudes of local atomic displacements are independent of both temperature and doping, a much clearer signature of order-disorder transitions than possible by other methods. |
Monday, March 14, 2022 9:36AM - 9:48AM |
A63.00009: Local Structure Influence on Multiferroic Properties Braedon C Jones, Benjamin A Frandsen, Omar Chmaissem The multiferroic system (Sr,Ba)(Mn,Ti)O3 is a promising material for multiferroic applications |
Monday, March 14, 2022 9:48AM - 10:00AM |
A63.00010: Optical properties of the layered phosphide EuCd2P2 Christopher C Homes, Zhi-Cheng Wang, Kyle Fruhling, Fazel Tafti The temperature dependence of the optical properties of the layered material EuCd2P2 have been determined over a wide frequency range for light polarized in the planes. At room temperature, the low-energy optical conductivity reveals two infrared-active Eu vibrational modes (one weak, the other very strong) superimposed on a weak electronic background, with σ1(ω→0) ~30 Ω-1cm-1. At high temperature the optical conductivity can be reproduced reasonably well using a Drude-Lorentz model for the dielectric function, yielding an estimate for the Drude plasma frequency ωp,D ~1700 cm-1 and scattering rate 1/τD ~1600 cm-1. In the far-infrared region the conductivity increases with decreasing temperature until just above the magnetic transition at TN ~11 K, where it decreases dramatically, but recovers by 5 K, in good agreement with transport measurements [1]. It is proposed that the decrease in optical conductivity is due to carrier localization driven by strong antiferromagnetic fluctuations. |
Monday, March 14, 2022 10:00AM - 10:12AM |
A63.00011: Imaging Hydrodynamic Electrons Flowing Without a Landauer-Sharvin Resistance Chandan Kumar, John Birkbeck, Joseph Sulpizio, David Perello, Takashi Taniguchi, Kenji Watanabe, Oren Reuven, Thomas Scaffidi, Ady Stern, Andre K Geim, Shahal Ilani Electrical resistance usually originates from lattice imperfections. However, even a perfect lattice has a fundamental resistance limit, given by the Landauer conductance of its discrete modes. This resistance, shown by Sharvin to appear at the contacts of electronic devices, sets the ultimate conduction limit of non-interacting electrons. Recent years have seen growing evidence of hydrodynamic electronic phenomena, prompting recent theories to ask whether an electronic fluid can radically break the fundamental Landauer-Sharvin limit. Here, we use single-electron-transistor imaging of electronic flows in high-mobility graphene Corbino disk devices to answer this question. First, by imaging ballistic flows at low temperatures, we observe a Landauer-Sharvin resistance that does not appear at the contacts but is instead distributed throughout the bulk. This underpins the phase-space origin of this resistance - as emerging from spatial gradients in the number of conduction modes. At elevated temperatures, we identify and account for the contribution of electron-phonon scattering, thus revealing the purely hydrodynamic flow. Strikingly, we find that electron hydrodynamics eliminates the bulk Landauer-Sharvin resistance. Finally, by imaging spiraling magneto-hydrodynamic Corbino flows we reveal the key emergent length-scale predicted by hydrodynamic theories – the Gurzhi length. These observations demonstrate that electronic fluids can dramatically transcend the limitations of ballistic electrons, with important implications for fundamental science and future technologies. |
Monday, March 14, 2022 10:12AM - 10:24AM |
A63.00012: Unusual Power Law Frequency-dependence of THz Complex Conductivity of Disordered LaxEu1-xNiO3/LSAT (100) Thin Films Gulloo L Prajapati, Sarmistha Das, Dhanvir S Rana The presence of disorder has a strong influence on the phase diagram of transition metal oxides. Here, we present low energy carrier dynamics of quench disordered LaxEu1-xNiO3/LSAT (100) thin films. While DC transport probes only the overall macroscopic electronic state of the films i.e., insulating state, metal-insulator transition and complete metallic state, for x = 0.25, 0.50 and 0.75, respectively in the temperature range of 2-300 K, the terahertz spectroscopy provides much deeper insights about the microscopic states and their responses at low energy (~meV) range. For x = 0.50, the complex conductivity is dominated by Drude-Smith type response while for x = 0.25 and 0.75, the conductivity exhibits strong power-law frequency dependence. The power-law frequency dependence of the conductivity is most for x = 0.25 i.e., for insulating film. The Drude and Drude-Smith type carrier transports in strongly correlated materials are very common however, the power-law frequency dependence of the conductivity is very rare and is a typical characteristics of non-metallic disordered systems. Thus, the power-law frequency dependence of the conductivity of nickelates reveals its strong behavioral resemblance with non-metallic disordered systems. Conversely, it suggests that the disorder-induced electronic inhomogeneity acts as random free energy barriers other than the scattering center where free charge carriers get accumulated. On increasing THz frequency, these accumulated charge carriers contribute to additional conductivity, thus, overall conductivity increases. |
Monday, March 14, 2022 10:24AM - 10:36AM |
A63.00013: Spectroscopy of the Wigner crystal on helium and color center spectroscopy Mark I Dykman, Alexei D Chepelianskii, Denis Konastantinov Electrons on the helium surface form a strongly correlated nondegenerate liquid or a Wigner crystal. In the both phases they display sharp resonant absorption lines related to the transitions between the subbands of quantized motion transverse to the helium surface. A magnetic field parallel to the surface strongly affects the absorption spectrum. We show that the effect results from admixing the intersubband transitions to the in-plane quantum dynamics of the many-electron system. Our many-electron theory of the interband absorption spectra and the experimental observations are in full quantitative agreement, with no adjustable parameters. The results refer to a broad range of the electron densities, temperature, and the coupling strength of the in-plane and out-of-plane motions. The in-plane motion was quantized by the magnetic field normal to the surface, which is advantageous for revealing nontrivial aspects of the many-electron dynamics. The admixture of the in-plane excitations to the electron transition is similar to the admixing of phonons to electron transitions in color centers. The system provides a unique setting where both the effective coupling strength and the spectrum of elementary excitations coupled to the electron transition can be varied in situ by varying the in-plane and out-of-plane magnetic fields. |
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