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 S39: Electronic and Magnetic Properties of Correlated Oxide HeterostructuresFocus
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Sponsoring Units: DMP Chair: Kuntal Talit, University of California, Merced Room: Room 231 |
Thursday, March 9, 2023 8:00AM - 8:36AM |
S39.00001: Resonant tunneling driven metal-insulator transition in double quantum-well structures of strongly correlated oxide Invited Speaker: Hiroshi Kumigashira The metal-insulator transition (MIT), a fascinating phenomenon occurring in some strongly correlated materials, is of central interest in modern condensed-matter physics. Controlling the MIT by external stimuli is a key technological goal for applications in future electronic devices. However, the standard control by means of the field effect, which works extremely well for semiconductor transistors, faces severe difficulties when applied to the MIT [1]. Hence, a radically different approach is needed. In this talk, we report an MIT induced by resonant tunneling (RT) in double quantum well (QW) structures of strongly correlated oxides. In our structures, two layers of the strongly correlated conductive oxide SrVO3 (SVO) sandwich a barrier layer of the band insulator SrTiO3 (STO). The top QW is a marginal Mott-insulating SVO layer, while the bottom QW is a metallic SVO layer. As the top marginal Mott-insulating QW, we used a 2-ML SVO layer which can easily become a metal by applying a small perturbation [2,3]. As a counterpart, we used a 6-ML SVO for the bottom metallic QW layer, so as to induce the RT effect between two energetically close QW states [3,4]. Angle-resolved photoemission spectroscopy experiments revealed that the top QW layer became metallized when the thickness of the tunneling barrier layer was reduced. An analysis based on band structure calculations indicated that RT between the quantized states of the double QW induces the MIT. Our work opens avenues for realizing the RT-driven Mott transistor based on the wave-function engineering of strongly correlated electrons [5]. |
Thursday, March 9, 2023 8:36AM - 8:48AM |
S39.00002: Growth of PdCoO2 films with controlled termination by MBE and determination of their electronic structure by ARPES Qi Song, Jiaxin Sun, Christopher T Parzyck, Ludi Miao, Qing Xu, Felix V Hensling, Matthew R Barone, Cheng Hu, Jinkwon Kim, Brendan D Faeth, Hanjong Paik, Philip King, Kyle M Shen, Darrell G Schlom Utilizing the powerful combination of molecular-beam epitaxy (MBE) and angle-resolved photoemission spectroscopy (ARPES) we produce and study the effect of different terminating |
Thursday, March 9, 2023 8:48AM - 9:00AM |
S39.00003: Localized atomic vibrations in complex-oxide structures by monochromated EELS and theory Deliang Bao, Andrew O'Hara, Eric R Hoglund, Jordan Hachtel, Patrick Hopkins, James M Howe, Sokrates T Pantelides Atomic vibrations in crystals, namely phonons, are directly correlated to atomic arrangements and bonding and underlie a wide range of thermal, optical, and other properties. They especially reflect the structure and bonding at interfaces and defects. Here we combine density-functional-theory (DFT) calculations and monochromated electron-energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) to investigate atomic vibrations at interfaces and grain boundaries in complex oxides. Local symmetry (octahedral tilts) and phonons at interfaces differ markedly in short- and long-period SrTiO3/CaTiO3 superlattices and dominate properties in ultrashort periods1. At a low-angle grain boundary in SrTiO3, we directly correlate the structure, composition, and chemical bonding with atomic vibrations within the dislocation cores2. Theory and experiments provide mutual validation of results. Such quantification of atomic-scale vibrational properties is necessary to link macroscopic properties to atomic structure. |
Thursday, March 9, 2023 9:00AM - 9:12AM |
S39.00004: Strain Tunable Interface States at the LaAlO3/SrTiO3 Interface Mengke Ha, Qianyi Zhao, Chengyuan Huang, Zhenlan Chen, Zhiyuan Qin, Dawei Qiu, Qing Xiao, Changjian Ma, Danqing Liu, Guanglei Cheng The LaAlO3/SrTiO3 (LAO/STO) interface exhibits novel emergent phenomena, including metal-insulator transition, strong Rashaba spin-orbit coupling[1] (SOC), and electron pairing without superconductivity[2]. These properties can usually be modified by gating and temperature. Here we introduce an additional knob of mechanical strain through a homemade amplified strain cell, which is equipped with a high-precision capacitance sensor and can continuously tune the LAO/STO interface to a strain as large as 1.5% at 1.5K. Accordingly, we observe a large tunability on carrier density, mobility, spin-orbit coupling, and electron correlations. Further combined with a milli-Kelvin atomic force microscope, our platform is promising to explore strain tunable behaviors in real space and by quantum transport at oxide interfaces. |
Thursday, March 9, 2023 9:12AM - 9:24AM |
S39.00005: Fabrication of SrTiO3 (111) Oriented 2D Electron Gases and Gate Effect on Shubnikov de-Haas Oscillation Frequency Autumn Heltman, Ziqiao Wang, Jack Glaser, Shalini Kumari, Qi Li The discovery of 2D electron gases (2DEG) at SrTiO3 surfaces and interfaces has provided a robust platform to study many fundamental phenomena. In (111) oriented SrTiO3, Dirac bands and charge-ordered insulating phases have been predicted due to the honeycomb lattice formed by the top two layers of TiO6, similar to graphene. Previously, we have observed Shubnikov-de Haas oscillations to the lowest Landau level at relatively low magnetic field. Here, we report in-situ measurements of the conducing interface formation between amorphous oxide materials on (111) oriented SrTiO3. Initially, the surface is insulating, but after reaching a critical thickness, the interface becomes conducting and saturates at a larger thickness. At low temperatures, the sample has very high mobilities (>20,000 cm2V-1s-1) which is much higher than that of epitaxial interfaces with LaAlO3 grown at high temperature, possibly due to unstrained structure. Differences in the SdH oscillation frequencies were found in the sample with the same carrier density between virgin samples and those tuned with a back gate. Additionally, after reaching the quantum limit field the sample changes from a metallic state to an insulating state at higher magnetic fields. We are currently investigating the effect of both a back and a top gate on the Shubnikov de-Haas oscillation frequency and the high field insulating state, the result of which will be presented. |
Thursday, March 9, 2023 9:24AM - 9:36AM |
S39.00006: Control of valency and structural properties of [111] oriented oxide interfaces Thies Jansen, Nicolas Gauquelin, Alexander Brinkman Oxide thin films grown on [111] oriented substrates can give rise to new properties due to a different imposed crystal symmetry enforced by the growth direction. For example, a [111] oriented LaMnO3 bilayer is predicted to host topological states [1,2], which arises due to the combination of a buckled honeycomb lattice and spin orbit coupling [3]. We experimentally investigated these system by fabricating LaMnO3 bilayers and thin films on different substrates by means of pulsed laser deposition and characterize them by scanning transmission electron microscopy. We show that interface effects such as interdiffusion and the polar mismatch are important for the structural and electronic properties of bilayers in the [111] direction and can also give rise to unexpected oxygen distortions in thin films. Furthermore, the tunability of these properties by means of a buffer layer or strain is illustrated. |
Thursday, March 9, 2023 9:36AM - 9:48AM |
S39.00007: Cryogenic Piezoresponse Force Microscopy of LAO/STO nanostructures James P Keller, Joe Alboro, Patrick Irvin, Jeremy Levy LaAlO3 (LAO) and SrTiO3 (STO) nanostructures exhibit a myriad of electromechanical properties that offer great promise for application toward quantum computation and devices. Since most LAO/STO nanostructures, such as quantum dots (QDs) or single electron transistors (SETs), operate best at cryogenic temperatures1, low temperature SPM measurements are needed for probing LAO/STO devices. For our devices, we will use Piezoresponse force microscopy (PFM), a non-destructive measurement technique that can reveal “hidden” electronic properties2. By using PFM, we plan to simultaneously measure low temperature conductance and PFM, in hopes of better understanding the strain and carrier density relation of LAO/STO nanostructures, in order to achieve more control over LAO/STO based quantum devices, such as 2D QD arrays. |
Thursday, March 9, 2023 9:48AM - 10:00AM |
S39.00008: Enhancement of Charge Order by Heteroepitaxial Strain in Manganite/Cuprate Multilayers Chao C Zhang, Min Gu Kang, Riccardo Comin, John Y Wei We examine the role that epitaxial strain plays on the enhancement of the CuO2 charge order that was observed in superlattices of YBa2Cu3O7-δ (YBCO) and La2/3Ca1/3MnO3 (LCMO) [1]. Resonant x-ray scattering was used to measure the charge order onset temperature (TCO) in c-axis LCMO/YBCO/LCMO thin films at different YBCO thicknesses and oxygen contents. These trilayers were grown using pulsed laser-ablated deposition and characterized using x-ray diffraction and reflectometry, electrical transport, and x-ray absorption spectroscopy. We find higher TCO in trilayers with thinner YBCO layers even after accounting for strain-induced changes to its oxygen content . Our results indicate that the charge order in LCMO/YBCO multilayers can be enhanced by the epitaxial strain inherent in such heterostructures. |
Thursday, March 9, 2023 10:00AM - 10:12AM |
S39.00009: Utilizing Electrochemical Transformations and Enhancing Carrier Doping in Functional Oxides by Electrolyte Gating Hua Zhou, Wei Chen, Dillon D Fong, Hui Cao, Changjiang Liu The very high charge density induced by an electric double layer formed at the solid-liquid interface has recently been used to induced or "gate" exotic phase transitions, therefore electronic ground states of multifunctional oxides in the interfacial region, via the subtle interplay between electrostatic doping (electronic phenomena) and chemical redox effects (field-driven ionic motion) depending on field polarity and defect instability. In this talk, we will present two developing frontiers of ionic electrolyte gating within two contrasting mechanistic frameworks by illustrating most recent in-situ and real-time X-ray studies to deliver fundamental understanding of structural and chemical basis and their inherent links during gating on representative functional oxide heterostructures. In one end, we drive forward the limits of electrochemically emergent transformations by manipulating ionic defects during gating. For example, a combination of electronic and ionic doping processes across the interface of perovskite nickelate heterostructure (e.g. NdNiO3) by switching between positive and negative ionic gating voltages can be utilized in realizing electrochemical transistors. [1] Moreover, ionic gating process can induce dynamically manipulating oxygen octahedra-controlled properties in the complex oxides (e.g. WO3) for the design of highly responsive multifunctional materials. [2] In the other end, we create a new paradigm of highly efficient ionic gating toward sub-voltage operation regime (e.g. enhancing carrier doping but without defect generation across the interface) by designing redox actuatable poly-ionic-liquids. [3] |
Thursday, March 9, 2023 10:12AM - 10:24AM |
S39.00010: Combining ultrafast optical and x-ray spectroscopies for the study of emergent ferromagnetism at the LaNiO3/CaMnO3 interface Abigail M Derrico, Jay R Paudel, Martina Basini, Vivek Unikandanunni, Christoph Klewe, Padraic Shafer, Michael Terilli, Mikhail Kareev, Jak Chakhalian, Stefano Bonetti, Alexander Gray Epitaxial superlattices consisting of antiferromagnetic CaMnO3 and paramagnetic LaNiO3 exhibit emergent ferromagnetism that can be tuned by varying the thickness of individual layers. The thickness dependence of the interfacial magnetic moment can be attributed to the changes in the LaNiO3 layer, which undergoes a metal-insulator transition in the ultrathin (few-unit-cell) limit. Here, we use a combination of resonant soft x-ray reflectivity and time-resolved magneto-optic Kerr effect, optical reflectivity, and transmissivity spectroscopies of variable-thickness LaNiO3/CaMnO3 superlattices to disentangle multiple interrelated electronic and magnetic processes driven by ultrafast high-field THz electric-field pulses. Our new understanding of these phenomena makes the LaNiO3/CaMnO3 system a prime candidate for high-density spintronic devices wherein energy-efficient magnetic switching could be accomplished with electric fields or other external stimuli. |
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