Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session J39: Invited Session: Transport, Superconductivity, and Magnetism at the LAO/STO Interface |
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Sponsoring Units: DCMP Chair: Allan H. MacDonald, University of Texas at Austin Room: Mile High Ballroom 2A-3A |
Tuesday, March 4, 2014 2:30PM - 3:06PM |
J39.00001: New spectroscopic measurements on localized charges at the interface Invited Speaker: Harold Y. Hwang |
Tuesday, March 4, 2014 3:06PM - 3:42PM |
J39.00002: Understanding oxide interfaces: From microscopic imaging to electronic phases Invited Speaker: Shahal Ilani In the last decade, the advent of complex oxide interfaces has unleashed a wealth of new possibilities to create materials with unexpected functionalities. A notable example is the two-dimensional electron system formed at the interface between LaAlO$_{\mathrm{3}}$ and SrTiO$_{\mathrm{3}}$ (LAO/STO), which exhibits ferromagnetism, superconductivity, and a wide range of unique magneto-transport properties. A key challenge is to find the microscopic mechanisms that underlie these emergent phenomena. While there is a growing understanding that these phenomena might reflect rich structures at the micro-scale, experimental progress toward microscopic imaging of this system has been so far rather limited due to the buried nature of its interface. In this talk I will discuss our experiments that study this system on microscopic and macroscopic scales. Using a newly-developed nanotube-based scanning electrometer we image on the nanoscale the electrostatics and mechanics of this buried interface. We reveal the dynamics of structural domains in STO, their role in generating the contested anomalous piezoelectricity of this substrate, and their direct effects on the physics of the interface electrons. Using macroscopic magneto-transport experiments we demonstrate that a universal Lifshitz transition between the population of d-orbitals with different symmetries underlies many of the transport phenomena observed to date. We further show that the interactions between the itinerant electrons and localized spins leads to an unusual, gate-tunable magnetic phase diagram. These measurements highlight the unique physical settings that can be realized within this new class of low dimensional systems. [Preview Abstract] |
Tuesday, March 4, 2014 3:42PM - 4:18PM |
J39.00003: Chiral magnetism at oxide interfaces Invited Speaker: Mohit Randeria There are tantalizing hints of magnetism at the n-type LaAlO$_3$/SrTiO$_3$ interface, but the experimental evidence remains controversial in view of some of the differences between different samples and probes. I will argue that if magnetism exists at interfaces, symmetry arguments imply chiral interactions [1] that lead to a spiral ground state in zero external field and skyrmion crystals for $H \neq 0$. I will next present a microscopic model that provides a possible mechanism for the formation of local moments. I will show that the coupling of these moments to itinerant electrons leads to ferromagnetic double exchange together with Dzyaloshinskii-Moriya (DM) interactions and an easy-plane ``compass'' anisotropy, which arise from Rashba spin-orbit coupling (SOC) due to the lack of inversion symmetry at the interface. The compass term, often ignored in the literature on chiral magnetism, is shown to play a crucial role in determining the magnetic ground state. I will compare our results with existing torque magnetometry data on LAO/STO and try to reconcile it with scanning SQUID magnetometry. Finally, I will present the phase diagram in a field and show that easy-plane anisotropy stabilizes an unexpectedly large skyrmion crystal phase and describe its properties. (Work done in collaboration with Sumilan Banerjee, Onur Erten, Daniel Kestner and James Rowland). \\[4pt] [1] S. Banerjee, O. Erten and M. Randeria, Nature Physics 9, 626 (2013). [Preview Abstract] |
Tuesday, March 4, 2014 4:18PM - 4:54PM |
J39.00004: Magnetism, Superconductivity and Pseudogap at the LaAlO$_{3}$-SrTiO$_{3}$ Interface Invited Speaker: Jochen Mannhart The electron liquid at the LaAlO$_{3}$-SrTiO$_{3}$ interface is a two-dimensional superconductor and simultaneously displays magnetic order. To experimentally explore the fundamental properties of this state, we developed a planar tunnel junction technology that allows to measure the spectral density-of-states of the superconducting liquid while its carrier density can be altered by the electric-field effect. These studies yield surprising results, as key features of the superconducting electron liquid at the LaAlO$_{3}$-SrTiO$_{3}$ interface are found to be analogous to features deemed characteristic for the high-$T_{\mathrm{c}}$ cuprates. This work was performed in collaboration with C. Richter, H. Boschker, W. Dietsche, E. Fillis-Tsirakis, R. Jany, F. Loder, L.F. Kourkoutis, D.A. Muller, J.R. Kirtley, and C.W. Schneider. [Preview Abstract] |
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