Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X50: Orbital Degeneracy Breaking and Emergent Local Symmetry in Transition Metal CompoundsInvited Live
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Sponsoring Units: DCMP Chair: Simon Kimber, University of Bourgogne |
Friday, March 19, 2021 8:00AM - 8:36AM Live |
X50.00001: Orbital molecules in oxides Invited Speaker: Paul Attfield Orbital molecules are weakly bonded clusters of transition metal ions within an orbitally ordered solid.[i] The importance of these states has become apparent in recent years following the discovery of ‘trimeron’ orbital molecules in the ground state of magnetite (Fe3O4).[ii] Determination of the full superstructure below the famous Verwey transition at 125 K showed that Fe2+/Fe3+ charge ordering occurs with a pronounced orbital ordering of Fe2+ states that leads to localization of electrons in the linear, three-Fe trimerons. The same complex electronic order is observed in a natural magnetite sample.[iii] Site-selective doping of ordered charge states in magnetite has recently been observed.[iv] Electronic phase separation driven by trimeron formation has recently been reported in CaFe3O5.[v] |
Friday, March 19, 2021 8:36AM - 9:12AM Live |
X50.00002: Interplay between Jahn-Teller effect and spin-orbit coupling Invited Speaker: Sergey Streltsov The Jahn-Teller effect is one of the most fundamental phenomena important not only for physics, but also for chemistry and material science. Solving the Jahn-Teller problem and taking into account strong electron correlations we show that quantum entanglement of the spin and orbital degrees of freedom via spin--orbit coupling strongly affects this effect. Depending on the number of d electrons it may quench (electronic configurations t2g2, t2g4, and t2g5), partially suppress (t2g1) or in contrast induce (t2g3) Jahn-Teller distortions. Moreover, in certain situations, interplay between the Jahn-Teller effect and spin--orbit coupling promotes formation of the "Mexican hat" energy surface facilitating various quantum phenomena [1]. |
Friday, March 19, 2021 9:12AM - 9:48AM Live |
X50.00003: Local Orbital Degeneracy Lifting as a Precursor to Orbital-Selective Peierls Transitions Invited Speaker: Emil Bozin Fundamental electronic principles underlying all transition metal compounds are the symmetry and filling of the d-electron orbitals and the influence of this filling on structural configurations and responses. Here we use a sensitive local structural technique, x-ray atomic pair distribution function analysis, to reveal the presence of fluctuating local-structural distortions at high temperature of several transition metal based quantum materials exhibiting orbital-selective groud states. We show that this hitherto overlooked fluctuating symmetry-lowering is electronic in origin and will modify the energy-level spectrum and electronic and magnetic properties. The explanation is a local, spatio-temporally fluctuating, orbital degeneracy lifted state, a precur to electronic phenomena observed at low temperature. We demonstrate that such local orbital states come in many flavors (e.g. engaging single [1,2] or multiple d orbitals [3]), and that they are likely to exist both in the proximity to itinerant-to-localized crossover [1,3] and deep in the Mott insulating regime where charge fluctuations are suppressed [4]. These observations suggest that such precursor states are likely to be widespread amongst diverse classes of partially filled nominally degenerate d-electron systems, with potentially broad implications for our understanding of their properties. |
Friday, March 19, 2021 9:48AM - 10:24AM Live |
X50.00004: Hajime Ishikawa Invited Talk Invited Speaker: Hajime Ishikawa TBD |
Friday, March 19, 2021 10:24AM - 11:00AM Live |
X50.00005: Scattering Signatures of Bond-Dependent Magnetic Interactions Invited Speaker: Joseph Paddison Bond-dependent interactions can generate exotic topological states such as Kitaev spin liquids [1]. Such states have potential applications for topological quantum computation, and are of fundamental interest because they can show entangled ground states whose excitations have fractional quantum numbers [2]. |
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