Pressure-driven collapse of the relativistic electronic ground state in a honeycomb iridate

The electronic ground state in many iridate materials is described by a complex wave-function in which spin and orbital angular momenta are entangled due to relativistic spin-orbit coupling (SOC). Such a localized electronic state carries an effective total angular momentum of \(J_{eff}=1/2\). In ma...

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Bibliographic Details
Published in:arXiv.org 2018-03
Main Authors: Clancy, J P, Gretarsson, H, Sears, J A, Singh, Yogesh, Desgreniers, S, Mehlawat, Kavita, Layek, Samar, Gregory Kh Rozenberg, Ding, Yang, Upton, M H, Casa, D, Chen, N, Im, Junhyuck, Lee, Yongjae, Yadav, R, Hozoi, L, Efremov, D, van den Brink, J, Young-June, Kim
Format: Article
Language:English
Subjects:
Angular momentum
Benzene
Collapse
Conductivity
Coupling (molecular)
Crystal structure
Electron spin
Electron states
Electrons
Ground state
Honeycomb construction
Hydrostatic pressure
Molecular orbitals
Pressure
Relativism
Relativistic effects
Spin liquid
Spin-orbit interactions
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Summary:The electronic ground state in many iridate materials is described by a complex wave-function in which spin and orbital angular momenta are entangled due to relativistic spin-orbit coupling (SOC). Such a localized electronic state carries an effective total angular momentum of \(J_{eff}=1/2\). In materials with an edge-sharing octahedral crystal structure, such as the honeycomb iridates Li2IrO3 and Na2IrO3, these \(J_{eff}=1/2\) moments are expected to be coupled through a special bond-dependent magnetic interaction, which is a necessary condition for the realization of a Kitaev quantum spin liquid. However, this relativistic electron picture is challenged by an alternate description, in which itinerant electrons are confined to a benzene-like hexagon, keeping the system insulating despite the delocalized nature of the electrons. In this quasi-molecular orbital (QMO) picture, the honeycomb iridates are an unlikely choice for a Kitaev spin liquid. Here we show that the honeycomb iridate Li2IrO3 is best described by a \(J_{eff}=1/2\) state at ambient pressure, but crosses over into a QMO state under the application of small (~ 0.1 GPa) hydrostatic pressure. This result illustrates that the physics of iridates is extremely rich due to a delicate balance between electronic bandwidth, spin-orbit coupling, crystal field, and electron correlation.
ISSN:2331-8422
DOI:10.48550/arxiv.1803.04056