Pseudospin transport in the J_eff = 1/2 antiferromagnet Sr₂IrO₄

¹ Leibniz-Institute for Solid State and Materials Research, IFW-Dresden - 01069 Dresden, Germany
² Department of Physics and Department of Advanced Materials, University of Tokyo - Hongo 113-0033, Japan
³ Max-Planck-Institute for Solid State Research - 70569 Stuttgart, Germany
⁴ Center for Transport and Devices, TU Dresden - 01069 Dresden, Germany

^(a) c.hess@ifw-dresden.de

Received: 8 April 2016
Accepted: 17 June 2016

Abstract

Spin transport by itinerant electrons and collective excitations of localized spins with small relaxation rates is of eminent interest for both fundamental research and applications. Spin-orbit coupling (SOC) is not only considered a crucial origin for spin relaxation in spin transport, it recently emerged as the source of novel quantum phases such as topological insulators or SOC-induced Mott insulators with J_eff = 1/2 pseudospins. Here we show that emergent pseudospin excitations in Sr₂IrO₄ give rise to significant heat transport despite this compound being a strong SOC-induced Mott insulator. The analysis of the heat conductivity reveals boundary-limited relaxation of the pseudospin excitations at low temperature. However, the relaxation rate dramatically increases upon heating towards room temperature due to thermally activated scattering off phonons. The comparison of this result with findings for cuprate analogs with S = 1/2 spin excitations suggests a radically stronger coupling of the J_eff = 1/2 pseudospin excitations to the lattice.