近日，加拿大舍布鲁克大学的A. Ataei&L. Taillefer及其研究团队取得一项新进展。经过不懈努力，他们揭示Sr₂IrO₄反铁磁相中杂质散射引起的声子手性。相关研究成果已于2024年1月30日在国际知名学术期刊《自然—物理学》上发表。

本文研究了在反铁磁绝缘体Sr₂IrO₄中加入铑杂质取代携带自旋的铱原子的影响，为声子杂质散射图提供了证据。研究人员发现添加小浓度的铑杂质会增加热霍尔电导率，但当添加足够的铑来抑制磁序时，热霍尔电导率会降低，直到几乎消失。相比之下，引入镧杂质来替代位于IrO₂平面之外的锶原子，其是磁性的所在，对热霍尔导电性的增强要小得多。研究结果表明，在反铁磁绝缘体Sr₂IrO₄中的热霍尔效应主要是由，嵌入在磁性环境中的杂质对声子的散射引起的。

据悉，热霍尔效应在越来越多的绝缘体中被观察到，其通常被归因于声子。然而，其潜在的机制在大多数情况下并不明确。目前，人们提出了两种主要假设：声子与自旋的耦合，或声子被杂质或缺陷散射。然而，这两种情况都缺乏系统的证据支持。

附：英文原文

Title: Phonon chirality from impurity scattering in the antiferromagnetic phase of Sr₂IrO₄

Author: Ataei, A., Grissonnanche, G., Boulanger, M.-E., Chen, L., Lefranois, ., Brouet, V., Taillefer, L.

Issue&Volume: 2024-01-30

Abstract: A thermal Hall effect occurs in an increasing number of insulators and is often attributed to phonons, but the underlying mechanism is not known in most cases. Two main scenarios have been proposed: either a coupling of phonons to spins or scattering of phonons by impurities or defects, but there is no systematic evidence to support either of them. Here we present evidence for the phonon impurity scattering picture by studying the effect of adding rhodium impurities to the antiferromagnetic insulator Sr₂IrO₄, substituting for the spin-carrying iridium atoms. We find that adding small concentrations of rhodium impurities increases the thermal Hall conductivity, but adding enough rhodium to suppress the magnetic order eventually decreases it until it nearly vanishes. In contrast, introducing lanthanum impurities that substitute for the strontium atoms, which lie outside the IrO₂ planes that are the seat of magnetism, produces a much smaller enhancement of the thermal Hall conductivity. We conclude that the thermal Hall effect in this material is caused by the scattering of phonons by impurities embedded within a magnetic environment.

DOI: 10.1038/s41567-024-02384-5

Source: https://www.nature.com/articles/s41567-024-02384-5