Quantitative calculation of magnon transport properties of insulators

我已经为原子自旋动力学实现了一个量子恒温器。在简单系统中，我通过与可解析推导的结果进行比较，在复杂系统中，我通过与实验进行比较，严格地检验了它的正确性。这一结果的手稿正处于准备提交的最后阶段。本文成功地计算了钇铁石榴石（yyg）复合磁性绝缘体中的磁振子输运性质。这包括磁振子自旋电导率和磁振子热电导率。这项工作要求量子恒温器在所有温度下都能得到正确的结果。磁振子自旋电导率与实验测量结果一致，但热电导率在较高温度下存在差异，这可能是由于缺陷或声子造成的。这部作品的手稿将很快完成并提交出版。我还研究了反铁磁绝缘体中的磁振子输运，特别是Cr2O3，与Eiji saiitoh教授（Tohoku）和约翰内斯古腾堡大学（Johannes Gutenberg University, Mainz）的理论家合作。在YIG/Cr2O3/Pt器件中，Cr2O3可用于开关自旋电流。这项研究发表在《自然材料》杂志上。Cr2O3中各向异性的异常温度依赖性对此很重要，我目前正在准备一份手稿，其中我的计算表明该材料中的偶极子各向异性具有异常行为。

I have implemented a quantum thermostat for atomistic spin dynamics. I have rigorously checked its correctness in simple systems by comparison with analytically derivable results and in complex systems by comparing to experiments. The manuscript for this result is in the final stages of preparation for submission.I have succeeded in calculating magnon transport properties in the complex magnetic insulator Yttrium Iron Garnet (YIG). This includes the magnon spin conductivity and the magnon heat conductivity. This work required the quantum thermostat to achieve correct results at all temperatures. The magnon spin conductivity shows excellent agreement with experimental measurements but the heat conductivity shows a difference at higher temperature which may be due to defects or phonons. The manuscript of this work will soon be written and submitted for publication.I have also investigated magnon transport in antiferromagnetic insulators, notably Cr2O3, in collaboration with the experimental group of Prof. Eiji Saitoh (Tohoku) and theorists at the Johannes Gutenberg University, Mainz. In YIG/Cr2O3/Pt devices the Cr2O3 can be used to switch spin currents on and off. This work was published in Nature Materials. The unusual temperature dependence of anisotropy in Cr2O3 is important for this and I am currently preparing a manuscript where my calculations show the dipole anisotropy in this material has an anomalous behaviour.