一维反铁磁海森堡自旋链上spinon的安德森局域化最终报告

李世燕

摘 要：安德森局域化是物理学中的一个基本现象，最初是安德森提出在晶体中电子受到杂质散射由于散射路径的相干导致电导完全消失，这完全来源于电子的波动特性，后来在其他各种波，如，光、微波、超声波，甚至是冷原子体系中都观察到安德森局域化现象。在晶体中，除电子外，还可能存在各种各样的磁激发准粒子，但是对于这些磁性准粒子的安德森局域化研究几乎没有。我们测量了苯甲酸铜Cu（C6H5COO）2·3H2O这个一维反铁磁海森堡链单晶的极低温比热和热导率，发现一直到50 mK的極低温，spinon磁性准粒子对比热都有一个恒定的线性贡献项Cs/T，但是其热导率的线性贡献项ks/T只保持不变到300 mK。在300 mK以下，ks/T迅速减小，到100 mK以下就基本消失了。实验结果是spinon安德森局域化的一个较强的证据，为在凝聚态物理中研究安德森局域化现象开辟了一个新的窗口。

关键词：反铁磁自旋链 自旋子 热导率 安德森局域化

Abstract：Anderson localization is a general phenomenon of wave physics， which stems from the interference between multiple scattering paths. It was originally proposed for electrons in a crystal， but later was also observed for light， microwaves， ultrasound， and ultracold atoms. Actually， in a crystal， besides electrons there may exist other quasiparticles such as magnons and spinons. However the search for Anderson localization of these magnetic excitations is very rare so far. Here we report the first observation of spinon localization in copper benzoate， an ideal compound of spin-1/2 antiferromagnetic Heisenberg chain， by ultra-low-temperature thermal conductivity and specific heat measurements. We find that the spinons thermal conductivity ks manifests linear temperature dependence down to 300 mK. Below 300 mK， ks/T decreases rapidly and vanishes at about 100 mK， while the spinon specific heat Cs displays linear temperature dependence all the way down to 50 mK. This result is a clear evidence for Anderson localization of spinons in one-dimensional spin chain. Our finding opens a new window for studying such a fundamental phenomenon in condensed matter physics.

Key Words：Anitferromagnetic spin chain； Spinon； Thermal conductivity； Anderson localization

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