李世燕

摘 要：安德森局域化是物理學(xué)中的一個(gè)基本現(xiàn)象，最初是安德森提出在晶體中電子受到雜質(zhì)散射由于散射路徑的相干導(dǎo)致電導(dǎo)完全消失，這完全來(lái)源于電子的波動(dòng)特性，后來(lái)在其他各種波，如，光、微波、超聲波，甚至是冷原子體系中都觀察到安德森局域化現(xiàn)象。在晶體中，除電子外，還可能存在各種各樣的磁激發(fā)準(zhǔn)粒子，但是對(duì)于這些磁性準(zhǔn)粒子的安德森局域化研究幾乎沒(méi)有。我們測(cè)量了苯甲酸銅Cu（C6H5COO）2·3H2O這個(gè)一維反鐵磁海森堡鏈單晶的極低溫比熱和熱導(dǎo)率，發(fā)現(xiàn)一直到50 mK的極低溫，spinon磁性準(zhǔn)粒子對(duì)比熱都有一個(gè)恒定的線性貢獻(xiàn)項(xiàng)Cs/T，但是其熱導(dǎo)率的線性貢獻(xiàn)項(xiàng)ks/T只保持不變到300 mK。在300 mK以下，ks/T迅速減小，到100 mK以下就基本消失了。實(shí)驗(yàn)結(jié)果是spinon安德森局域化的一個(gè)較強(qiáng)的證據(jù)，為在凝聚態(tài)物理中研究安德森局域化現(xiàn)象開(kāi)辟了一個(gè)新的窗口。

關(guān)鍵詞：反鐵磁自旋鏈 自旋子 熱導(dǎo)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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