arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1504.01259cond-mat.str-el
收藏

Kitaev模型中量子自旋的热分馏:$T$ -线性specific heat和Majorana费米子的相干输运

Thermal fractionalization of quantum spins in a Kitaev model: $T$-linear specific heat and coherent transport of Majorana fermions

Joji Nasu, Masafumi Udagawa, Yukitoshi Motome

摘要:

从量子$S=1/2$自旋分解为巡游和定域两种Majorana费米子的观点出发,用量子蒙特卡罗模拟研究了蜂窝晶格上Kitaev模型的$T$性质.在这个系统中,熵是连续释放在两个良好分离的$T$尺度,作为一个明确的指示的热分馏。我们发现由巡游马约拉纳费米子驱动的高$T$交叉与最近邻自旋关联的发展密切相关。另一方面,低- $T$交叉起源于局部马约拉纳费米子组成的通量的热涨落,从而对巡游马约拉纳费米子的光谱产生了显着的干扰。因此,在中间- $T$范围之间的两个交叉,系统表现出$T$ -线性行为的比热和相干传输的马约拉纳费米子,这是意想不到的狄拉克半金属光谱在低- $T$限制。我们还表明,通量波动往往打开一个能隙的马约拉纳光谱附近的无隙-有隙相界。我们的研究结果表明,分馏是实验观察到的比热,自旋相关,和输运性质。

英文摘要:

Finite-temperature ($T$) properties of a Kitaev model defined on a honeycomb lattice are investigated by a quantum Monte Carlo simulation, from the viewpoint of fractionalization of quantum $S=1/2$ spins into two types of Majorana fermions, itinerant and localized. In this system, the entropy is released successively at two well-separated $T$ scales, as a clear indication of the thermal fractionalization. We show that the high-$T$ crossover, which is driven by itinerant Majorana fermions, is closely related with the development of nearest-neighbor spin correlations. On the other hand, the low-$T$ crossover originates in thermal fluctuations of fluxes composed of localized Majorana fermions, by which the spectrum of itinerant Majorana fermions is significantly disturbed. As a consequence, in the intermediate-$T$ range between the two crossovers, the system exhibits $T$-linear behavior in the specific heat and coherent transport of Majorana fermions, which are unexpected for the Dirac semimetallic spectrum in the low-$T$ limit. We also show that the flux fluctuations tend to open an energy gap in the Majorana spectrum near the gapless-gapped phase boundary. Our results indicate that the fractionalization is experimentally observable in the specific heat, spin correlations, and transport properties.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑