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倾斜多外尔半金属中的反常霍尔输运

Anomalous Hall transport in tilted multi-Weyl semimetals.

作者信息

Menon Anirudha, Basu Banasri

机构信息

Department of Physics, University of California, Davis, California 95616, United States of America.

Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata 700108, India.

出版信息

J Phys Condens Matter. 2020 Oct 28;33(4). doi: 10.1088/1361-648X/abb9b8.

Abstract

We study the effect of a perpendicular magnetic fieldon a multinode Weyl semimetal (mWSM) of arbitrary integer monopole charge, with the two Weyl multinodes separated in-space. Besides type-I mWSMs, there exist type-II mWSMs which are characterized by the tilted minimal dispersion for low-energy excitations; the Weyl points in type-II mWSMs are still protected crossings but appear at the contact of the electron and hole pockets, after the Lifshitz transition. We find that the presence of a perpendicular magnetic field quantizes the occupation pockets due to the presence of Fermi tubes. In this theory, the Hilbert space is spanned by a set ofchiral degenerate ground states, and a countably infinite number of particle-hole symmetric Landau levels (LLs). We calculate the Hall conductivity for the tilt-symmetric case of type-I mWSM using the Kubo formula, in the zero-frequency (DC) limit, and recover the well-known vacuum contribution. We compute the Fermi surface corrections and show that the expression generalizes from the formula for elementary (= 1) type-I WSMs. We derive an expression for the type-II mWSM Hall conductivity, which is bounded by a LL cutoff introduced on physical grounds. Interestingly, we find that the anomalous vacuum Hall conductivity is vanishing in the type-II phase at all temperatures. The corresponding thermal Hall and Nernst conductivities are evaluated and characterized for both phases. The qualitative and quantitative observations presented here may serve in the characterization of generic mWSMs of both types.

摘要

我们研究了垂直磁场对具有任意整数单极电荷的多节点外尔半金属(mWSM)的影响,该多节点外尔半金属中的两个外尔节点在空间上是分开的。除了I型mWSM之外,还存在II型mWSM,其特征是低能激发具有倾斜的最小色散;II型mWSM中的外尔点仍然是受保护的交叉点,但在里夫希茨转变之后出现在电子和空穴口袋的接触处。我们发现,由于费米管的存在,垂直磁场的存在使占据口袋量子化。在此理论中,希尔伯特空间由一组手征简并基态以及可数无穷多个粒子 - 空穴对称的朗道能级(LLs)构成。我们使用久保公式在零频率(直流)极限下计算了I型mWSM倾斜对称情况下的霍尔电导率,并恢复了著名的真空贡献。我们计算了费米面修正,并表明该表达式是从基本(= 1)型I型WSM的公式推广而来的。我们推导了II型mWSM霍尔电导率的表达式,该表达式由基于物理原因引入的LL截止界定。有趣的是,我们发现在所有温度下,II型相中反常真空霍尔电导率都为零。对两个相的相应热霍尔电导率和能斯特电导率进行了评估和表征。这里给出的定性和定量观察结果可能有助于对这两种类型的一般mWSM进行表征。

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