Unconventional Superconductivity in Luttinger Semimetals: Theory of Complex Tensor Order and the Emergence of the Uniaxial Nematic State.
Unconventional Superconductivity in Luttinger Semimetals: Theory of Complex Tensor Order and the Emergence of the Uniaxial Nematic State.
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DOI：
10.1103/physrevlett.120.057002
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发表时间：
2017-07
影响因子：
8.6
通讯作者：
I. Boettcher;I. Herbut
中科院分区：
文献类型：
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作者：
I. Boettcher;I. Herbut
我们研究了在带色散中化学势接近二次带接触点的三维电子系统中的非常规超导性。短程相互作用可导致d波超导性，由复张量序参数描述。我们阐明了相应的金兹堡-朗道自由能的一般结构，并将这些概念应用于各向同性带接触点的情况。当化学势消失时，系统的基态由超导体模拟的单轴向列态给出，其特征是准粒子激发谱中的线节点。然而，与液晶中的实张量阶理论相反，这里的基态是由自由能中的六项选择的。在有限的化学势下，向列态在弱耦合和低温下具有额外的不稳定性。特别是，自由能的单环系数表明，在弱耦合下，打破时间反转对称性的真正复杂阶在能量上是有利的。我们将我们的分析与最近对半赫斯勒化合物YPtBi的测量联系起来，并讨论了立方晶体对称性的作用。
We investigate unconventional superconductivity in three-dimensional electronic systems with the chemical potential close to a quadratic band touching point in the band dispersion. Short-range interactions can lead to d-wave superconductivity, described by a complex tensor order parameter. We elucidate the general structure of the corresponding Ginzburg-Landau free energy and apply these concepts to the case of an isotropic band touching point. For a vanishing chemical potential, the ground state of the system is given by the superconductor analogue of the uniaxial nematic state, which features line nodes in the excitation spectrum of quasiparticles. In contrast to the theory of real tensor order in liquid crystals, however, the ground state is selected here by the sextic terms in the free energy. At a finite chemical potential, the nematic state has an additional instability at weak coupling and low temperatures. In particular, the one-loop coefficients in the free energy indicate that at weak coupling genuinely complex orders, which break time-reversal symmetry, are energetically favored. We relate our analysis to recent measurements in the half-Heusler compound YPtBi and discuss the role of cubic crystal symmetry.