Classification of gapless Z2 spin liquids in three-dimensional Kitaev models
Classification of gapless Z2 spin liquids in three-dimensional Kitaev models
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DOI：
10.1103/physrevb.93.085101
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发表时间：
2016-02-01
影响因子：
3.7
通讯作者：
Trebst, Simon
中科院分区：
文献类型：
--
作者：
O'Brien, Kevin;Hermanns, Maria;Trebst, Simon
受挫的量子磁体可能含有非传统的自旋-液体基态，在这种基态中，基本磁矩会细分为新出现的自由度。虽然量子数的小数化是现代凝聚态物理学中反复出现的主题之一，但设计一个跟踪这一现象的受控分析框架往往仍然是一个挑战。一个值得注意的例外是精确可解的Kitaev模型，在该模型中，自旋自由度细分为Majorana费米子和Z(2)规范场。在这里，我们讨论了三维Kitaev模型中的分馏化物理，并证明了巡回的Majorana费米子一般形成(半)金属，取决于潜在的晶格结构，表现出Majorana费米面、节线或拓扑保护的Weyl节点。我们证明，这些Majorana金属的性质可以从对给定晶格的投影时间反转和反转对称性的初等对称性分析中推断出来。这使得我们能够对三维最基本的三配位晶格的Kitaev模型的无间隙自旋液体进行全面的分类。我们通过解决时间反转、对称性破缺和额外相互作用的影响进一步扩展了这一分类。
Frustrated quantum magnets can harbor unconventional spin-liquid ground states in which the elementary magnetic moments fractionalize into new emergent degrees of freedom. While the fractionalization of quantum numbers is one of the recurring themes in modern condensed matter physics, it often remains a challenge to devise a controlled analytical framework tracking this phenomenon. A notable exception is the exactly solvable Kitaev model, in which spin degrees of freedom fractionalize into Majorana fermions and a Z(2) gauge field. Here, we discuss the physics of fractionalization in three-dimensional Kitaev models and demonstrate that the itinerant Majorana fermions generically form a (semi) metal which, depending on the underlying lattice structure, exhibits Majorana Fermi surfaces, nodal lines, or topologically protected Weyl nodes. We show that the nature of these Majorana metals can be deduced from an elementary symmetry analysis of the projective time-reversal and inversion symmetries for a given lattice. This allows us to comprehensively classify the gapless spin liquids of Kitaev models for the most elementary tricoordinated lattices in three dimensions. We further expand this classification by addressing the effects of time-reversal symmetry breaking and additional interactions.