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Theory of competing excitonic orders in insulatingWTe2monolayers
Physical Review B ( IF 3.2 ) Pub Date : 2021-09-22 , DOI: 10.1103/physrevb.104.125133
Yves H. Kwan 1 , T. Devakul 2 , S. L. Sondhi 2 , S. A. Parameswaran 1
Affiliation  

We develop a theory of the excitonic phase recently proposed as the zero-field insulating state observed near charge neutrality in monolayer WTe2. Using a Hartree-Fock approximation, we numerically identify two distinct gapped excitonic phases: a spin density wave state for weak nonzero interaction strength and spin spiral order at stronger interactions, separated by a narrow window of a nonexcitonic quantum spin Hall insulator. We introduce a simplified model capturing key features of the WTe2 band structure, in which these phases appear as distinct valley ferromagnetic orders. We link the competition between the excitonic phases to the orbital structure of electronic wave functions at the Fermi surface and hence its proximity to the underlying gapped Dirac point in WTe2. We briefly discuss collective modes of the two excitonic states, and comment on implications for experiments.

中文翻译:

绝缘WTe2单层中竞争激子阶的理论

我们开发了最近提出的激子相理论,作为在单层中在电荷中性附近观察到的零场绝缘状态 WTe2. 使用 Hartree-Fock 近似,我们在数值上确定了两个不同的有隙激子相:弱非零相互作用强度的自旋密度波态和更强相互作用时的自旋螺旋顺序,由非激子量子自旋霍尔绝缘体的窄窗口隔开。我们引入了一个简化的模型来捕捉WTe2带结构,其中这些相以不同的谷铁磁顺序出现。我们将激子相之间的竞争与费米表面上电子波函数的轨道结构联系起来,因此它靠近下面的有隙狄拉克点WTe2. 我们简要讨论了两种激子态的集体模式,并评论了对实验的影响。
更新日期:2021-09-22
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