arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1707.03027cond-mat.str-elcond-mat.stat-mechhep-th
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具有竞争级的狄拉克费米子:具有涌现对称性的非朗道跃迁

Dirac Fermions with Competing Orders: Non-Landau Transition with Emergent Symmetry

Toshihiro Sato, Martin Hohenadler, Fakher F. Assaad

摘要:

我们考虑一个$2+1$维狄拉克费米子模型,它具有动态生成的反对易SO(3)Néel和Z $_2$ Kekulé质量项,允许无符号量子蒙特卡罗模拟.相图是从有限尺寸标度得到的,包括Néel相和Kekulé相之间的直接和连续的过渡。费米子在跃迁过程中仍然是带隙的,我们的数据支持一个突现的SO(4)对称性统一了两个序参量。虽然我们模型的裸对称性不允许在凯库勒质量中存在携带自旋的Z $_3$涡旋,但涌现的SO(4)不变性允许用去限制的量子临界性来解释跃迁。相图还具有Néel、Kekulé和半金属相相遇的三临界点。目前,无符号的方法可以推广到各种其他质量条款,从而提供了一个新的框架来研究奇异的临界现象。

英文摘要:

We consider a model of Dirac fermions in $2+1$ dimensions with dynamically generated, anticommuting SO(3) Néel and Z$_2$ Kekulé mass terms that permits sign-free quantum Monte Carlo simulations. The phase diagram is obtained from finite-size scaling and includes a direct and continuous transition between the Néel and Kekulé phases. The fermions remain gapped across the transition, and our data support an emergent SO(4) symmetry unifying the two order parameters. While the bare symmetries of our model do not allow for spinon-carrying Z$_3$ vortices in the Kekulé mass, the emergent SO(4) invariance permits an interpretation of the transition in terms of deconfined quantum criticality. The phase diagram also features a tricritical point at which Néel, Kekulé, and semimetallic phases meet. The present, sign-free approach can be generalized to a variety of other mass terms and thereby provides a new framework to study exotic critical phenomena.

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