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arXiv 2109.01415cond-mat.stat-mechcond-mat.str-el
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手征Ashkin-Teller模型中的公度-非公度跃迁

Commensurate-incommensurate transition in the chiral Ashkin-Teller model

Samuel Nyckees, Frédéric Mila

摘要:

利用角转移矩阵重整化群(CTMRG)算法研究了正方晶格上的经典手征Ashkin-Teller模型.我们发现,在存在手征扰动的情况下,周期-4相的熔化根据Ashkin-Teller模型中四自旋项的系数而采取不同的形式。在两个解耦的伊辛模型的时钟极限附近,当引入手征时,系统经历了两步无公度-无公度跃迁,高温时出现了Kosterlitz-Incentiless跃迁,低温时出现了Pokrovsky-Talapov跃迁.相比之下,接近四态Potts模型,我们认为存在一个独特的手性普适性类的不对称-不相称的过渡,并存在一个Lifshitz点,其中有序,无序和浮动相满足。最后,我们绘制了整个相图,结果与Huse和Fisher 40年前的预测定性一致。

英文摘要:

We investigate the classical chiral Ashkin-Teller model on a square lattice with the corner transfer matrix renormalisation group (CTMRG) algorithm. We show that the melting of the period-4 phase in the presence of a chiral perturbation takes different forms depending on the coefficient of the four-spin term in the Ashkin-Teller model. Close to the clock limit of two decoupled Ising models, the system undergoes a two-step commensurate-incommensurate transition as soon as the chirality is introduced, with an intermediate critical floating phase bounded by a Kosterlitz-Thouless transition at high temperature and a Pokrovsky-Talapov transition at low temperature. By contrast, close to the four-states Potts model, we argue for the existence of a unique commensurate-incommensurate transition that belongs to the chiral universality class, and for the presence of a Lifshitz point where the ordered, disordered and floating phases meet. Finally, we map the whole phase diagram, which turns out to be in qualitative agreement with the 40 year old prediction by Huse and Fisher.

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