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arXiv 1906.08280cond-mat.supr-con
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低掺杂铜氧化物超导体中的初始环电流序

Incipient loop current order in the under-doped cuprate superconductors

Saheli Sarkar, Debmalya Chakraborty, Catherine Pépin

摘要:

越来越多的实验证据表明,在欠掺杂的氧化铜基(铜酸盐)超导体的赝能隙态中,离散对称性破缺如时间反演($\mathcal{T}$)、宇称($\mathcal{P}$)和C $_{4}$晶格旋转。离散的对称性破缺表明了一个真正的相变到有序状态。详细的热力学理解这些订单可以回答各种困惑的性质有关的过渡在赝能隙温度T $^*$。在本工作中,我们研究了$\mathcal{T-P}$对称性破缺的热力学特征,考虑了超导性和键密度波两个主要的阶数。BDW可以产生调制电荷和电流密度。这个框架考虑到了无处不在的电荷密度波和SC之间的复杂竞争,这是突出的各种铜酸盐在欠掺杂制度。我们表明,在平均场方法的竞争BDW和SC订单,$\mathcal{T-P}$打破共存的BDW和SC的基态可以稳定,提供BDW本身打破$\mathcal{T}-\mathcal{P}$。但是这种基态在更高的温度下就不再出现了。然而,我们发现,在SC和BDW的波动可以驱动出现一个新的不寻常的平移对称性保持秩序,由于抢先相变自发打破$\mathcal{T-P}$在较高的温度之前的主要订单集。我们把这个顺序称为磁电回路电流(MELC)顺序。我们提出了这种新的初始MELC顺序的相变的可能性质,并讨论了一些实验相关性。

英文摘要:

There are growing experimental evidence which indicate discrete symmetry breaking like time-reversal ($\mathcal{T}$), parity ($\mathcal{P}$) and C$_{4}$ lattice rotation in the pseudo-gap state of the under-doped copper-oxide based (cuprate) superconductors. The discrete symmetry breaking manifests a true phase transition to an ordered state. A detailed thermodynamic understanding of these orders can answer various puzzles related to the nature of the transition at the pseudo-gap temperature T$^*$. In this work, we investigate thermodynamic signature of $\mathcal{T-P}$ symmetry breaking considering superconductivity (SC) and bond-density wave (BDW) as two primary orders. The BDW can generate both modulating charge and current densities. This framework takes into account an intricate competition between the ubiquitous charge density wave and SC, which is prominent in various cuprates in the under-doped regime. We demonstrate that within mean-field approach of competing BDW and SC orders, a $\mathcal{T-P}$ breaking ground state of coexisting BDW and SC can be stabilized, provided the BDW itself breaks $\mathcal{T}-\mathcal{P}$. But this ground state ceases to occur at higher temperatures. However, we show that fluctuations in SC and BDW can drive emergence of a new unusual translational symmetry preserving order due to a preemptive phase transition by spontaneously breaking $\mathcal{T-P}$ at a higher temperature before the primary orders set in. We refer this order to be magneto-electric loop current (MELC) order. We present possible nature of phase transition for this new incipient MELC order and discuss some experimental relevance.

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