Venderley Jordan, Kim Eun-Ah
Cornell University, Ithaca, NY 14850, USA.
Sci Adv. 2019 Mar 29;5(3):eaat4698. doi: 10.1126/sciadv.aat4698. eCollection 2019 Mar.
Cooper pairs with a finite center-of-mass momentum form a remarkable state in which the superconducting order parameter is modulated periodically in space. Although intense interest in such a "pair-density wave" (PDW) state has emerged due to recent discoveries in high superconductors, there is little theoretical understanding of the mechanism driving this exotic state. The challenge is that many competing states lie close in energy in seemingly simple models, such as the Hubbard model, in the strongly correlated regime. Here, we show that inversion symmetry breaking and the resulting spin-valley locking can promote PDWs over more commonly found spin stripes through frustration against magnetic order. Specifically, we find the first robust evidence for a PDW within density matrix renormalization group simulation of a simple fermionic model. Our results point to a tantalizing possibility in hole-doped group VI transition metal dichalcogenides, with spin-valley locked band structure and moderate correlations.
具有有限质心动量的库珀对形成了一种非凡的状态，其中超导序参量在空间中呈周期性调制。尽管由于近期在高温超导体中的发现，人们对这种“对密度波”（PDW）状态产生了浓厚兴趣，但对于驱动这种奇异状态的机制，理论上却知之甚少。挑战在于，在强关联区域中，许多竞争状态在看似简单的模型（如哈伯德模型）中能量相近。在此，我们表明，通过对磁序的阻碍，宇称时间反演对称性破缺以及由此产生的自旋 - 能谷锁定能够促进PDW的形成，而非更常见的自旋条纹。具体而言，我们在一个简单费米子模型的密度矩阵重整化群模拟中发现了PDW的首个有力证据。我们的结果指出了在具有自旋 - 能谷锁定能带结构和适度关联的空穴掺杂VI族过渡金属二硫属化物中存在一种诱人的可能性。
