Enhanced Superconducting Pairing Strength near a Pure Nematic Quantum Critical Point
Enhanced Superconducting Pairing Strength near a Pure Nematic Quantum Critical Point
复制标题
DOI：
10.1103/physrevx.13.011032
复制
发表时间：
2022-02
影响因子：
12.5
通讯作者：
K. Mukasa;K. Ishida;S. Imajo;M. Qiu;M. Saito;K. Matsuura;Y. Sugimura;S. Liu;Y. Uezono;T. Otsuka;M. Čulo;S. Kasahara;Y. Matsuda;N. Hussey;T. Watanabe;K. Kindo;T. Shibauchi
中科院分区：
文献类型：
--
作者：
K. Mukasa;K. Ishida;S. Imajo;M. Qiu;M. Saito;K. Matsuura;Y. Sugimura;S. Liu;Y. Uezono;T. Otsuka;M. Čulo;S. Kasahara;Y. Matsuda;N. Hussey;T. Watanabe;K. Kindo;T. Shibauchi
在环境压力下对高温超导性的探索是物理学中的一个中心问题。在这方面，非常规超导性和量子临界点（QCP）与抑制某种形式的破序到零温度之间的关系受到了特别的关注。关键问题是QCP附近的电子对强度如何变化，这可以通过高场实验来验证。然而，这样的研究主要局限于超导体与磁性QCP，和非常规机制的可能性，其中磁QCP促进强配对仍然是一个重要的问题。在这里，我们报道了系统测量的上临界场$H_{{\rmc 2}}$在xFeSe $_{1-x}$Te$_{x}$超导体，这表现出一个QCP的电子向列性特征的自发旋转对称性破缺。随着磁场的增加，FeSe${1-x}$Te${x}$的超导相收缩成一个围绕着超导QCP的较窄的圆顶。对H_{{\rmc 2}}$的分析表明，Pauli极限场向QCP方向增强，这意味着通过QCP产生的涨落，对相互作用显著增强.值得注意的是，这种双量子态的QCP并不伴随着发散的有效质量，这与磁介导的配对不同。我们的观察为高温超导开辟了一条新的途径。
The quest for high-temperature superconductivity at ambient pressure is a central issue in physics. In this regard, the relationship between unconventional superconductivity and the quantum critical point (QCP) associated with the suppression of some form of symmetry-breaking order to zero temperature has received particular attention. The key question is how the strength of the electron pairs changes near the QCP, and this can be verified by high-field experiments. However, such studies are limited mainly to superconductors with magnetic QCPs, and the possibility of unconventional mechanisms by which nonmagnetic QCP promotes strong pairing remains a nontrivial issue. Here, we report systematic measurements of the upper critical field $H_{{\rm c2}}$ in nonmagnetic FeSe$_{1-x}$Te$_{x}$ superconductors, which exhibit a QCP of electronic nematicity characterized by spontaneous rotational-symmetry breaking. As the magnetic field increases, the superconducting phase of FeSe$_{1-x}$Te$_{x}$ shrinks to a narrower dome surrounding the nematic QCP. The analysis of $H_{{\rm c2}}$ reveals that the Pauli-limiting field is enhanced toward the QCP, implying that the pairing interaction is significantly strengthened via nematic fluctuations emanated from the QCP. Remarkably, this nonmagnetic nematic QCP is not accompanied by a divergent effective mass, distinct from the magnetically mediated pairing. Our observation opens up a nonmagnetic route to high-temperature superconductivity.