二维晶体中的高温超导与量子格里菲斯奇异性

High-temperature superconductivity and quantum Griffith singularity in two-dimensional crystal

超导体因其零电阻与完全抗磁性等性质,已成为凝聚态物理与材料科学领域最重要的研究方向之一.近年来,随着单晶薄膜制备工艺的提高,二维晶体超导体逐渐发展为新的前沿热点,其中出现的一些新奇物理现象,如高温超导和量子相变等,得到了学术界的广泛关注.简要介绍了二维晶体超导体的研究背景和基本特性,并分两个部分重点介绍了二维晶体中高温超导和量子相变两类重要现象.第一部分总结性回顾了二维高温超导体单原胞层铁硒/钛酸锶(FeSe/STO)的发现和验证,实验中发现的基本性质并探讨了其可能的超导机理.第二部分着重介绍量子相变和量子格里菲斯奇异性,包括其理论模型、在二维晶体超导中的实验发现和相应的分析.最后总结全文,并对相关领域的发展进行了展望.

Superconductors have become one of the most important directions in condensed matter physics and materials science due to their unique properties incuding zero-resistance and perfect diamagnetism. With the development of the fabrication technique of two-dimensional（2D） single crystals, 2D superconductors have recently come to be a new research frontier, in which novel physics phenomena, such as high-temperature superconductivity and quantum phase transitions, have emerged and received wide attention. In this artcle, we first briefly review the research background and basic properties of 2D superconductors. Then, focusing on two important classes of phenomena—high-temperature superconductivity and quantum phase transitions, the article is organized into two parts. In the first part, we introduce a typical example of high-temperature superconductivity in 2D systems, the ultrathin FeSe films grown on SrTiO_3（STO）substrate, including the experimental properties and mechanism discussions. In the second part, as an example of quantum phase transitions in 2D systems, an overview of the theories and experiments of the newly-discovered quantum Griffiths singularity in 2D crystalline superconductors is given. In the end, we summary the high-temperature superconductivity and quantum Griffiths singularity in 2D crystals and provide an outlook of the future development in the relevant frontiers.