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When superconductivity crosses over: From BCS to BEC
Reviews of Modern Physics ( IF 45.9 ) Pub Date : 2024-05-23 , DOI: 10.1103/revmodphys.96.025002 Qijin Chen 1 , Zhiqiang Wang 2 , Rufus Boyack 3 , Shuolong Yang 4 , K. Levin 5
Reviews of Modern Physics ( IF 45.9 ) Pub Date : 2024-05-23 , DOI: 10.1103/revmodphys.96.025002 Qijin Chen 1 , Zhiqiang Wang 2 , Rufus Boyack 3 , Shuolong Yang 4 , K. Levin 5
Affiliation
New developments in superconductivity, particularly through unexpected and often surprising forms of superconducting materials, continue to excite the community and stimulate theory. It is now becoming clear that there are two distinct platforms for superconductivity: natural and synthetic materials. The study of these artificial materials has greatly expanded in the past decade or so, with the discoveries of new forms of superfluidity in artificial heterostructures and the exploitation of proximitization. Natural superconductors continue to surprise through Fe-based pnictides and chalcogenides, and nickelates as well as others. This review presents a two-pronged investigation into such superconductors, with an emphasis on those that have come to be understood to belong somewhere between the Bardeen-Cooper-Schrieffer (BCS) and Bose-Einstein condensation (BEC) regimes. The nature of this “crossover” superconductivity, which is to be distinguished from crossover superfluidity in atomic Fermi gases, is a focus here. Multiple ways of promoting a system out of the BCS and into the BCS-BEC crossover regime are addressed in the context of concrete experimental realizations. These involve natural materials, such as organic conductors, as well as artificial, mostly two-dimensional materials, such as magic-angle twisted bilayer and trilayer graphene, or gate-controlled devices, as well as one-layer and interfacial superconducting films. Such developments should be viewed as a celebration of BCS theory, as it is now clear that, even though this theory was initially implemented with the special case of weak correlations in mind, it can be extended in a natural way to treat the case of these more exotic strongly correlated superconductors.
中文翻译:
当超导叉时:从 BCS 到 BEC
超导性的新发展,特别是通过意想不到且经常令人惊讶的超导材料形式,继续激发社区的热情并激发理论。现在越来越清楚的是,超导性有两个不同的平台:天然材料和合成材料。在过去十年左右的时间里,随着人工异质结构中新形式的超流体的发现和模仿的开发,对这些人造材料的研究得到了极大的扩展。天然超导体继续通过铁基 pnictides 和 chalcogenides 以及镍酸盐等带来惊喜。这篇综述对此类超导体进行了双管齐下的研究,重点介绍了那些被理解为属于 Bardeen-Cooper-Schrieffer (BCS) 和 Bose-Einstein 凝聚态 (BEC) 之间的超导体。这种“交叉”超导性的性质,要与原子费米气体中的交叉超流体区分开来,是这里的一个重点。在具体实验实现的背景下,讨论了将系统从 BCS 推广到 BCS-BEC 交叉制度的多种方法。这些涉及天然材料,例如有机导体,以及人造的,主要是二维材料,例如魔术角扭曲双层和三层石墨烯,或栅极控制器件,以及单层和界面超导薄膜。这样的发展应该被视为对 BCS 理论的庆祝,因为现在很明显,即使该理论最初是在考虑弱相关性的特殊情况下实施的,但它可以以自然的方式扩展以处理这些更奇特的强相关超导体的情况。
更新日期:2024-05-23
中文翻译:
当超导叉时:从 BCS 到 BEC
超导性的新发展,特别是通过意想不到且经常令人惊讶的超导材料形式,继续激发社区的热情并激发理论。现在越来越清楚的是,超导性有两个不同的平台:天然材料和合成材料。在过去十年左右的时间里,随着人工异质结构中新形式的超流体的发现和模仿的开发,对这些人造材料的研究得到了极大的扩展。天然超导体继续通过铁基 pnictides 和 chalcogenides 以及镍酸盐等带来惊喜。这篇综述对此类超导体进行了双管齐下的研究,重点介绍了那些被理解为属于 Bardeen-Cooper-Schrieffer (BCS) 和 Bose-Einstein 凝聚态 (BEC) 之间的超导体。这种“交叉”超导性的性质,要与原子费米气体中的交叉超流体区分开来,是这里的一个重点。在具体实验实现的背景下,讨论了将系统从 BCS 推广到 BCS-BEC 交叉制度的多种方法。这些涉及天然材料,例如有机导体,以及人造的,主要是二维材料,例如魔术角扭曲双层和三层石墨烯,或栅极控制器件,以及单层和界面超导薄膜。这样的发展应该被视为对 BCS 理论的庆祝,因为现在很明显,即使该理论最初是在考虑弱相关性的特殊情况下实施的,但它可以以自然的方式扩展以处理这些更奇特的强相关超导体的情况。