Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.
Nat Commun. 2017 Feb 17;8:14467. doi: 10.1038/ncomms14467.
Controlled access to the border of the Mott insulating state by variation of control parameters offers exotic electronic states such as anomalous and possibly high-transition-temperature (T) superconductivity. The alkali-doped fullerides show a transition from a Mott insulator to a superconductor for the first time in three-dimensional materials, but the impact of dimensionality and electron correlation on superconducting properties has remained unclear. Here we show that, near the Mott insulating phase, the upper critical field H of the fulleride superconductors reaches values as high as ∼90 T-the highest among cubic crystals. This is accompanied by a crossover from weak- to strong-coupling superconductivity and appears upon entering the metallic state with the dynamical Jahn-Teller effect as the Mott transition is approached. These results suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity with high-T and high-H.
通过控制参数来控制莫特绝缘状态的边界，可以提供奇异的电子态，例如异常和可能具有高转变温度（T）的超导性。 碱掺杂富勒烯首次在三维材料中从莫特绝缘体转变为超导体，但维度和电子相关对超导性质的影响仍不清楚。 在这里，我们表明，在莫特绝缘相附近，富勒烯超导体的上临界场 H 达到高达约 90 T 的值-在立方晶体中是最高的。 这伴随着从弱耦合到强耦合超导的转变，并且随着动态 Jahn-Teller 效应接近莫特转变而进入金属态时出现。 这些结果表明，分子电子结构和强电子相关之间的协同相互作用在实现具有高 T 和高 H 的稳健超导性方面起着关键作用。
