Hoshino Shintaro, Werner Philipp
RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198 Saitama, Japan.
Department of Physics, University of Fribourg, 1700 Fribourg, Switzerland.
Phys Rev Lett. 2017 Apr 28;118(17):177002. doi: 10.1103/PhysRevLett.118.177002.
The alkali-doped fullerides A_{3}C_{60} are half-filled three-orbital Hubbard systems which exhibit an unconventional superconducting phase next to a Mott insulator. While the pairing is understood to arise from an effectively negative Hund coupling, the highly unusual Jahn-Teller metal near the Mott transition, featuring both localized and itinerant electrons, has not been understood. This property is consistently explained by a previously unrecognized phenomenon: the spontaneous transition of multiorbital systems with negative Hund coupling into an orbital-selective Mott state. This symmetry-broken state, which has no ordinary orbital moment, is characterized by an orbital-dependent two-body operator (the double occupancy) or an orbital-dependent kinetic energy and may be regarded as a diagonal-order version of odd-frequency superconductivity. We propose that the recently discovered Jahn-Teller metal phase of Rb_{x}Cs_{3-x}C_{60} is an experimental realization of this novel state of matter.
碱掺杂富勒化物A₃C₆₀是半填充的三轨道哈伯德体系，在莫特绝缘体附近呈现出非常规超导相。虽然配对被认为源于有效的负洪德耦合，但莫特转变附近高度不寻常的 Jahn - 泰勒金属，其兼具局域电子和巡游电子，尚未得到理解。这一性质可以通过一种此前未被认识到的现象得到一致解释：具有负洪德耦合的多轨道体系自发转变为轨道选择性莫特态。这种对称性破缺态没有普通的轨道磁矩，其特征是一个依赖于轨道的两体算符（双占据）或依赖于轨道的动能，并且可以被视为奇数频率超导的对角序版本。我们提出，最近发现的RbₓCs₃₋ₓC₆₀的Jahn - 泰勒金属相是这种新型物质状态的实验实现。
