Enhanced superconductivity in the vicinity of CDW quantum critical points in Pd-intercalated TaSe2
일 시 : 2021년 07월 29일 목요일 16:00
연 사 : 김 기 훈 교수 (서울대학교 물리천문학부)
장 소 : 온라인 진행 ( https://us02web.zoom.us/j/3956604859 )
HOST : 신 상 진 교수님
초 록
We present doping and pressure induced optimization of superconductivitiy, particularly focusing on tuning of electronic states in Pd-intercalated TaSe2 PdxTaSe2, in which superconducting transition is optimized from 0.14 (TaSe2) to 3.1 K (x=~0.08) with simultaneous suppression of a commensurate charge density wave (CDW) state. We found that the Pd intercalation can involve a Lifshitz transition in the underlying electronic states at normal states without CDW ground states, which seems to be useful for increasing density of states (DOS) and electron-phonon coupling and in turn two band BCS superconductivity at low temperatures, arbeit its relative importance to enhace superconductivity is not clear yet. Furthermore, an increase of DOS in the vicinity of a doping induced collapse of a commensurate CDW state can certainly help increaseing DOS and opmizing superconducting transition. Although it was not clear with intercalation, with tuning of pressure, we found that a second order quantum phase transition of a CDW transtion can occur around 22 GPa and fluctuating CDW ground states can instigate the superconductivity up to 8.3 K. With systematic Raman and transport results, we discuss how a CDW quantum crticality and related fluctuation can be involved in the process of boosting up superconductivity with pressure.