Superconductivity and Structural Changes in Tantalum Disulfide under Ultrahigh Pressure
일 시 : 2021년 09월 14일 화요일 16:00
연 사 : Qing Dong 박사 (State Key Laboratory of Superhard Materials, Jilin University)
장 소 : 온라인 진행 (https://us02web.zoom.us/j/87970108931)
HOST : 김 재 용 교수님
초 록
As a major branch of two-dimensional layered materials, transition metal dichalcogenides (TMDs) have been a research hotspot due to their simple crystal structure and exotic electronic properties. Pressure, as a powerful method which can effectively tune the interlayer distance and intralayer interaction without introducing impurity, has been widely utilized in TMDs. The application of pressure on TMDs can tune insulator-metal transition, suppress charge density waves, induce superconductivity. Overall, TMDs show abundant and intriguing physical properties under high pressure. The most attractive feature of TMDs is their graphene-like layered structure. However, owing to that the applied pressure in previous researches is not very high, the changes of interlayer interaction in compressed TMDs have not been studied in depth. In addition, the influence of structural modulation on electronic properties is rarely involved in previous high-pressure researches. Based on above questions, 1T, 2H and Restacked TaS2, which are structurally stable and have exotic electronic properties at atmospheric pressure, were selected as the research objects respectively, and the changes of electronic properties and crystal structure under ultra-high pressure were investigated. In 1T-TaS2, we found a pressure-induced re-enhanced superconductivity accompanied with a structural phase transition to nonlayered structure above 45 GPa. While in 2H-TaS2, an unexpected superconducting state (SC-II) was found emerged, and its Tc enhances rapidly and reaches the maximum of 16.4 K at 157.4 GPa, which sets a new record for TMDs. As for Restacked-TaS2, we found abundant electronic property changes through whole temperature range under pressure, which are closely related to the interlayer re-arrangement and pressure-induced layer sliding. Our results show that these three TaS2 present different electrical properties and structural evolutions under high pressure, which have great importance to explore the high-pressure behavior of other TMDs.