The joint research team consisting of Institute of Solid State Physics, Hefei Institute of Material Science, Chinese Academy of Sciences and the High Magnetic Field Science Center made progress in the study of the ultrahigh pressure transition metal 2H-MoS2.The research team used a diamond- , The superconductivity of 2Ha-MoS2 was first observed by low-temperature electric transport and synchrotron radiation x-ray diffraction, and the microscopic mechanism of superconductivity was explained by density functional theory calculations. The correlation results were expressed as "2Ha-MoS2 super Superconductivity under high pressure "title, published in the" Physical Review Letters ", and was selected as the editor recommended articles.
The transition metal dichalcogenide MX2 (M is a transition metal of Ti, Nb, Ta, Mo, W; X is a chalcogenide element of S, Se, Te) has a layered structure similar to graphite in terms of the XMX sandwich monolayer And the number of MX6 coordination polyhedron can be divided into 1T, 1T ', Td, 2H and other polymorphs, the electronic ground state covers charge density wave, Mott insulator, exciton insulator, semiconductors, semimetals, metals and super Lead, etc. Among them, the behavior of charge density wave and superconducting coexistence of metal 2H-NbS2, 2H-NbSe2, 2H-TaS2 and 2H-TaSe2 under atmospheric pressure is normal.Experimental studies have shown that the chemical intercalation and the application of external pressure In addition, experimental studies have shown that in the non-charge density wave of the outer ear semimetal Td-WTe2 by applying an external pressure is also applied Can induce superconductivity semiconductor 2Hc-MoS2 under normal pressure was not found charge density wave transition experimentally confirmed by chemical intercalation and the application of electrostatic bias can induce superconductivity, but so far there is no pressure-induced superconductivity Experimental evidence.
The research team based on self-built high-voltage integrated test platform, through the standard four-lead low temperature electrical transport measurements found: 2Ha-MoS2 90GPa above the superconductivity began to show superconducting transition critical temperature Tc is about 3K. As the pressure further increased Tc increased sharply and reached about 11K at about 120GPa and then maintained at about 12K within the pressure range of 130 ~ 220GPa. The measurement of high-pressure synchrotron radiation x-ray diffraction showed that 2Ha-MoS2 was within the range of 40 ~ 155GPa Structural phase transition, amorphization or decomposition, which indicates that superconductivity is the eigenstate of 2Ha-MoS2 phase. It is found by density functional calculations that superconductivity can be attributed to the high voltage-induced new hole type in 2Ha-MoS2 electronic structure The emergence of Fermi pocket.The first time in this work, the superconductivity was observed by pressure-control study in 2H transitional metal disulfide semiconductors of atmospheric pressure without charge density wave, which enriched the pressure of the transition metal dichalcogenide system - Temperature phase diagram.
Research has been funded by the state's key research and development programs, the National Natural Science Foundation of China and the Anhui Provincial Natural Science Foundation.
Figure 1. Sample and electrode layout in diamond anvil.
Figure 2.2H-MoS2 pressure-temperature phase diagram.
