Recently, the joint research team of Institute of Solid State Physics, Hefei Institute of Material Science and High Magnetic Field Science Center, Chinese Academy of Sciences, for the first time in a new material under high pressure - molybdenum disulfide (2H structure transition metal dichalcogenide: 2H- MoS2) observed in the superconducting phenomenon.Relevant research was selected as editor of the recommended article, published in "Physical Review Letters."
Superconductivity is a macroscopic quantum phenomenon characterized by the complete disappearance of the electrical resistance of a material, which usually occurs at very low temperatures. When the material is in the superconducting state, it has zero resistance, complete diamagnetic and superconducting tunneling effects And other unique properties in the power transmission, medical equipment magnets, microwave devices and magnetic levitation trains, etc. has a unique advantage since 1911 Holland Leiden University H Carmelin Arnold found mercury below 4.2K superconductivity After that, due to its extensive application prospects, people are always diligently pursuing the development of new superconducting materials and have become the mainstream in the field of material physics.
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 polymorphism of MX6 coordination polyhedron can be divided into 1T, 1T ', Td, 2H and other polymorphs.Experimental studies have shown that through the chemical intercalation or the application of external pressure and other regulatory means, in some transition metal dichalcogen Such as exciton insulator 1T-TiSe2, Mott insulator 1T-TaS2 and the outer ear semimetal Td-WTe2, etc. For the semiconductor 2H-MoS2, although it has been experimentally confirmed that by chemical intercalation and electrostatic field Bias can induce superconductivity, but so far no experimental evidence of pressure-induced superconductivity has emerged.
To this end, researchers independently build high-pressure integrated test platform, the use of diamond on the anvil-generated high pressure conditions, low temperature electrical transport measurements found: molybdenum disulfide at 90GPa (900000 atmospheric pressure) or so under the conditions of pressure As a superconductor, the critical temperature of superconducting transition can be as high as 12K within the pressure range of 130 ~ 220GPa (near the pressure of the Earth's outer core), and the microscopic mechanism of superconductivity can be explained by density functional theory calculations.
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. Standard four-lead layout of the sample and electrode in the high pressure generating device for diamond anvil anvil under an optical microscope with a circular profile of a diamond countertop with a diameter of 100 micrometers. In the experiment, a pair of counter- Sample pressure exerting extreme pressure on the sample.
Figure 2. Pressure-temperature phase diagram of molybdenum disulfide.
