Pressure-Induced Metallization and Structural Phase Transition in the Quasi-One-Dimensional TlFeSe2**Supported by the National Key R&D Program of China (2018YFA0305700), the National Natural Science Foundation of China (11904391, 11834016, 11874400, 11888101, 11921004), the Beijing Natural Science Foundation (Z190008), the Strategic Priority Research Program and the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (XDB25000000, QYZDBSSW- SLH013), and

Abstract

We report a comprehensive high-pressure study on the monoclinic TlFeSe2 single crystal, which is an antiferromagnetic insulator with quasi-one-dimensional crystal structure at ambient pressure. It is found that TlFeSe2 undergoes a pressure-induced structural transformation from the monoclinic phase to an orthorhombic structure above Pc ≈ 13 GPa, accompanied with a large volume collapse of ΔV/V0 = 8.3%. In the low-pressure monoclinic phase, the insulating state is easily metallized at pressures above 2 GPa; while possible superconductivity with K is found to emerge above 30 GPa in the high-pressure phase. Such a great tunability of TlFeSe2 under pressure indicates that the ternary AFeSe2 system (A = Tl, K, Cs, Rb) should be taken as an important platform for explorations of interesting phenomena such as insulator-metal transition, dimensionality crossover, and superconductivity.