Pressure-Induced Metallization and Structural Phase Transition in the Quasi-One-Dimensional TlFeSe₂*

Abstract

We report a comprehensive high-pressure study on the monoclinic TlFeSe 2 single crystal, which is an antiferromagnetic insulator with quasi-one-dimensional crystal structure at ambient pressure. It is found that TlFeSe 2 undergoes a pressure-induced structural transformation from the monoclinic phase to an orthorhombic structure above P c ≈ 13 GPa, accompanied with a large volume collapse of Δ V / V 0 = 8.3%. In the low-pressure monoclinic phase, the insulating state is easily metallized at pressures above 2 GPa; while possible superconductivity with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>T</mml:mi> <mml:mi mathvariant="normal">c</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">onset</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>∼</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:math> K is found to emerge above 30 GPa in the high-pressure phase. Such a great tunability of TlFeSe 2 under pressure indicates that the ternary A FeSe 2 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 .