Pressure-Induced Isostructural Phase Transition and Correlation of FeAs Coordination with the Superconducting Properties of 111-Type Na_1–xFeAs

Abstract

The effect of pressure on the crystalline structure and superconducting transition temperature (T(c)) of the 111-type Na(1-x)FeAs system using in situ high-pressure synchrotron X-ray powder diffraction and diamond anvil cell techniques is studied. A pressure-induced tetragonal to tetragonal isostructural phase transition was found. The systematic evolution of the FeAs(4) tetrahedron as a function of pressure based on Rietveld refinements on the powder X-ray diffraction patterns was obtained. The nonmonotonic T(c)(P) behavior of Na(1-x)FeAs is found to correlate with the anomalies of the distance between the anion (As) and the iron layer as well as the bond angle of As-Fe-As for the two tetragonal phases. This behavior provides the key structural information in understanding the origin of the pressure dependence of T(c) for 111-type iron pnictide superconductors. A pressure-induced structural phase transition is also observed at 20 GPa.

High Pressure Induced Insulator-to-Semimetal Transition through Intersite Charge Transfer in NaMn7O12

“…which gives rise to the metallic phase. In some cases, however, isostructural MIT can take place when the crystallographic modifications induced by applied pressure modulate the structural features without symmetry breaking, as in the case of PrNiO3 [12], metal osmium [13], FeAs [14] and VO2 [15]. In WSe2, the MIT is caused by the anisotropic character of the compressibility, which induces a structural transition characterized by a sliding of the 2D layers [16].…”

Electrical resistivity of single crystals of LaFeAsO under applied pressure

“…[3][4][5][6] As a function of chemical substitution or applied pressure, the phase diagrams of these materials exhibit a rich interplay of different phenomena, including structural transitions, commensurate and incommensurate spin-density wave (SDW) ordering, and high temperature superconductivity. [5][6][7][8][9][10][11][12][13] In several iron-based materials, the appearance of superconductivity occurs following a smooth suppression of SDW order. Among the materials in which such a continuous suppression is observed are, e.g., BaFe 2 As 2 (under both chemical substitution and applied pressure) 14 and fluorine-substituted CeFeAsO 1−x F x .…”

Strain-Induced Isostructural and Magnetic Phase Transitions in Monolayer MoN2

“…However, such instances are still rare and the transition usually requires a very high pressure that is not easily accessible. [4][5][6] Starting from the discovery of graphene, 7 the field of two-dimensional (2D) materials has undergone rapid development in the past decade. Many new kinds of 2D materials have been proposed and fabricated, which exhibit a vast range of novel material properties, not seen in the usual 3D bulk materials.…”