Chemical Pressure Boost Record‐High Superconductivity in van der Waals Materials FeSe_1−xS_x

Abstract

High pressure has become a powerful platform for creating and controlling novel states of matter, including high temperature (Tc) superconductivity. However, the emergent phenomena generally disappear as high pressure is removed and cloud prospects for future applications. Here, from a distinguishing perspective, FeSe1−xSx is reported as 2D van der Waals materials with extraordinary high‐Tc at ambient pressure, where the superconductivity is boosted by extreme “chemical pressure” inside the materials. Superior to external high pressure, isovalent S substitution in FeSe leads to a much greater compression rate within the superconducting iron‐chalcogenide layer, which guarantees an unabridged superconducting dome that peaked at 37.5 K. Density functional theory calculations reveal that the decreased lattice and structural parameters contribute together for the shift of Fe 3dx2−y2 orbital, which creates a new hole‐pocket at the Fermi level that intimately correlated with the enhanced superconductivity. This study demonstrates the design of materials with optimized superconductivity by introducing chemical pressure.

Iron Selenide Nanowire Bundles for Microwave Communication Technology

“…However, as the bond length of Yb–Se (280.9 pm) is shorter than that of Yb‐Yb (358.8 pm) [ 19 ] due to the stronger coulombic interactions unreacted (broken bonds) Se atoms capture Yb atoms and forms YbSe at the ultrathin interface between Yb and FeSe 2 . Similar mechanism revealing the formation of Al 2 Se 3 at the Al/FeSe 2 interfaces is also possible due to the stronger interactions originated by the shorter bond length of Al–Se (235 [ 20 ] ) compared to Fe–Se (239 pm [ 21 ] ).…”

Calibration of local chemical pressure by optical probe

“…Internal P chem in a given compound can be generated by chemical substitution with smaller/larger ions in order to induce cell contraction/expansion (equivalent to positive/negative P chem ) [ 21 , 30–35 ]. For example, the quantum critical temperatures of Fe-based superconductors BaFe 2 As 2- x P x and FeSe 1- x S x can be dramatically increased by partial replacement of As/Se by smaller P/S, respectively, yielding equivalent performance compared to the un-doped bulk analogs under P phy [ 31 , 35 ]. The above discoveries show that P chem can simulate P phy at scaled-up yield and lower cost to a great extent.…”