Pressure-induced high-temperature superconductivity retained without pressure in FeSe single crystals

Abstract

To raise the superconducting-transition temperature (Tc) has been the driving force for the long-sustained effort in superconductivity research. Recent progress in hydrides with Tcs up to 287 K under pressure of 267 GPa has heralded a new era of room temperature superconductivity (RTS) with immense technological promise. Indeed, RTS will lift the temperature barrier for the ubiquitous application of superconductivity. Unfortunately, formidable pressure is required to attain such high Tcs. The most effective relief to this impasse is to remove the pressure needed while retaining the pressure-induced Tc without pressure. Here, we show such a possibility in the pure and doped high-temperature superconductor (HTS) FeSe by retaining, at ambient pressure via pressure quenching (PQ), its Tc up to 37 K (quadrupling that of a pristine FeSe at ambient) and other pressure-induced phases. We have also observed that some phases remain stable without pressure at up to 300 K and for at least 7 d. The observations are in qualitative agreement with our ab initio simulations using the solid-state nudged elastic band (SSNEB) method. We strongly believe that the PQ technique developed here can be adapted to the RTS hydrides and other materials of value with minimal effort.

Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH22

“…In principle, this suggests that polyhydrides can maintain their structure during decompression, as has been recently shown for FeSe. [ 32 ]…”

Fragile Pressure-Induced Magnetism in FeSe Superconductors with a Thickness Reduction

“…30,31 Concomitantly, the superconductivity is enhanced in a three-step process and reaches ∼40 K at around 60 kbar. Very recently, this high-T c superconducting phase has been shown to be metastable when the pressure is rapidly removed at 4.2 K. 59 The novel phases in FeSe can also be tuned by combining chemical substitution and pressure. 32,46−53 In FeSe 1−x S x , the nematic phase is suppressed as sulfur content increases, and a nematic quantum critical point is observed without the presence of magnetism.…”

“…Recent studies suggest that near the quantum critical points of nematicity and SDW order, both enhanced nematic fluctuations and magnetic fluctuations can mediate Cooper pairing. ,− However, due to the proximity of the nematic phase and the magnetically ordered phase the interplay among superconductivity, nematicity, and magnetism remains elusive. FeSe, as another prominent member of IBS, has drawn intensive attention. ,,,− Bulk FeSe undergoes a nematic phase transition at T s ∼ 90 K and further becomes superconducting at T c = 9 K, without the presence of magnetism. ,− Under pressure, the SDW phase can be induced at around 10 kbar, ,, which develops into a dome shape in the temperature–pressure ( T – p ) phase diagram and spans more than 40 kbar. , Concomitantly, the superconductivity is enhanced in a three-step process and reaches ∼40 K at around 60 kbar. Very recently, this high- T c superconducting phase has been shown to be metastable when the pressure is rapidly removed at 4.2 K .…”

The drastic effect of the impurity scattering on the electronic and superconducting properties of Cu-doped FeSe

“…Additionally, the Cu-substitution in FeSe leads to a metal-to-insulator transition for small substitutions (x = 0.04) [14,15,17] and it can induce local magnetism around the Cu sites for higher substitutions [14]. Under high pressure, the insulating behaviour is suppressed and the superconductivity is restored as the magnetic fraction [18][19][20]. Thus, the Cu substitution in FeSe can reveal important information about the nature of the superconducting and normal states, and whether an insulating state can be tuned into a high-T c superconductor under applied pressure in an iron-based superconductor.…”