High-temperature superconductivity in hydrides: experimental evidence and details

TL;DR

This paper reviews experimental evidence confirming high-temperature superconductivity in hydrides under high pressures, addressing criticisms and supporting the conventional phonon-mediated BCS theory.

Contribution

It provides detailed experimental data that refutes alternative theories and clarifies the nature of superconductivity in hydrides at high pressures.

Findings

Superconductivity observed at temperatures up to 200 K in hydrides.

Experimental results align with BCS theory predictions.

Criticisms against superconductivity claims are addressed and refuted.

Abstract

Since the discovery of superconductivity at 200 K in H3S [1] similar or higher transition temperatures, Tcs, have been reported for various hydrogen-rich compounds under ultra-high pressures [2]. Superconductivity was experimentally proved by different methods, including electrical resistance, magnetic susceptibility, optical infrared, and nuclear resonant scattering measurements. The crystal structures of superconducting phases were determined by X-ray diffraction. Numerous electrical transport measurements demonstrate the typical behaviour of a conventional phonon-mediated superconductor: zero resistance below Tc, the shift of Tc to lower temperatures under external magnetic fields, and pronounced isotope effect. Remarkably, the results are in good agreement with the theoretical predictions, which describe superconductivity in hydrides within the framework of the conventional BCS theory. However, despite this acknowledgment, experimental evidence for the superconducting state in these compounds has recently been treated with criticism [3, 4], which apparently stems from misunderstanding and misinterpretation of complicated experiments performed under very high pressures. Here, we describe in greater detail the experiments revealing high-temperature superconductivity in hydrides under high pressures. We show that the arguments against superconductivity [3, 4] can be either refuted or explained. The experiments on the high-temperature superconductivity in hydrides clearly contradict the theory of hole superconductivity [4] and eliminate it [3].