Recent New Developments in Superconductors

Abstract

Excitement ran high earlier this year among researchers on superconductivity, as also among the enthusiasts of a variety of applications of superconductors, due to two separate claims made on observations of superconductivity at room temperature.The first claim was by a research group from University of Rochester, USA in March 2023 on N-doped lutetium hydride (NLH), under application of mild pressures [1], and the second was by a S. Korean research group who reported superconductivity at ambient pressure and temperatures up to 127 °C (400 kelvin), on a compound of approximate composition Pb10-xCux(PO4)6O, dubbed LK-99 [2].Even though the phenomenon of superconductivity is known now for over 112 years [3], any news of ambient temperature superconductivity creates a buzz because superconducting materials discovered thus far, which include metals, alloys, chalcogenides, oxides, and even organic compounds, exhibit superconductivity only when cooled to low temperatures.Cuprate ceramics, for instance, show superconductivity at ~35 K for the system Ba-La-Cu-O, 90 K for YBa2Cu3O7-δ, and 133K for HgBa2Ca2Cu3O>8, all at ambient pressure.Some hydrides do show superconductivity at warmer temperatures, or even at room temperature, but need to be compressed under high pressures before they do so [4, 5].When Dr. Ranga Dias and his collaborators published that NLH showed superconductivity at room temperature (21 degrees Celsius, or 294 degrees Kelvin), under moderate applied pressure of just 10 kilobars (i.e., 145,000 pounds psi) [1], the lowest ever to drive superconductivity in hydrides, it was highlighted by the international press, the very next day.Why?For two reasons: first, a superconductor exhibits no resistance to the flow of electricity; and second, magnetic fields are expelled from the materials in a superconducting state, allowing magnets to levitate over them.This highlights the potential of superconducting materials for applications in at least three important sectors that impact our lives: (a) Energy, with applications in generators and motors, power transmission and distribution, energy storage systems, and magnets for fusion power and for magnetohydrodynamic power; (b) Transportation, by using superconducting magnets for levitated trains, ship propulsion, and for automobiles; and (c) Healthcare, when employed in magnetic resonance imaging (MRI), and magnetoencephalography (MEG), etc.However, many scientists greeted the results by Dr. Dias with scepticism because an earlier paper by him and his colleagues describing near room-temperature superconductivity in a different material had been retracted by Nature [6].

Abstract of "Recent New Developments in Superconductors" by Jatinder Vir Yakhmi, https://doi.org/10.61343/jcm.v1i02.16, used under its Creative Commons Attribution license (CC-BY); markup removed, otherwise unmodified.