Evidence for superconductivity above 260 K in lanthanum superhydride at megabar pressures

TL;DR

This study reports evidence of superconductivity above 260 K in lanthanum superhydride at megabar pressures, achieved through a novel synthesis method and confirmed by electrical transport measurements and structural analysis.

Contribution

The paper introduces a new pulsed laser heating technique for synthesizing lanthanum superhydride at high pressures and provides experimental evidence of superconductivity near room temperature.

Findings

Resistivity drops observed around 260-280 K at 190 GPa

No structural changes detected during cooling in x-ray diffraction

Control experiments show no resistance drop in pure La

Abstract

Recent predictions and experimental observations of high Tc superconductivity in hydrogen-rich materials at very high pressures are driving the search for superconductivity in the vicinity of room temperature. We have developed a novel preparation technique that is optimally suited for megabar pressure syntheses of superhydrides using pulsed laser heating while maintaining the integrity of sample-probe contacts for electrical transport measurements to 200 GPa. We detail the synthesis and characterization, including four-probe electrical transport measurements, of lanthanum superhydride samples that display a significant drop in resistivity on cooling beginning around 260 K and pressures of 190 GPa. Additional measurements on two additional samples synthesized the same way show resistance drops beginning as high as 280 K at these pressures. The loss of resistance at these high temperatures is not observed in control experiments on pure La as well as in partially transformed samples at these pressures, and x-ray diffraction as a function of temperature on the superhydride reveal no structural changes on cooling. We infer that the resistance drop is a signature of the predicted room-temperature superconductivity in LaH10, in good agreement with density functional structure search and BCS theory calculations.