Dynamics and superconductivity in compressed lanthanum superhydride (original) (raw)

Evidence for Superconductivity above 260 K in Lanthanum Superhydride at Megabar Pressures

Physical Review Letters, 2019

Recent predictions and experimental observations of high T c 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 modulated laser heating while maintaining the integrity of sample-probe contacts for electrical transport measurements to 200 GPa. We detail the synthesis and characterization of lanthanum superhydride samples, including fourprobe electrical transport measurements that display significant drops in resistivity on cooling up to 260 K and 180-200 GPa, and resistivity transitions at both lower and higher temperatures in other experiments. Additional current-voltage measurements, critical current estimates, and lowtemperature x-ray diffraction are also obtained. We suggest that the transitions represent signatures of superconductivity to near room temperature in phases of lanthanum superhydride, in good agreement with density functional structure search and BCS theory calculations.

Superconductivity at 253 K in lanthanum–yttrium ternary hydrides

Materials Today, 2021

Here we report the high-pressure synthesis of a series of lanthanum-yttrium ternary hydrides obtained at pressures of 170-196 GPa via the laser heating of P6 3 /mmc LaY alloys with ammonia borane. As a result, we discovered several novel compounds: cubic hexahydride (La,Y)H 6 and decahydrides (La,Y) H 10 with a maximum critical temperature T C $ 253 K and an extrapolated upper critical magnetic field B C2 (0) of up to 135 T at 183 GPa. The current-voltage measurements show that the critical current density J C in (La,Y)H 10 is 12-27.7 kA/mm 2 at 4.2 K, which is comparable with that of commercial superconducting wires such as NbTi and Nb 3 Sn. (La,Y)H 6 and (La,Y)H 10 are among the first examples of ternary high-T C superconducting hydrides. Our experiments show that part of metal atoms in the structures of recently discovered Im3m-YH 6 and Fm3m-LaH 10 can be replaced with lanthanum ($70%) and yttrium ($25%), respectively, with the formation of unique ternary superhydrides containing metal-encapsulated cages La@H 24 and Y@H 32 , which are specific for Im3m-LaH 6 and Fm3m-YH 10. This work demonstrates that hydrides, unstable in pure form such as LaH 6 and YH 10 , may nevertheless be stabilized at relatively low pressures in solid solutions with superhydrides having the desired structure.