# From LaH10 to room-temperature superconductors

## TL;DR

This paper investigates the thermodynamic properties of LaH10 superconductor, compares them with BCS theory, and predicts that LaXH--type compounds could achieve higher critical temperatures than LaH10.

## Contribution

The study calculates thermodynamic parameters of LaH10 and predicts significantly higher critical temperatures for LaXH--type superconductors with X=Sc,Y.

## Key findings

- LaH10 has a critical temperature of 215-260 K at high pressures.
- Thermodynamic parameters differ from BCS theory predictions.
- LaXH--type compounds could reach critical temperatures above 220 K.

## Abstract

Thermodynamic parameters of the $\rm LaH_{10}$ superconductor were an object of our interest. $\rm LaH_{10}$ is characterised by the highest experimentally observed value of the critical temperature: $T^{a}_{C}=215$~K ($p_{a}=150$~GPa) and $T^{b}_{C}=260$~K ($p_{b}=190$~GPa). It belongs to the group of superconductors with a~strong electron--phonon coupling ($\lambda_{a}\sim 2.2$ and $\lambda_{b}\sim 2.8$). We calculated thermodynamical parameters of this superconductor and found that the values of the order parameter, the thermodynamic critical field, and the specific heat differ significantly from the values predicted by the conventional BCS theory. Due to the specific structure of the Eliashberg function for the hydrogenated compounds, the qualitative analysis suggests that the superconductors of the ${\rm La_{\delta}X_{1-\delta}H_{10}}$--type (LaXH--type) structure, where ${\rm X}\in\{{\rm Sc},{\rm Y}\}$, would exhibit significantly higher critical temperature than $T_{C}$ obtained for $\rm LaH_{10}$. In the case of LaScH we came to the following assessments: $T^{a}_{C}\in\left<220,267\right>$~K and $T^{b}_{C}\in\left<263,294\right>$~K, while the results for LaYH were: $T^{a}_{C}\in\left<218,247\right>$~K and $T^{b}_{C}\in\left<261,274\right>$~K.