Temperature and quantum anharmonic lattice effects on stability and superconductivity in lutetium trihydride

Abstract

In this work, we resolve conflicting experimental and theoretical findings related to the dynamical stability and superconducting properties of $$Fm\bar{3}m$$ F m 3 ¯ m -LuH3, which was recently suggested as the parent phase harboring room-temperature superconductivity at near-ambient pressures. Including temperature and quantum anharmonic lattice effects in our calculations, we demonstrate that the theoretically predicted structural instability of the $$Fm\bar{3}m$$ F m 3 ¯ m phase near ambient pressures is suppressed for temperatures above 200 K. We provide a p–T phase diagram for stability up to pressures of 6 GPa, where the required temperature for stability is reduced to T > 80 K. We also determine the superconducting critical temperature Tc of $$Fm\bar{3}m$$ F m 3 ¯ m -LuH3 within the Migdal-Eliashberg formalism, using temperature- and quantum-anharmonically-corrected phonon dispersions, finding that the expected Tc for electron-phonon mediated superconductivity is in the range of 50–60 K, i.e., well below the temperatures required to stabilize the lattice. When considering moderate doping based on rigidly shifting the Fermi level, Tc decreases for both hole and electron doping. Our results thus provide evidence that any observed room-temperature superconductivity in pure or doped $$Fm\bar{3}m$$ F m 3 ¯ m -LuH3, if confirmed, cannot be explained by a conventional electron-phonon mediated pairing mechanism.

Strategies for improving the superconductivity of hydrides under high pressure

“…The findings contribute to a better understanding of the superconducting behavior of hydrides at high pressures and suggest a pathway for enhancing superconductivity in hydrogen-based materials. Recently, Lucrezi et al presented a comprehensive analysis of the impact of quantum fluctuations and anharmonic corrections on the superconducting properties of lutetium trihydride at high pressures [165]. By incorporating temperature and quantum anharmonic effects, the study reveals that the structural instability of Fm-3m-LuH 3 phase predicted at ambient pressure is suppressed at temperatures above 200 K. The research further employs the Migdal-Eliashberg formalism to determine the T c for electron-phonon mediated superconductivity, finding T c to be in the range of 50-60 K, which is below the stability threshold, indicating that room-temperature superconductivity in LuH 3 is unlikely via conventional EPC.…”

Novel ground state structures of N-doped LuH3

“…So far most of the experiments, except [11]. Where some evidences of superconductivity were reported, have failed to reproduce the superconductivity [12][13][14][15][16][17][18] and DFT based calculations [19][20][21][22][23][24][25][26][27] also could not explain the observed superconductivity by using conventional mechanism.…”