Phonon softening enhanced superconductivity in the YTiSi electride under pressure

Abstract

Electrides are a class of materials characterized by the localization of a portion of their electrons within specific interstitial regions, exhibiting properties akin to anions. In this study, we employed density functional theory calculations in conjunction with the Allen–Dynes modified McMillan equation to explore the electronic structure, lattice dynamics, and superconducting properties of the YTiSi electride. It is highlighted that YTiSi possesses localized interstitial electrons, confirming its zero-dimensional electride nature. Ab initio molecular dynamics simulations and phonon dispersion calculations demonstrate that YTiSi maintains its structural stability under moderate pressures. Notably, the application of external pressure leads to a significant increase in superconducting temperature (T_c), reaching a maximum value of 8.7 K at 36.8 GPa. The coupling between the in-plane atomic vibration modes and the electronic orbitals primarily dominates the electron–phonon coupling. Moreover, we unraveled that the physical origins of the pressure-induced superconductivity are the softening of the acoustic branches at the Z-point of the first Brillouin zone as well as the alterations in the electronic structures at the Fermi level. These findings not only elucidate the superconducting behavior of electride compounds but also hold promise for advancing quantum devices and high-efficiency electronic components through the application of external pressure.