Fermi surface topology and anisotropic superconducting gap in electron-doped hydride compounds at high pressure

Abstract

The recent theoretical discovery of the predicted high-temperature superconductivity (superconducting transition temperature Tc∼351K at 300 GPa) in clathrate Li2MgH16 is an important advance toward room-temperature superconductors. Here we use first-principle approaches to identify a new ternary hydride of clathrate structure of Fd3¯m−Rb2MgH16 by Rb-doped MgH16 at 300 GPa. We first verified the thermal and dynamic stability for the Fd3¯m−Rb2MgH16 through the formation enthalpy and phonon calculations, respectively. Next, we showcased that Fd3¯m−Rb2MgH16 has two Fermi surface (FS) sheets, which are both dominated by the H2 s orbital. Using the Eliashberg formalism, the Tc of Fd3¯m−Rb2MgH16 was calculated to be 130 K at 300 GPa. Furthermore, the calculations of the electronic, phonon, and superconducting properties reveal that Fd3¯m−Li2MgH16 has four FS sheets with mixed H1 s and H2 s orbital character and reaches the Tc of 352 K at 300 GPa. Compared with Fd3¯m−Rb2MgH16, Fd3¯m−Li2MgH16 produces high-frequency phonon softening, leading to the enhancement of Tc. Moreover, it is demonstrated that Rb substitution for Li produces the reduction of contribution of H orbitals to the FS sheets and the decrease in FS sheets in number, which tend to decrease the electron-phonon coupling strength and Tc. Our observed FS sheets and their associated superconducting gap will provide key insights into the understanding of the superconductivity mechanism in these and related systems.

Source-reported materials — not catalogue approval

Similar papers