Superconducting Behavior in Compressed Solid ${\mathrm{SiH}}_4$ with a Layered Structure

The electronic and lattice dynamical properties of compressed solid ${\mathrm{SiH}}_4$ have been calculated in the pressure range up to 300 GPa with density functional theory. We find two energetically preferred insulating phases with $P{2}_1/c$ and $Fdd2$ symmetries at low pressures. We demonstrate that the $Cmca$ structure having a layered network is the most likely candidate of the metallic phase of ${\mathrm{SiH}}_4$ over a wide pressure range above 60 GPa. The superconducting transition temperature in this layered metallic phase is found to be in the range of 20–75 K.

Figure 1

The enthalpy versus pressure for competitive structures of ${\mathrm{SiH}}_4$. The enthalpy of the $I{4}_1/a$ phase is taken as the reference point.

Figure 2

The energetically most favorable structures computed for ${\mathrm{SiH}}_4$ polymorphs at various pressures.

Figure 3

(a) Electronic band structure for the $Cmca$ ${\mathrm{SiH}}_4$ phase at 250 GPa. The horizontal line shows the location of the Fermi level. (b) The phonon dispersion and phonon density of states (PDOS) projected on Si and H atoms for the $Cmca$ ${\mathrm{SiH}}_4$ at 250 GPa.

Figure 4

Electron-phonon spectral function ${\alpha }^{2}F(\omega )$ versus frequency $\omega$ of the $Cmca$ ${\mathrm{SiH}}_4$ at pressures.

Figure 5

Calculated (a) logarithmic average phonon frequency ${\omega }_{\log }$, (b) electron-phonon coupling parameter $\lambda$, and (c) superconducting transition temperature $T_c$ of the $Cmca$ phase of metallic ${\mathrm{SiH}}_4$ as a function of pressure.