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Register a new userField-effect induced superconductivity in surfaces of tetrahedrally coordinated semiconductors: the case of (111) hydrogenated silicon
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Davide Romanin
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We show the possibility of inducing a superconductive phase transition in tetrahedrally coordinated semiconductors via field-effect (FET) doping by taking as an example the hydrogenated (111) silicon surface. We perform density functional theory computations of the electronic and vibrational properties of the system in the proper FET geometry, by taking into account the applied electric field and the induced charge density. Using a simplified superconductive model at $q=Gamma$ and the McMillan/Allen-Dynes formula, we get an estimate of the superconductive critical temperature. We observe that, by heavily doping with holes at $n_{dop}=6cdot10^{14}$ cm$^{-2}$, we get an electron-phonon coupling constant of $lambda_{Si}=0.98$ and a superconductive phase transition at $T_{text{c}}in[8.94;10.91]$ K, with $mu^*in[0.08;0.12]$.
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We perform single- and multi-band Migdal-Eliashberg (ME) calculations with parameters exctracted from density functional theory (DFT) simulations to study superconductivity in the electric-field-induced 2-dimensional hole gas at the hydrogenated (111) diamond surface. We show that according to the Eliashberg theory it is possible to induce a high-T$_{text{c}}$ superconducting phase when the system is field-effect doped to a surface hole concentration of $6times10^{14},$cm$^{-2}$, where the Fermi level crosses three valence bands. Starting from the band-resolved electron-phonon spectral functions $alpha^2F_{jj}(omega)$ computed ab initio, we iteratively solve the self-consistent isotropic Migdal-Eliashberg equations, in both the single-band and the multi-band formulations, in the approximation of a constant density of states at the Fermi level. In the single-band formulation, we find T$_{text{c}}approx40,$K, which is enhanced between $4%$ and $8%$ when the multi-band nature of the system is taken into account. We also compute the multi-band-sensistive quasiparticle density of states to act as a guideline for future experimental works.
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