Localization and Superconductivity in Doped Semiconductors

Abstract

Motivated by the discovery of superconductivity in boron-doped (B-doped) diamond, we investigate the localization and superconductivity in heavily doped semiconductors. The competition between Anderson localization and s-wave superconductivity is investigated from the microscopic point of view. The effect of microscopic inhomogeneity and the thermal fluctuation in superconductivity are taken into account using the self-consistent 1-loop-order theory with respect to superconducting fluctuation. The crossover from superconductivity in the host band to that in the impurity band is described on the basis of the disordered three-dimensional attractive Hubbard model for binary alloys. We show that superconductor-insulator transition (SIT) accompanies the crossover. We point out an enhancement of Cooper pairing in the crossover regime. Further localization of the electron wave function gives rise to incoherent Cooper pairs and the pseudogap above Tc. A global phase diagram is drawn for host band superconductivity, impurity band superconductivity, Anderson localization, Fermi liquid state, and pseudogap state. A theoretical interpretation is proposed for superconductivity in the doped diamond, SiC, and Si.

Unconventional superconductivity in electron-doped layered metal nitride halides MNX (M= Ti, Zr, Hf; X= Cl, Br, I)

“…Regarding the T c enhancement in the lightly doped regime, apart from the microscopic pairing mechanism, the system approaching the Anderson localization may be playing some role in the enhancement of T c , as suggested by several authors [44,[72][73][74]. The Anderson localization scenario may also account for the absence of the coherence peak [44].…”

Superconducting group-IV semiconductors

“…Note that, in the dirty limit when the mean free path l is much smaller than the coherence length ξ, κ (=λ L /ξ) is renormalized to λ L /l, λ L being the London penetration depth and a clean type I superconductor (κ<0.7) might be turned into a dirty type II superconductor. e) Another fundamental aspect in superconducting semiconductors is the new playground it offers for studying the interplay of disorder-induced localization, Coulomb interaction and superconductivity in the vicinity of a disorder-driven Mott-Anderson transition [97,98] (see Box 2). For instance, T C remains anomalously high down to the transition in boron doped diamond [99] whereas, in the BCS picture, it is expected to become exponentially small as λ ep tends towards zero at the MIT.…”

Strong suppression of coherence effect and appearance of pseudogap in the layered nitride superconductorLixZrNCl:Zr91- andKotegawa1, Oshiro2, Shimizu3 et al. 2014Phys. Rev. B133150View full textAdd to dashboardCite

“…The second candidate is a scenario whereby T c is enhanced by Anderson localization in the lightly doped region [31][32][33][34]. It has been pointed out that the fractal (inhomogeneous) wave function affected by randomness near the Anderson transition can enhance the pairing interaction on the site contributing to conductivity in the s-wave framework.…”