Superconductivity in doped semiconductors

Abstract

International audienceA historical survey of the main normal and superconducting state properties of several semiconductors doped into superconductivity is proposed. This class of materials includes selenides, tellurides, oxides and column-IV semiconductors. Most of the experimental data point to a weak coupling pairing mechanism, probably phonon-mediated in the case of diamond, but probably not in the case of strontium titanate, these being the most intensively studied materials over the last decade. Despite promising theoretical predictions based on a conventional mechanism, the occurrence of critical temperatures significantly higher than 10 K has not been yet verified. However, the class provides an enticing playground for testing theories and devices alike

Superconductivity in single-crystalline aluminum- and gallium-hyperdoped germanium

“…After hyperdoping the TO phonon mode of Ge-Ge vibrational is shifted down to 288.2 cm -1 for the Al doped sample and down to 281.9 cm -1 for the Ga doped Ge. This is very close to the theoretically predicted values for the high frequency 13 of the zone-center optical mode in hyperdoped Ge (about 278 cm -1 ). The shift of the TO phonon mode in ultra-high doped Ge and the peak asymmetry is due to the phonon softening and the Fano effect [42][43][44].…”

Plasmon Effect on the Coulomb Pseudopotential μ* in the McMillan Equation

“…As shown in Fig.1(b), it indicates that n-dependences of T c obtained by theory are far from that of experiments, even if we use negative µ * . [25] As long as a constant µ * is adopted to Eq.1, it is difficult to explain n-dependences of T c . This result suggests that we need to change the traditional interpretation of µ * .…”

Fluctuation spectroscopy as a probe of granular superconducting diamond films

“…The phenomenon was quickly demonstrated in both single-crystalline [9] and polycrystalline [10] diamond synthesised by chemical vapour deposition (CVD). While superconductivity in doped semiconductor materials [11,12] is an active area of research, and although nanocrystalline diamond retains many of the desirable mechanical properties of single-crystalline material [13], a sometimes overlooked property in the study of superconductivity in polycrystalline boron-doped diamond is the physical granularity itself.A clear experimental signature of superconducting granular systems, as pointed out by Lerner, Varlamov and Vinokur [5] (henceforth referred to as LVV), is that there are three distinct temperature regimes in the vicinity of the critical temperature (T c ), distinguished by the magnitude of the temperature-dependent GinzburgLandau coherence length. At temperatures immediately above T c , short-lived Cooper pairs act as charge carriers, modifying the conductivity.…”

“…The phenomenon was quickly demonstrated in both single-crystalline [9] and polycrystalline [10] diamond synthesised by chemical vapour deposition (CVD). While superconductivity in doped semiconductor materials [11,12] is an active area of research, and although nanocrystalline diamond retains many of the desirable mechanical properties of single-crystalline material [13], a sometimes overlooked property in the study of superconductivity in polycrystalline boron-doped diamond is the physical granularity itself.…”