Specific heat and electronic states of superconducting boron-doped silicon carbide

Abstract

The discoveries of superconductivity in the heavily-boron doped semiconductors diamond 1 (C:B) in 2004 and silicon 2 (Si:B) in 2006 have renewed the interest in the physics of the superconducting state of doped semiconductors. Recently, we discovered superconductivity in the closely related "mixed" system heavily boron-doped silcon carbide (SiC:B).3 Interestingly, the latter compound is a type-I superconductor whereas the two aforementioned materials are type-II. In this paper we present an extensive analysis of our recent specific-heat study, as well as the band structure and expected Fermi surfaces. We observe an apparent quadratic temperature dependence of the electronic specific heat in the superconducting state. Possible reasons are a nodal gap structure or a residual density of states due to non-superconducting parts of the sample. The basic superconducting parameters are estimated in a Ginzburg-Landau framework. We compare and discuss our results with those reported for C:B and Si:B. Finally, we comment on possible origins of the difference in the superconductivity of SiC:B compared to the two "parent" materials C:B and Si:B.

Superconductivity in carrier-doped silicon carbide

“…Table 1 lists preliminary specific heat coefficients γ n [38]; basic normal-state parameters: Fermi wave number k F , effective mass m * , Fermi velocity v F , mean free path l; as well as superconducting state parameters: penetration depth λ, coherence length ξ and Ginzburg-Landau parameter κ GL . Those parameters were estimated as described in [39]. For comparison, the previously reported parameters for 3C-SiC:B, C:B and Si:B are added.…”

Characterization of neutral boron-silicon clusters using infrared spectroscopy: The case of Si6B

“…With the discovery of a superconducting transition at about 40 K in MgB2 [10], there has been great interest in boron-doped materials as promising superconductors, including boron-doped diamond [11,12], silicon [13], and silicon carbide [14][15][16]. In crystalline phases, doping of group IV elements with boron as the source of holedoping has been shown to induce superconductivity [12,13,17].…”

Superconductivity in heavily boron-doped silicon carbide

“…The two relevant modifications for this paper are 3C-and 6H-SiC shown in figure 1. For a more comprehensive introduction to SiC see [11] and references therein. We note here that all SiC polytypes break inversion symmetry which is known to give rise to quite unconventional superconducting scenarios, e. g. in heavy-fermion compounds, in contrast to the inversion-symmetry conserving systems C : B and Si : B.…”