Electronic Structure of Novel Superconductor AuSb6Te

Some elements show valence-skipping behavior, e.g. Bi takes 3+ and 5+ valences but scarcely takes 4+ valence. This means that the effective interaction Ueff=2E(Bi 4+ )-E(Bi 3+ )-E(Bi 5+ ) is negative. This situation naturally leads to the so-called negative-U model[1], and the superconductivity in (Ba,K)BiO3 and Tl:PbTe was attributed to this mechanism[2,3]. Varma has firstly tackled this problem and consecutive works are revealing the mechanism of this valence-skipping behavior [2,4,5]. Apart from the quantitative estimation of |Ueff|, this concept may be useful to search new superconductors. From this concept we have found a new superconductor AuSb6Te[6]. This compound was known to be a semiconductor[7], but our research has clarified that this compound is a superconductor with Tc=6.7K. In order to investigate the mechanism of the superconductivity in this new material, it is necessary to know the precise band structure. In this paper, we have performed an ab-initio band structure calculation for AuSb6Te. Section 2 describes the framework of our calculation. The results and discussions are developed in §3. A brief summary is shown in §4.