An intrinsic model for strain tensor effects on the density of states in A15 Nb3Sn

Abstract

The superconducting critical properties of the intermetallic compound Nb3Sn are negatively affected by strain applied to the material, which is important for scientific and technological applications. A recent hydrostatic pressure experiment (Phys. Rev. B 95, 184503 (2017)) emphasized the importance of the density of states (DOS) at the Fermi surface in understanding the inherent electromechanical properties of superconducting Nb3Sn. The Nb3Sn material is subject to various strain states due to fabrication, thermal mismatch, and operation. Hence, a detailed description of the comprehensive study of the relationship between the DOS at the Fermi surface and different strain components must be established. In this paper, a model of the strain tensor effects on the DOS in an Nb3Sn compound with an A15 lattice structure is proposed on the basis of Bhatt’s model in combination with the k→·p→ perturbation theory results. The magnitudes of the principle strain components, together with the differences between the three quantities, intrinsically account for the diverse characteristics of the DOS at the Fermi level in Nb3Sn material undergoing different deformation patterns. The model is helpful for identifying the origin of the strain sensitivity in Nb3Sn, and developing microphysics-based strain scaling laws in practical Nb3Sn superconductors in multiple strain states.