Density functional Bogoliubov-de Gennes theory for superconductors implemented in the SIESTA code

TL;DR

SIESTA-BdG is a novel implementation combining Bogoliubov-de Gennes and DFT methods within the SIESTA code, enabling detailed simulations of both conventional and unconventional superconductors and their heterostructures.

Contribution

The paper introduces SIESTA-BdG, a first-principles computational tool that accurately models inhomogeneous superconductors using a unified BdG-DFT approach.

Findings

Accurate computation of superconducting properties for Nb, Pb, and FeSe.

Excellent agreement with experimental data and other computational methods.

Demonstrates efficiency and validity of the SIESTA-BdG implementation.

Abstract

We present SIESTA-BdG, an implementation of the simultaneous solution of the Bogoliubov-de Gennes (BdG) and Density Functional Theory (DFT) problem in SIESTA, a first-principles method and code for material simulations which uses pseudopotentials and a localized basis set. This unified approach describes both conventional and unconventional superconducting states, and enables a description of inhomogeneous superconductors and heterostructures. We demonstrate the validity, accuracy, and efficiency of SIESTA-BdG by computing physically relevant quantities (superconducting charge density, band structure, superconducting gap features, density of states) for conventional singlet (Nb, Pb) and unconventional (FeSe) superconductors. We find excellent agreement with experiments and results obtained within the KKR-BdG computational framework. SIESTA-BdG forms the basis for modelling quantum transport in superconducting devices and including - in an approximate fashion - the superconducting DFT potential of Oliveira, Gross, and Kohn.