Charge Modulation at the Surface of High-T_c Superconductors

TL;DR

This paper investigates how surfaces of high-T_c superconductors develop dipole layers due to charge density modulation caused by suppressed gap functions, analyzed through Ginzburg-Landau and Gor'kov's equations.

Contribution

It provides a theoretical framework for understanding surface charge modulation in high-T_c superconductors considering boundary conditions from Gor'kov's equations.

Findings

Surface dipole layers are formed at high-T_c superconductor surfaces.

Charge modulation depends on boundary conditions derived from Gor'kov's equations.

The study discusses the impact of surface charging on the lens effect in superconducting films.

Abstract

It is shown here that surfaces of high-temperature superconductors are covered by dipole layers. The charge density modulation is induced by the local suppression of the gap function at the surface. This effect is studied in the framework of the Ginzburg-Landau theory and crucially depends on the appropriate boundary conditions. Those are derived from Gor'kov's equations for a d-wave pairing symmetry. Within this framework the structure of the surface dipole layer is determined. The contribution of this charging to a lens-effect of superconducting films with holes, which has been studied in recent experiments, is discussed.