Nanoscience Perspective on Disorder Modifications of Superconducting Critical Temperature

TL;DR

This paper explores how disorder, introduced via impurities, can potentially increase the superconducting critical temperature, especially in nanoscience contexts, by reexamining classical theories with modern quantum many-body techniques.

Contribution

It provides a new analytical formula for the critical temperature incorporating disorder effects, using advanced quantum Green's function methods relevant to nanoscience.

Findings

Disorder can enhance superconducting critical temperature.

Reexamination of classical theories with modern quantum methods.

Analytical formula relating disorder to critical temperature.

Abstract

Superconductivity can be modified by various effects related to randomness, disorder, structural defects, and other similar physical effects. Their affects on superconductivity are important because such effects are intrinsic to certain material system's preparation, or may be intentionally produced. In this work we show in the context of a Cooper instability relationship, that introduction of disorder through impurities could possibly lead to an increase in critical temperature. This is an old subject, having been addressed decades ago in the view of simpler substances, including metal alloy materials. Today, with the advances in material science, nanoscience, and atomic level preparation of materials and devices, this subject should be reexamined. That is our purpose here, especially in light of some recent discoveries made in the area of the metal-insulator transition, to be covered herein. One may obtain a formula for the critical temperature which is recognizable, and relatable to Bardeen-Cooper-Schrieffer theory, by using many-body quantum theory for condensed matter expeditiously, using quantum Green's functions, polarization functions (correlation functions), and vertex functions, to extract out an analytical formula for critical temperature. The reader will find use made of perturbational Feynman diagrammatic techniques, finite temperature Matsubara Green's functions, and quantum perturbational derivations without the diagrams.