Superconducting properties of Fibonacci chains with enhanced superconducting pairing at the boundaries

TL;DR

This paper investigates the unique superconducting behavior at the ends of Fibonacci quasicrystals, revealing enhanced critical temperatures due to topological and critical state interactions, with potential implications for increasing superconductivity.

Contribution

It demonstrates the existence of universal end superconductivity and identifies two distinct critical temperatures in Fibonacci chains, highlighting the role of topological states in superconducting enhancement.

Findings

End superconductivity persists at higher temperatures than the bulk critical temperature.

Maximum enhancement of the right end's critical temperature reaches 66%.

Distinct critical temperatures are observed at the two ends of the chain.

Abstract

Recently, the superconducting properties of Fibonacci quasicrystals have attracted considerable attention. By numerically solving the self-consistent Bogoliubov-de Gennes equations for an $s-$wave superconducting Fibonacci chain, we find that the system exhibits universal end superconductivity, where the pair potential at the chain ends can persist at higher temperatures compared to the bulk critical temperature ($T_{cb}$) of the condensate in the chain center. Furthermore, our study reveals two distinct critical temperatures at the left ($T_{cL}$) and right ($T_{cR}$) ends of the chain. This complex behavior arises from the competition between topological bound states and critical states, a characteristic of quasicrystals. With the chosen parameters, the maximal enhancement of $T_{cR}$ reaches up to $66\%$ relative to $T_{cb}$, while $T_{cL}$ can increase by up to $31\%$. Our study sheds light on the phenomenon of end superconductivity in Fibonacci quasicrystals, pointing to alternative pathways for increasing the superconducting critical temperature.