?
Superconducting properties of Fibonacci chains with enhanced superconducting pairing at the boundaries
Recently, the superconducting properties of Fibonacci quasicrystals have attracted considerable attention. By numerically solving the self-consistent Bogoliubov-de Gennes equations for a Fibonacci chain under superconducting proximity, 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 end (T_cL) and right end (T_cR), governing the superconducting condensate at the chain ends. This complex behavior arises from the competition between topological bound states and critical states, a characteristic of quasicrystals. Due to the geometric configuration of Fibonacci chain approximants, T_cL and T_cb are independent of the Fibonacci sequence number n, while T_cR significantly depends on the parity of n. With the chosen parameters, the maximal enhancement of T_cR occurs for even n, reaching up to 50 % relative to T_cb, while T_cL can increase by up to 23 %. Our study sheds light on the phenomenon of end superconductivity in Fibonacci quasicrystals, pointing to alternative pathways for discovering materials with higher superconducting critical temperatures.