Superconducting fluctuations in overdoped Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$

Abstract

Fluctuating superconductivity - vestigial Cooper pairing in the resistive state of a material - is usually associated with low dimensionality, strong disorder or low carrier density. Here, we report single particle spectroscopic, thermodynamic and magnetic evidence for persistent superconducting fluctuations in heavily hole-doped cuprate superconductor Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ ($T_c$ = 66~K) despite the high carrier density. With a sign-problem free quantum Monte Carlo calculation, we show how a partially flat band at ($\pi$,0) can help enhance superconducting phase fluctuations. Finally, we discuss the implications of an anisotropic band structure on the phase-coherence-limited superconductivity in overdoped cuprates and other superconductors.

main: 8 pages, 6 figures + supplement: 10 pages, 15 figures