We present a combined growth and transport study of superconducting single-crystalline NdO0.5F0.5BiS2. Evidence of two-dimensional superconductivity with significant phase fluctuations of preformed Cooper pairs preceding the superconducting transition is reported. This result is based on three key observations. (1) The resistive superconducting transition temperature Tc (defined by resistivity ρ→0) increases with increasing disorder. (2) As T→Tc, the conductivity diverges significantly faster than what is expected from Gaussian fluctuations in two and three dimensions. (3) Non-Ohmic resistance behavior is observed in the superconducting state. Altogether, our observations are consistent with a temperature regime of phase-fluctuating superconductivity. The crystal structure with magnetic ordering tendencies in the NdO0.5F0.5 layers and (super)conductivity in the BiS2 layers is likely responsible for the two-dimensional phase fluctuations. As such, NdO0.5F0.5BiS2 falls into the class of unconventional ``laminar" bulk superconductors that include cuprate materials and 4Hb-TaS2.
@article{arxiv.2401.16980,
title = {Two-Dimensional Phase-Fluctuating Superconductivity in Bulk-Crystalline NdO$_{0.5}$F$_{0.5}$BiS$_2$},
author = {C. S. Chen and J. Küspert and I. Biało and J. Mueller and K. W. Chen and M. Y. Zou and D. G. Mazzone and D. Bucher and K. Tanaka and O. Ivashko and M. v. Zimmermann and Qisi Wang and Lei Shu and J. Chang},
journal= {arXiv preprint arXiv:2401.16980},
year = {2024}
}