Two-Dimensional Phase-Fluctuating Superconductivity in Bulk-Crystalline NdO\(_{0.5}\)F\(_{0.5}\)BiS\(_2\)

• Published in: arXiv.org 2024-02
• Main Authors: Chen, C S, Küspert, J, Biało, I, Mueller, J, Chen, K W, Zou, M Y, Mazzone, D G, Bucher, D, Tanaka, K, Ivashko, O, Zimmermann, M v, Wang, Qisi, Shu, Lei, Chang, J
• Format: Article
• Language: English
• Subjects: Cooper pairs; Crystal structure; Single crystals; Superconductivity; Superconductors; Transition temperature
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2401.16980

We present a combined growth and transport study of superconducting single-crystalline NdO\(_{0.5}\)F\(_{0.5}\)BiS\(_2\). 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 \(T_c\) (defined by resistivity \(\rho \rightarrow 0\)) increases with increasing disorder. (2) As \(T\rightarrow T_c\), 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 NdO\(_{0.5}\)F\(_{0.5}\) layers and (super)conductivity in the BiS\(_2\) layers is likely responsible for the two-dimensional phase fluctuations. As such, NdO\(_{0.5}\)F\(_{0.5}\)BiS\(_2\) falls into the class of unconventional ``laminar" bulk superconductors that include cuprate materials and 4Hb-TaS\(_2\).