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

C. S. Chen; J. Küspert; I. Biało; J. Mueller; K. W. Chen; M. Y. Zou; D. G. Mazzone; D. Bucher; K. Tanaka; O. Ivashko; M. v. Zimmermann; Qisi Wang; Lei Shu; J. Chang

doi:10.1103/PhysRevB.109.054516

paper

Two-Dimensional Phase-Fluctuating Superconductivity in Bulk-Crystalline NdO $_{0.5}$ F $_{0.5}$ BiS $_{2}$

arXiv:2401.16980 · doi:10.1103/PhysRevB.109.054516

Abstract

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 $ρ \to 0$ ) increases with increasing disorder. (2) As $T \to T_{c}$ , 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 $_{2}$ .

Two-Dimensional Phase-Fluctuating Superconductivity in Bulk-Crystalline NdO0.5​F0.5​BiS2​

Abstract

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Two-Dimensional Phase-Fluctuating Superconductivity in Bulk-Crystalline NdO $_{0.5}$ F $_{0.5}$ BiS $_{2}$