Evidence of Two-Dimensional Quantum Critical Behavior in the Superfluid Density of Deeply Underdoped Bi2Sr2CaCu2O8+x

TL;DR

This paper presents evidence of two-dimensional quantum critical fluctuations influencing the superfluid density in underdoped Bi-2212, highlighting the role of quantum fluctuations in cuprate superconductors and contrasting with three-dimensional behavior in less anisotropic materials.

Contribution

It demonstrates 2D quantum critical behavior in the superfluid density of deeply underdoped Bi-2212, revealing the dominance of quantum fluctuations in these cuprates.

Findings

2D quantum critical fluctuations observed in superfluid density

Linear scaling between Tc and superfluid density at zero temperature

Contrast between 2D behavior in Bi-2212 and 3D in YBCO

Abstract

Evidence of two-dimensional (2D) quantum critical fluctuations is observed in the superfluid density ns(T) \propto $\lambda$ -2(T) of deeply underdoped Bi2Sr2CaCu2O8+x (Bi-2212) films, indicating that quantum fluctuations play a dominant role in underdoped cuprates in general. 2D fluctuations are expressed by the linear scaling, Tc \propto ns(0). 2D scaling in Bi-2212 contrasts with 3D scaling seen in the much less anisotropic YBa2Cu3O7-x. Quantum critical fluctuations could also account for the absence of thermal critical behavior in \lambda^{-2}(T) of strongly underdoped Bi-2212 samples, Tc < 48 K.