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Critical Behaviour in the Spin Fluctuations and Superfluid Density of La$_{2-x}$Sr$_x$CuO$_4$

C. Panagopoulos·B. D. Rainford·J. R. Cooper·C. A. Scott·T. Xiang
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Abstract

We study the doping dependence of low frequency spin fluctuations and the zero-temperature superfluid density of La$_{2-x}$Sr$_x$CuO$_4$ using the muon spin relaxation ($μ$SR) and ac-susceptibility techniques. Superconductivity is found to coexist with low frequency spin fluctuations over a large region of the superconducting phase diagram. The characteristic temperature of spin fluctuations detected by $μ$SR decreases with increasing $x$ and vanishes above a critical doping $x_c\sim 0.19$. This value of $x_c$ coincides with the doping at which the normal state pseudogap extrapolates to zero. The superfluid density behaves in the opposite way to the low frequency spin fluctuations. It increases with $x$ and becomes nearly doping-independent for $x>x_c$. These results are consistent with predictions involving quantum criticality at $x_c$.

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C. Panagopoulos, B. D. Rainford, J. R. Cooper, C. A. Scott, T. Xiang. 2001-03-09. Critical Behaviour in the Spin Fluctuations and Superfluid Density of La$_{2-x}$Sr$_x$CuO$_4$. https://arxiv.org/abs/cond-mat/0007158

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