Scaling between Superfluid Density and <i>T</i>_c in Overdoped La_2−<i>x</i>Sr_<i>x</i>CuO₄ Films

Abstract

We used an electronic phase separation approach to interpret the scaling between the low-temperature superfluid density average ρ sc ( 0 ) and the superconducting critical temperature T c on overdoped La 2 − x Sr x CuO 4 films. Guided by the observed nematic and incommensurate charge ordering (CO), we performed simulations with a free energy that reproduces charge domains with wavelength λ C O and provides a scale to local superconducting interactions. Under these conditions a complex order parameter with amplitude Δ d ( r i ) and phase θ ( r i ) may develop at a domain i. We assumed that these domains are coupled by Josephson energy E J ( r i j ) , proportional to the local superfluid density ρ sc ( r i j ) . Long-range order occured when the average E J ( T c ) is ∼ k B T c . The linear ρ s c ( 0 ) vs. T c relation was satisfied whenever CO was present, even with almost vanishing charge amplitudes.

Keywords

• cuprate supercondutores
• electronic phase separation
• superfluid density
• Josephson effects