Core Size Effect on the Vortex Quasiparticle Excitations in Overdoped $L{a}_{2-x}S{r}_{x}Cu{O}_4$ Single Crystals

Abstract

Low temperature specific heat has been measured for an overdoped $L{a}_{2-x}S{r}_{x}Cu{O}_4$ (x = 0.22) single crystal. The quasiparticle density of states (DOS) in the mixed state is found to deviate from the predicted scaling law $C_{vol}=Hf(T/H^{1/2})$. However, this scaling behavior is nicely reconciled if one considers the normal core region ($\xi \approx$ 21$\mathring{A}$) which gives small contribution to the total DOS. The radius of the core and other parameters derived are consistent with reported values. Our results suggest that there is no zero-bias conductance peak (ZBCP), which is predicted by the simple Bogoliubov de-Gennes theory in the vortex core of a d-wave superconductor.

4 Pages, 4 Figures