Scanning tunneling spectroscopy characterization of the pseudogap and the x = 1/8 anomaly in La2-xSrxCuO4 thin films

TL;DR

This study uses scanning tunneling spectroscopy to analyze the local density of states in La2-xSrxCuO4 thin films, revealing doping-dependent pseudogap behavior and a unique zero bias conductance peak near x=1/8, unrelated to surface facets.

Contribution

It provides new insights into the local electronic states and the x=1/8 anomaly in La2-xSrxCuO4, highlighting a spectral feature not explained by surface orientation effects.

Findings

Pseudogap exists only below optimal doping.

A zero bias conductance peak appears near x=1/8 doping.

The peak is not due to tunneling into (110) facets.

Abstract

Using scanning tunneling spectroscopy we examined the local density of states of thin c-axis La2-xSrxCuO4 films, over wide doping and temperature ranges. We found that the pseudogap exists only at doping levels lower than optimal. For x = 0.12, close to the 'anomalous' x = 1/8 doping level, a zero bias conductance peak was the dominant spectral feature, instead of the excepted V- shaped (c-axis tunneling) gap structure. We have established that this surprising effect cannot be explained by tunneling into (110) facets. Possible origins for this unique behavior are discussed.