Indications of an Electronic Phase Transition in 2D YBa2Cu3O7-x Induced by Electrostatic Doping

TL;DR

This study demonstrates reversible electrostatic doping of ultrathin YBa2Cu3O7-x films, revealing anomalous transport behaviors and evidence of an electronic phase transition in the Fermi surface near optimal doping.

Contribution

It introduces a reversible electrostatic doping method for ultrathin YBa2Cu3O7-x films and uncovers unique doping mechanisms and phase transition signatures not seen in bulk samples.

Findings

Normal resistance increases with doping on the overdoped side

Hall number peaks at doping level p~0.15

Evidence of an electronic phase transition in the Fermi surface

Abstract

We successfully tuned an underdoped ultrathin YBa2Cu3O7-x film into the overdoped regime by means of electrostatic doping using an ionic liquid as a dielectric material. This process proved to be reversible. Transport measurements showed a series of anomalous features compared to chemically doped bulk samples and a different two-step doping mechanism for electrostatic doping was revealed. The normal resistance increased with carrier concentration on the overdoped side and the high temperature (180 K) Hall number peaked at a doping level of p$\sim$0.15. These anomalous behaviors suggest that there is an electronic phase transition in the Fermi surface around the optimal doping level.