Temperature dependent giant resistance anomaly in LaAlO3/SrTiO3 nanostructures

TL;DR

Nanostructuring LAO/STO interfaces reveals temperature-dependent resistance peaks linked to phase transitions and filament dynamics, challenging previous assumptions based on larger structures.

Contribution

This study uncovers a novel temperature anomaly in nanostructured LAO/STO interfaces caused by filament formation and phase transitions, which was not observed in larger structures.

Findings

Resistance peaks between 50 and 100 K in nanostructures

Filament formation at domain walls during cooling

Complete conductance loss during warm-up due to filament interruption

Abstract

The resistance of the electron gas at the interface between the two band insulators LaAlO3 (LAO) and SrTiO3 (STO) typically drops monotonically with temperature and R/T curves during cooling and warm-up look identical for large area structures. Here we show that if the LAO/STO is laterally restricted by nanopatterning the resistance exhibits a temperature anomaly. Warming up nanostructures from low temperatures leads to one or two pronounced resistance peaks between 50 and 100 K not observed for larger dimensions. During cool-down current filaments emerge at the domain walls that form during the well-known structural phase transition of the STO substrate. During warm-up the reverse phase transition can interrupt filaments before the sheet conductivity which dominates at higher temperature is reestablished. Due to the limited number of filaments in a nanostructure this process can result in a complete loss of conductance. As a consequence of these findings the transport physics extracted from experiments in small and large area LAO/STO structures may need to be reconsidered.