Temperature dependent giant resistance anomaly in LaAlO3/SrTiO3 nanostructures

Abstract

The resistance of the electron gas (2DEG) 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 a 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.

Anisotropic magnetotransport in LaAlO$_3$/SrTiO$_3$ nanostructures

“…In 2017 Goble et al demonstrated that the resistivity perpendicular to a domain wall is higher [12] than along the domain wall. Almost at the same time Minhas et al [13] showed an even more drastic effect on transport in LAO/STO nanostructures. They observed a resistance peak in 100nm wide LAO/STO channels around the phase transition temperature when warming up the structure.…”

“…The origin of the anomaly is often linked to structural phase transitions in the STO [9][10][11][12] but also alternative explanations were discussed [8]. In 2017 Minhas et al [13] showed that the resistance anomaly can also be observed in material grown at high oxygen pressure when a lateral confinement in a nanostructure exists.…”

Strain-induced conductivity accelerated recoveries in LaAlO3/SrTiO3 heterostructure with millimeter scale

“…The trapped single-vacancies and divacancies become mobile above 80 K and 176 K, which yields the conductivity recovery, separately. The reported cases 28,[32][33][34] are the patterned few layers LAO/STO in the length scale less than 10 mm, which means the interface is fully strained. When the number of LAO layers increases, the sample changes from fully strained state to partial strained state.…”

“…Because this two novel points are of the precise temperature interval it provides a potential temperature standard reference in the region of low temperature based on its resistance measurement and can be widely applied due to its larger scale. Minhas et al 34 made nano-patterned 6 u.c. layers LAO/STO samples and observed giant resistance anomaly.…”

Manifold field effects at a complex oxide interface

“…Because this elongation is equally likely to occur along the x, y, or z axis, domains of differently oriented tetragonal unit cells emerge. These domains, and especially the walls forming between them, may have profound consequences for conductivity at SrTiO 3 surfaces (41)(42)(43)(44)(45)(46)(47). In the work described in this thesis, we find that two-dimensional models for conductivity apply to the data very well: the effect of these domain walls on our experiments appears to be negligible.…”