Synopsis

Flexing an Electron Gas

Physics 12, s74
Bending a stack of metal oxide sheets can alter the electrical resistance of a 2D electron gas that resides within.
F. Zhang et al., Phys. Rev. Lett. (2019)

Flexoelectricity is a polarization that occurs in insulators when they are bent or stretched in a nonuniform way. The effect is usually small, but recent work has explored using it in certain photovoltaic materials. Now researchers have shown that flexing a metal oxide structure—consisting of a lanthanum aluminate (LAO) film above a strontium titanate (STO) substrate—can alter the resistance of a 2D electron gas trapped between the layers. This flexoelectric effect might be useful in future energy-harvesting devices or mechanical sensors.

Thanks to their compact nature and ultralow resistance, 2D electron gases are attractive for electronic device applications. The electron gas in LAO/STO structures is especially interesting, as it exhibits superconductivity and ferromagnetism (see 25 July 2011 Viewpoint). Previous work has shown that the electronic properties of LAO/STO are sensitive to various inputs, such as light and spin-polarized currents. Flexoelectricity offers a new “handle” for manipulating the LAO/STO system.

Ji-yan Dai from The Hong Kong Polytechnic University and colleagues bent an LAO/STO structure while monitoring the resistance through the electron gas. They discovered that the resistance in the gas increased by as much as 3% when the structure’s edges were bent down, forming a “hill” shape. Flexing the sample in a “valley” shape decreased the resistance by as much as 0.3%. The team showed that these resistance changes were caused by flex-induced polarization in the thin film of LAO. The electric field from this polarization altered the resistance in the electron gas by driving electrons into or out of the LAO/STO interface, depending on the flex orientation.

This research is published in Physical Review Letters.

–Michael Schirber

Michael Schirber is a Corresponding Editor for Physics based in Lyon, France.


Subject Areas

Condensed Matter Physics

Related Articles

Building Novel Carbon Allotropes
Condensed Matter Physics

Building Novel Carbon Allotropes

Calculations indicate that a form of carbon synthesized from pentagonal hydrocarbon molecules could have unusual electrical and mechanical properties. Read More »

Defect or No Defect: It’s a Toss Up
Cosmology

Defect or No Defect: It’s a Toss Up

A theoretical study of phase transitions reveals new universal nonequilibrium features in the statistics of topological defects. Read More »

Postponing Heat Death in Periodically Driven Systems
Condensed Matter Physics

Postponing Heat Death in Periodically Driven Systems

An exponential suppression of heating has been observed in a periodically driven optical lattice, opening up an opportunity to engineer new states of matter. Read More »

More Articles