Synopsis: Flexing an Electron Gas

Bending a stack of metal oxide sheets can alter the electrical resistance of a 2D electron gas that resides within.
Synopsis figure
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.


Features

More Features »

Announcements

More Announcements »

Subject Areas

Condensed Matter Physics

Previous Synopsis

Next Synopsis

Related Articles

Viewpoint: Graphene Is Thin, but Not Infinitely So
Condensed Matter Physics

Viewpoint: Graphene Is Thin, but Not Infinitely So

Atomically thin graphene is considered a prototypical 2D material, but high-pressure experiments now reveal the 3D nature of its mechanical properties. Read More »

Synopsis: Tinkering with Superconductivity in a Quasicrystal
Superconductivity

Synopsis: Tinkering with Superconductivity in a Quasicrystal

Quasicrystals might host an exotic superconducting phase when subjected to a magnetic field, according to a theoretical study. Read More »

Viewpoint: Questioning a Universal Law for Electron Attenuation
Materials Science

Viewpoint: Questioning a Universal Law for Electron Attenuation

A law describing electron attenuation in solids has long helped researchers determine the size of nanoscale objects, but experiments show that it is less general than previously thought. Read More »

More Articles