Perspective: strain and strain gradient engineering in membranes of quantum materials

TL;DR

This paper discusses how free-standing membranes of quantum materials can be engineered with large, tunable strains and strain gradients to induce novel electronic, magnetic, and topological phases, expanding beyond traditional epitaxial methods.

Contribution

It introduces membrane-based strain engineering as a versatile approach for inducing new phases in quantum materials, overcoming limitations of small, uniform strains in bulk and epitaxial films.

Findings

Membranes enable large, tunable strains (~10%) and strain gradients.

Strain gradients can activate polar distortions and topological states.

Recent synthesis advances allow extreme strains in non-vdW materials.

Abstract

Strain is powerful for discovery and manipulation of new phases of matter; however, the elastic strains accessible to epitaxial films and bulk crystals are typically limited to small ($<2\%$), uniform, and often discrete values. This Perspective highlights new directions for strain and strain gradient engineering in free-standing single crystalline membranes of quantum materials. Membranes enable large ($\sim 10\%$), continuously tunable strains and strain gradients via bending and rippling. Moreover, strain gradients break inversion symmetry to activate polar distortions, ferroelectricity, chiral spin textures, novel superconductivity, and topological states. Recent advances in membrane synthesis by remote epitaxy and sacrificial etch layers enable extreme strains in new materials, including transition metal oxides and Heusler compounds, compared to natively van der Waals (vdW) materials like graphene. We highlight new opportunities and challenges for strain and strain gradient engineering in membranes of non-vdW materials.