Polarity and anti-distortive polarons in WO3 through epitaxial shear strain
- Ewout van der Veer
- Martin F. Sarott
- Jack T. Eckstein
- Stijn Feringa
- Dennis van der Veen
- Johanna van Gent González
- Majid Ahmadi
- Horatio R. J. Cox
- Ellen M. Kiens
- Gertjan Koster
- Bart J. Kooi
- Michael A. Carpenter
- Ekhard K. H. Salje
- Beatriz Noheda
2026-07-13
Bestowing complementary metal-oxide semiconductor-compatible binary oxides with additional functionalities is a powerful strategy toward the realization of oxide electronics. Ideal candidates are thin films which display a strong sensitivity to strain, chemical doping or nanoscale confinement. Among these, crystalline tungsten trioxide WO 3 exhibits exceptional structural flexibility, enabling a wide range of functionalities. Here we reveal the emergence of a polar phase in epitaxial WO 3 thin films. We accomplish this by imposing epitaxial shear strain, which stabilizes a low-symmetry triclinic structure that persists up to large film thicknesses and elevated temperatures. At the atomic scale, a change in the oxygen octahedral tilt pattern facilitates this symmetry lowering into a polar phase, which manifests as a periodic in-plane polarized stripe domain configuration with needle-like bifurcations at the microscale. The stripe domain walls further exhibit a strongly enhanced electrical conductivity in conjunction with a pronounced reduction of a distortive structural mode, providing experimental evidence for anti-distortive polaronic transport recently predicted in WO 3 .