Ferroelectricity in van der Waals materials usually comes from lattice distortions, layer sliding or moiré reconstruction. Researchers at Aalto University show that it can also arise directly from electron interactions. Using molecular beam epitaxy, scanning tunnelling microscopy and ab initio calculations, they studied two stackings of bilayer 1T-TaSe2, in which 'Star-of-David' charge-density-wave clusters form quasi-one-dimensional chains.
In one stacking, strong interlayer hybridisation produces a band insulator. In the other, Coulomb interactions between the layers cause a spontaneous charge imbalance and an out-of-plane ferroelectric polarisation, and ferroelectric and antiferroelectric configurations can be switched with an electric field. The work combines Peter Liljeroth's Atomic Scale Physics group with QMAT's Correlated Quantum Materials group, including Ana Vera Montoto, Jose Lado and Adolfo Fumega.
The preprint has not yet been peer reviewed.
Image: QMAT