A room-temperature ferroelectric semimetal

Ferroelectricity has often been associated with and observed in materials that are insulating or semiconducting rather than metallic because conduction electrons in metals screen out the static internal fields arising from a long-range dipolar order. In the 1960s, Anderson and Blount proposed materials with these seemingly incompatible characteristics, i.e., metals with a polar axis termed ferroelectric metals. Since then, ferroelectric metals were merely a theoretical construct until recent experimental observations suggesting otherwise. Despite the progress, electrically switchable intrinsic electric polarization, together with the direct observation of ferroelectric domains, has not yet been realized in a bulk crystalline metal, although incomplete screening by mobile conduction charges should, in principle, be possible.
Here, we provide evidence that native metallicity and ferroelectricity coexist in bulk crystalline van der Waals WTe₂. We show that, despite being a Weyl semimetal, WTe₂ has switchable spontaneous polarization and a natural ferroelectric domain structure at room temperature. This new class of materials has tantalizing potential for functional nanoelectronics applications.