Probing an excitonic insulator

Abstract

Physics In semiconductors and semimetals, the negatively charged electrons and positively charged holes carry electrical current by moving in opposite directions. However, if electrons and holes were to form electrically neutral pairs, the material might stop conducting electricity and become an (excitonic) insulator. Du et al. explored this possibility in InAs/GaSb quantum wells, where electrons reside in the InAs layer and holes in the GaSb layer. Transmission spectroscopy in combination with transport measurements revealed the presence of an energy gap, which responded to the application of a magnetic field as one would theoretically expect for an excitonic insulator. The topologically nontrivial band structure of this system indicates that it might be a topological excitonic insulator. Nat. Commun. 10.1038/s41467-017-01988-1 (2017).