Engineering Dirac Materials: Metamorphic InAsSb/InAsSb Superlattices with Ultralow Bandgap.

Quasiparticles with Dirac-type dispersion can be observed in nearly gapless bulk semiconductors alloys in which the bandgap is controlled through the material composition. We demonstrate that the Dirac dispersion can be realized in short-period InAsSb/InAsSb metamorphic superlattices with the bandgap tuned to zero by adjusting the superlattice period and layer strain. The new material has anisotropic carrier dispersion: the carrier energy associated with the in-plane motion is proportional to the wave vector and characterized by the Fermi velocity v, and the dispersion corresponding to the motion in the growth direction is quadratic.

Particle correlations and evidence for dark state condensation in a cold dipolar exciton fluid.

Dipolar excitons are long-lived quasi-particle excitations in semiconductor heterostructure that carry an electric dipole. Cold dipolar excitons are expected to have new quantum and classical multi-particle correlation regimes, as well as several collective phases, resulting from the intricate interplay between the many-body interactions and their quantum nature. Here we show experimental evidence of a few correlation regimes of a cold dipolar exciton fluid, created optically in a semiconductor bilayer heterostructure.

Are excitons really bosons?

Non-bosonic commutation relations of exciton operators discovered by Keldysh and Kozlov (1968 Zh. Eksp. Teor.