1 research outputs found
Engineering Dirac Materials: Metamorphic InAs<sub>1β<i>x</i></sub>Sb<sub><i>x</i></sub>/InAs<sub>1β<i>y</i></sub>Sb<sub><i>y</i></sub> 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 InAs<sub>1β<i>x</i></sub>Sb<sub><i>x</i></sub>/InAs<sub>1β<i>y</i></sub>Sb<sub><i>y</i></sub> 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 <i>v</i><sub>F</sub>, and the dispersion corresponding to the motion
in the growth direction is quadratic. Experimental estimate of the
Fermi velocity gives <i>v</i><sub>F</sub> = 6.7 Γ 10<sup>5</sup> m/s. Remarkably, the Fermi velocity in this system can be
controlled by varying the overlap between electron and hole states
in the superlattice. Extreme design flexibility makes the short-period
metamorphic InAs<sub>1β<i>x</i></sub>Sb<sub><i>x</i></sub>/InAs<sub>1β<i>y</i></sub>Sb<sub><i>y</i></sub> superlattice a new prospective platform
for studying the effects of charge-carrier chirality and topologically
nontrivial states in structures with the inverted bandgaps