Abstract
Superfluidity has been predicted and now observed in a number of different electron-hole double-layer semiconductor heterostructures. In some of the heterostructures, such as GaAs and Ge-Si electron-hole double quantum wells, there is a strong mismatch between the electron and hole effective masses. We systematically investigate the sensitivity to unequal masses of the superfluid properties and the self-consistent screening of the electron-hole pairing interaction. We find that the superfluid properties are insensitive to mass imbalance in the low density BEC regime of strongly-coupled boson-like electron-hole pairs. At higher densities, in the BEC-BCS crossover regime of fermionic pairs, we find that mass imbalance between electrons and holes weakens the superfluidity and expands the density range for the BEC-BCS crossover regime. This permits screening to kill the superfluid at a lower density than for equal masses.
Highlights
Matter 2021, 6, 14. https://doi.org/Pairing of fermions with significantly different masses is currently of great theoretical and experimental interest in condensed matter and nuclear physics
We find that the sensitivity of the electron-hole superfluid properties to unequal masses is markedly different in the BEC regime and the BEC-BCS crossover regime
This is consistent with the picture in the BEC regime of tightly bound electron-hole pairs
Summary
Pairing of fermions with significantly different masses is currently of great theoretical and experimental interest in condensed matter and nuclear physics. In such systems, there is potential to generate novel superfluid phenomena including a complex structure of the vortex state, with the vortex-core density depleted in a very different manner for the light and the heavy fermion components [1]. There is the possibility of exotic superfluid phases across the BEC-BCS crossover. These include the Fulde-Ferrell-LarkinOvchinnikov [2] superfluid phase and the Sarma superfluid phase with two Fermi surfaces (breached pair phase) [3], and possibly a Larkin-Ovchinnikov supersolid phase [4]. The predicted transition temperatures for exotic phases are inaccessibly low [6], even if evaporative cooling techniques are exploited
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