29 - Charged Bosons in Quantum Heterostructures

Summary

Abstract

We show that heterostructures may give rise to charged bosons. Bosons may be formed as a result of two quantum-well holes pairing in a repulsive potential. In the case where at least one hole has a negative effective mass, the repulsive electrostatic interaction may be converted to an effective attraction. The effect is a general one, possible in quantum layers of most cubic semiconductors. We compute the x-dependent hole-hole binding energy for AlGaAs/In_xGa_1−xAs/GaAs quantum layers, taking account of the screening by a degenerate background gas of positive mass holes. We conclude that bound hole–hole pairs should be observable in infrared absorption experiments.

The possibility of creating a controlled gas of bosons has stimulated years of work on excitonic systems [1–4], spin-polarized hydrogen [5], and atom trapping [6]. But the only opportunity of charged boson formation in solids which is widely accepted is Cooper pairing. The possibility of any other mechanism of charged boson formation in solids is a very exciting topic for investigation. Needless to say, the superfluidity of a charged boson gas in solids would be manifested as superconductivity.

In this work we discuss regular electrostatic repulsion, which, in the case where at least one of the carriers has a negative effective mass, may be converted to an effective attraction, as a mechanism of pairing. A composite boson, carrying charge 2|e|, may be formed in such a case.

It is known that the presence of negative mass states of carriers is a general property of crystal band structure.