cuprous-oxide; low-temperature; decay; paraexcitons; molecules;thermodynamics; statistics; scattering; kinetics; silicon
Excitons in high-purity crystals of Cu2O undergo a density-dependent lifetime that opposes Bose-Einstein condensation (BEC). This rapid decay rate of excitons at a density n has generally been attributed to Auger recombination having the form dn/dt = -An(2), where A is an exciton-Auger constant. Various measurements of A, however, have reported values that are orders-of-magnitude larger than the existing theory. In response to this conundrum, recent work has suggested that excitons bind into excitonic molecules, or biexcitons, which are short-lived and expected to be optically inactive. Of particular interest is the case of excitons confined to a parabolic strain well-a method that has recently achieved exciton densities approaching BEC. In this paper we report time-and space-resolved luminescence data that supports the existence of short-lived biexcitons in a strain well, implying an exciton loss rate of the form dn/dt = -2 Cn(2) with a biexciton capture coefficient C(T) proportional to 1/T, as predicted by basic thermodynamics. This alternate theory will be considered in relation to recent experiments on the subject.
Wolfe, J. P., & Jang, J. I. (2014). The search for Bose–Einstein condensation of excitons in Cu2O: exciton-Auger recombination versus biexciton formation. New Journal of Physics, 16(12), 123048.
Wolfe, James P. and Jang, Joon I., "The search for Bose-Einstein condensation of excitons in Cu2O: exciton-Auger recombination versus biexciton formation" (2014). Physics, Applied Physics and Astronomy Faculty Scholarship. 4.