Progress in the Bose-Einstein condensation of biexcitons in CuCl

Abstract
The occupancy of the K=0 ground state of the biexciton in CuCl is measured by nonlinear optical methods. An increase of the optical phase conjugation signal is observed when a random high density of biexcitons is injected into the crystal. The corresponding increase of coherency is attributed to a quantum attraction towards a Bose-Einstein condensate of biexcitons.