Coexistence of free excitonic matter with exciton magnetic polarons inCd1−xMnxTeunder nonresonant two-photon excitation

Abstract

Coexistence of free excitonic matter with exciton magnetic polarons (EMPs) in dilute magnetic semiconductors (DMSs) of ${\text{Cd}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{Te}$ for $0.04\ensuremath{\le}x\ensuremath{\le}0.36$ is demonstrated at superfluid He temperatures under nonresonant two-photon excitation. Unlike conventional one-photon excitation, both free excitons and biexcitons are observed employing this excitation method at $x=0.04$. Bose stimulation of biexcitons and a metal-insulator Mott transition are also observed under strong excitation. For $x\ensuremath{\ge}0.2$, only free excitons coexisting with EMPs are observed, which also exhibit stimulated emission under strong excitation. This implies that the Mn composition is an important kinematic parameter that affects the stability of biexcitons. Our results imply that a typical DMS system can exhibit strong optical phenomena, presumably correlated with various interesting magnetic effects, depending on excitation conditions.