Upcoming Colloquia

Auger Recombination and Nanocrystal Lasing

Victor Klimov

Softmatter Nanotechnology and Advanced Spectroscopy,
Chemistry Division
Los Alamos National Laboratory,
Los Alamos, New Mexico 87545, USA

Monday, March 29, 10am

Chemistry Division Auditorium, TA-46, Bld. 535, Rm. 103


Using semiconductor nanocrystals (NCs), one can produce extremely strong spatial confinement of electronic wave functions not accessible with other types of nanostructures. One consequence of this effect is a significant enhancement in carrier-carrier interactions that leads to a number of novel physical phenomena, including ultrafast multiexciton decay due to Auger recombination. Auger recombination is a process in which the electron-hole recombination energy is not emitted as a photon but is transferred to a third carrier. In bulk semiconductors, Auger recombination is inhibited by kinematic restrictions imposed by energy and translational-momentum conservation that lead to the development of a thermal activation threshold for this process. However, because of relaxation of momentum conservation, the activation threshold is removed in NCs, which leads to a significant enhancement in the efficiency of Auger recombination. One consequence of fast Auger decay is very short lifetimes of optical gain in NCs that greatly complicate the applications of these nanostructures in practical lasing technologies. In this lecture, I will start with fundamentals of both Auger recombination and optical gain in strongly confined systems, and then talk on the most recent approaches to suppression of Auger decay using various types of engineered heteronanostructures. I will also describe a novel concept for NC lasing using single-exciton optical gain enabled by giant exciton-exciton repulsion in type-II hetero-NCs that produce efficient spatial separation of electrons and holes.