We use a path integral quantum Monte Carlo method to simulate excitons and biexcitons in core shell nanocrystals with Type-I, II and quasi-Type II band alignments. Quantum Monte Carlo techniques allow for all quantum correlations to be included when determining the thermal ground state, thus producing accurate predictions of biexciton binding. These subtle quantum correlations are found to cause the biexciton to be binding with Type-I carrier localization and strongly anti-binding with Type-II carrier localization, in agreement with experiment for both core shell nanocrystals and dot in rod nanocrystal structures. Simple treatments based on perturbative approaches are shown to miss this important transition in the biexciton binding. Understanding these correlations offers prospects to engineer strong biexciton anti-binding which is crucial to the design of nanocrystals for single exciton lasing applications.

No abstract

No abstract

We study the response of exciton complexes in semiconductor quantum rings to vertical electric fields, using path integral quantum Monte Carlo simulations. The interaction of a vertical applied field and the piezoelectric fields of the ring with strongly-correlated excitonic complexes switches excitons between two different lateral locations within the ring . This control should be observable through polarizability and dipole measurements, and, for biexcitons, an energy shift beyond the normal Stark shift.