Cone-Shell Quantum Structures in Electric and Magnetic Fields as Switchable Traps for Photoexcited Charge Carriers

The optical emission of cone-shell quantum structures (CSQS) under vertical electric (F) and magnetic (B) fields is studied by means of simulations. A CSQS has a unique shape, where an electric field induces the transformation of the hole probability density from a disk into a quantum-ring with a tunable radius. The present study addresses the influence of an additional magnetic field. A common description for the influence of a B-field on charge carriers confined in a quantum dot is the Fock-Darwin model, which introduces the angular momentum quantum number l to describe the splitting of the energy levels. For a CSQS with the hole in the quantum ring state, the present simulations demonstrate a B-dependence of the hole energy which substantially deviates from the prediction of the Fock-Darwin model. In particular, the energy of exited states with a hole l(h)> 0 can become lower than the ground state energy with l(h)= 0. Because for the lowest-energy state the electron le is always zero, states with l(h)> 0 are optically dark due to selection rules. This allows switching from a bright state (l(h)= 0) to a dark state (l(h)> 0) or vice versa by changing the strength of the F or B field. This effect can be very interesting for trapping photoexcited charge carriers for a desired time. Furthermore, the influence of the CSQS shape on the fields required for the bright to dark state transition is investigated.

Automated summary

This study investigates the optical emission of cone-shell quantum structures (CSQS) under vertical electric and magnetic fields using simulations. The unique shape of CSQS undergoes a transformation from a disk into a quantum-ring with a tunable radius under an electric field. The influence of an additional magnetic field is also examined.