Flexible manipulation of quantum dots by single-pulse optical vortices*

Optical vortices (OV) are light fields with surprising properties, such as orbital angular momentum (AM), strong longitudinal components, and more, that can be exploited to control matter in new ways. Here we show that a single-pulse of an OV with the right parameters --degree of focusing, polarization, orbital AM, etc-- can precisely manipulate the electronic state of semiconductor quantum dots (QD) [1, 2]. Our models demonstrate the possibility of creating: i) heavy-hole excitons with arbitrary orbital AM, and ii) light-hole excitons with zero band+spin AM, with or without orbital AM. Such states can be named "envelope-forbidden" (i) or "spin-forbidden" (ii), since they cannot be excited by Gaussian light beams. In addition, we present potential applications to quantum technology: spin-forbidden states allow sub-picosecond spin flips of an extra electron charging the QD or the encoding of information on dark excitons, while envelope-forbidden states allow for the generation of currents that can produce magnetic fields at the nanoscale.

[1] Quinteiro, G.F. and Tamborenea, P.I., 2009. Physical Review B, 79(15), p.155450.
[2] Quinteiro, G.F. and Kuhn, T., 2014. Physical Review B, 90(11), p.115401.