"Life and coherence time of the dark exciton in semiconductor quantum dot."

TYPESolid State Institute Seminar
Speaker:Mr. Ido Schwartz
Affiliation:Dept. of Physics and Solid State Institute, Technion
Location:Solid State Auditorium(Entrance)
Remark:M.Sc. Student of Professor David Gershoni
Abstract:A dark exciton (DE) is an optically inactive electron-hole pair in semiconductors [1]. We report on an all optical novel method for measuring the spin state of the DE in semiconductor quantum dot. We do that by resonantly exciting a DE into a two-exciton state. The absorption is conditional upon the relative angle between the DE spin direction and the polarization of the exciting laser pulse. The magnitude of the absorption is then directly deduced from the intensity of the emission which results from the biexciton recombination back to the DE state. The method which is similar to the one that we developed for reading the state of the bright exciton [2], yields DE lifetimes of order 1μSec and comparably long coherence time. These measurements establish that the DE can be used as a viable matter spin qubit. [1 ] E.Poem, Y.Kodriano, C. Tradonsky, N.H. Lindner, B. D. Gerardot, P. M. Petroff and D. Gershoni " Accessing the dark exciton with light " Nature Physics 6, 993-997, (2010) [2 ] Y. Benny, S. Khatsevich, Y. Kodriano, E. Poem, R. Presman, D. Galushko, P.M. Petroff and D. Gershoni " Coherent Optical Writing and Reading of the Exciton Spin State in Single Quantum Dots " Phys. Rev. Lett. 106, 040504, (2011). [3 ] E. Poem, O. Kenneth, Y. Kodriano, Y. Benny, S. Khatsevich, J. E. Avron, D. Gershoni " Optically induced rotation of a quantum dot exciton spin " Phys. Rev. Lett. 107, 087401, (2011).