Polarized Fine Structure in the Photoluminescence Excitation Spectrum of a Negatively Charged Quantum Dot

Abstract

We report polarized photoluminescence excitation spectroscopy of the negative trion in single charge tunable InAs/GaAs quantum dots. The spectrum exhibits a p-shell resonance with polarized fine structure arising from the direct excitation of the electron spin triplet states. The energy splitting arises from the axially symmetric electron-hole exchange interaction. The magnitude and sign of the polarization are understood from the spin character of the triplet states and a small amount of quantum dot asymmetry, which mixes the wavefunctions through asymmetric e-e and e-h exchange interactions.

Coherent population trapping of an electron spin in a single negatively charged quantum dot

“…The sample under study contains self-assembled InAs QDs embedded in a Schottky diode structure, which gives us the ability to control the charging state of the QD [15,17]. In the experiment, we set the voltage such that only one electron is trapped inside the QD.…”

Accurate defect levels obtained from the HSE06 range-separated hybrid functional

“…7 Until now, however, studies of the FSS of neutral and charged exciton complexes have been limited to QDs of C 2v or lower symmetry. [2][3][4][5][6][7][8][9][10][11] In this Rapid Communication, we experimentally and theoretically investigate the FSS in QDs with high symmetry. Zincblende QDs of C 3v symmetry can ideally be achieved by choosing ͓111͔ as the crystallographic direction of crystal growth instead of the conventional ͓001͔ direction.…”

Origin of two-hole triplet splitting in circular quantum dots

“…[23] Negatively charged hot trions have been proposed for optically controlled spin devices. [1,2,3] These applications are supported by the high spin purity of electrons in QDs, which gives rise to strict spin selection rules and long spin lifetimes. [24] The suitability of positively charged trions is not clear a priori, as the valence band spin-orbit interaction can lead to significant hole spin mixing.…”

“…Yet, this resonance may be difficult to observe experimentally because T 0 tends to thermalize quickly to the singlet ground state. [1,3] The use of electrical charging control may facilitate this task. [4] Electron-hole exchange, which has been disregarded here for simplicity, will further split trion states with hole configurations T ± , and T * ± into dark and bright states.…”

“…[1,2,3] These applications rely on the fine structure of the triplet sublevels, which are split by tens of µeV even at zero magnetic field due to the electron-hole exchange interaction, each set of sublevels having a distinct response to circularly polarized light. [1,4] The same fine structure was expected for positive trions, [5] but recent optical measurements reveal the presence of an additional number of resonances and large (∼ meV) splittings, which cannot be accounted for by the weak electron-hole exchange interaction alone.…”