arXiv subjects

B. D. Gerardot

Publications and source records attributed to B. D. Gerardot.

25 records · Page 2Linked to original sources

arXiv2006

Manipulating exciton fine-structure in quantum dots with a lateral electric field

The fine structure of the neutral exciton in a single self assembled InGaAs quantum dot is investigated under the effect of a lateral electric field. Stark shifts up to 1.5 meV, an increase in linewidth, and a decrease in photoluminescence intensity were observed due to the electric field. We show that the lateral electric field strongly affects the exciton fine structure splitting due to active manipulation of the single particle wave-functions. Remarkably, the splitting can be tuned over large values and through zero.

cond-mat.mes-hall↗

arXiv2006

Entangled Photon Pairs from Semiconductor Quantum Dots

Tomographic analysis demonstrates that the polarization state of pairs of photons emitted from a biexciton decay cascade becomes entangled when spectral filtering is applied. The measured density matrix of the photon pair satisfies the Peres criterion for entanglement by more than 3 standard deviations of the experimental uncertainty and violates Bell's inequality. We show that the spectral filtering erases the ``which path'' information contained in the photons color and that the remanent information in the quantum dot degrees of freedom is negligible.

quant-ph↗

arXiv2005

Absorption and photoluminescence spectroscopy on a single self-assembled charge-tunable quantum dot

We have performed detailed photoluminescence (PL) and absorption spectroscopy on the same single self-assembled quantum dot in a charge-tunable device. The transition from neutral to charged exciton in the PL occurs at a more negative voltage than the corresponding transition in absorption. We have developed a model of the Coulomb blockade to account for this observation. At large negative bias, the absorption broadens as a result of electron and hole tunneling. We observe resonant features in this regime whenever the quantum dot hole level is resonant with two-dimensional hole states located at the capping layer-blocking barrier interface in our structure.

cond-mat.mes-hall↗

arXiv2005

Voltage-controlled electron-hole interaction in a single quantum dot

The ground state of neutral and negatively charged excitons confined to a single self-assembled InGaAs quantum dot is probed in a direct absorption experiment by high resolution laser spectroscopy. We show how the anisotropic electron-hole exchange interaction depends on the exciton charge and demonstrate how the interaction can be switched on and off with a small dc voltage. Furthermore, we report polarization sensitive analysis of the excitonic interband transition in a single quantum dot as a function of charge with and without magnetic field.

cond-mat.mes-hall↗

arXiv2005

Spin-selective optical absorption of singly charged excitons in a quantum dot

We investigate high resolution laser absorption spectroscopy of a single InGaAs/GaAs self-assembled quantum dot embedded in a field-effect structure. We show experimentally that the interband optical absorption to the lower Zeeman branch of the singly charged exciton is strongly inhibited due to spin (Pauli) blockade of the optical transition. At high magnetic fields the optical absorption to the upper Zeeman branch dominates the absorption spectrum. We find however that the spin blockade is not complete and a 10% leakage remains at high magnetic fields. Applying a gate voltage to empty the dot of its resident electron turns off the spin blockade. This effect is observed at 1.5 K and up to 9 Tesla.

cond-mat.mes-hall↗

arXiv2004

Voltage-Controlled Optics of a Quantum Dot

We show how the optical properties of a single semiconductor quantum dot can be controlled with a small dc voltage applied to a gate electrode. We find that the transmission spectrum of the neutral exciton exhibits two narrow lines with $\sim 2$ $μ$eV linewidth. The splitting into two linearly polarized components arises through an exchange interaction within the exciton. The exchange interaction can be turned off by choosing a gate voltage where the dot is occupied with an additional electron. Saturation spectroscopy demonstrates that the neutral exciton behaves as a two-level system. Our experiments show that the remaining problem for manipulating excitonic quantum states in this system is spectral fluctuation on a $μ$eV energy scale.

cond-mat.mes-hall↗

arXiv2001

Photoluminescence of a single InAs quantum dot molecule under applied electric field

We study the electronic coupling between two vertically stacked InAs quantum dots, which are embedded in the center of a n-i-n structure. We use a micro-photoluminescence setup to optically isolate a single quantum dot pair and measure the time-averaged photoluminescence under an applied vertical electric field. We find that field tunable coupling between excited states of the two quantum dots leads to charge transfer from one dot to the other. We model the spectra including simultaneously the field dependent charge transfer and exciton capture rates, and the many-body spectra of the quantum dot molecule for different carrier configurations.

cond-mat.str-el↗