arXiv subjects

Petr Klenovsky

Publications and source records attributed to Petr Klenovsky.

4 recordsLinked to original sources

arXiv2025

Few-electron spin qubits in optically active GaAs quantum dots

The knowledge of the energy spectrum completely defines the dynamics of a quantum system for a given initial state. This makes spectroscopy a key characterization technique when studying or designing qubits and complex quantum systems. In semiconductor quantum dots, the electronic quantum states can be probed through charge transport spectroscopy, but the electric current itself disrupts the fragile quantum system, and the technique is practically limited to gate-defined quantum dots. Epitaxial quantum dots benefit from excellent optical properties, but are usually incompatible with charge transport, while alternative spectroscopy techniques provide only limited information. Here we demonstrate a spectroscopy technique which utilizes nuclear spins as a non-invasive probe. By using spin currents instead of the charge currents we achieve near-equilibrium probing. Experiments are conducted on low-strain GaAs/AlGaAs epitaxial dots, revealing energy spectra for charge configurations with up to seven electrons and the subtle properties of the multi-electron states. The rich variety of observations includes long-lived spin-qubit states in s and p shells, ground-state phase transitions, strong spin-orbit coupling regimes, and anomalously fast nuclear spin diffusion. Experiments are backed up by good agreement with the first-principles configuration-interaction numerical modelling. Our work uncovers few-electron states as a new operating regime for optically active quantum dots. Accurate control and probing of many-body states offers a test-bed system for fundamental physics studies, while prospective technological applications include electron spin qubits with extended coherence and scalable electrical control.

cond-mat.mes-hall↗

arXiv2025

Coulomb correlated multi-particle polarons

The electronic and emission properties of correlated multi-particle states are studied theoretically using ${\bf k}\cdot{\bf p}$ and the configuration interaction methods on a well-known and measured GaAs/AlGaAs quantum dots as a test system. The convergence of the calculated energies and radiative lifetimes of Coulomb correlated exciton, biexciton, positive and negative trions to experimentally observed values is reached when the electron-electron and hole-hole exchange interactions are neglected. That unexpected and striking result uncovers a rich structure of multi-particle states in the studied system, which is further quantitatively compared to published measurements in the literature, obtaining astonishingly good agreement. It is proposed that in real experiments the neglected electron-electron and hole-hole exchange interactions are emitted as acoustic phonons during the radiative recombination of the ground state of complexes, leading to the observation of polaronic multi-particle states. Analysis of their energy spectra provides a direct and measurable insight into the Coulomb correlation, being interesting both on the fundamental level and as possible experimentally tunable property in a wide variety of solid-state systems, in particular associated with quantum computing.

cond-mat.mes-hall↗

arXiv2023

Epitaxial growth and characterization of multi-layer site-controlled InGaAs quantum dots based on the buried stressor method

We report on the epitaxial growth, theoretical modeling, and structural as well as optical investigation of multi-layer, site-controlled quantum dots fabricated using the buried stressor method. This advanced growth technique utilizes the strain from a partially oxidized AlAs layer to induce site-selective nucleation of InGaAs quantum dots. By implementing strain-induced spectral nano-engineering, we achieve separation in emission energy by about 150 meV of positioned and non-positioned quantum dots and a local increase of the emitter density in a single layer. Furthermore, we achieve a threefold increase of the optical intensity and reduce the inhomogeneous broadening of the ensemble emission by 20% via stacking three layers of site-controlled emitters, which is particularly valuable for using the SCQDs in microlaser applications. Moreover, we obtain direct control over emission properties by adjusting the growth and fabrication parameters. Our optimization of site-controlled growth of quantum dots enables the development of photonic devices with enhanced light-matter interaction and microlasers with increased confinement factor and spontaneous emission coupling efficiency.

cond-mat.mes-hall↗

arXiv2022

GaAs quantum dots under quasi-uniaxial stress: experiment and theory

The optical properties of excitons confined in initially-unstrained GaAs/AlGaAs quantum dots are studied as a function of a variable quasi-uniaxial stress. To allow the validation of state-of-the-art computational tools for describing the optical properties of nanostructures, we determine the quantum dot morphology and the in-plane components of externally induced strain tensor at the quantum dot positions. Based on these \textsl{experimental} parameters, we calculate the strain-dependent excitonic emission energy, degree of linear polarization, and fine-structure splitting using a combination of eight-band ${\bf k}\cdot{\bf p}$ formalism with multiparticle corrections using the configuration interaction method. The experimental observations are quantitatively well reproduced by our calculations and deviations are discussed.

cond-mat.mes-hall↗