A5064211669- Quantum and electron transport phenomena
- Semiconductor Quantum Structures and Devices
- Magnetic properties of thin films
- Quantum Dots Synthesis And Properties
- Quantum optics and atomic interactions
- Quantum Information and Cryptography
- Advancements in Semiconductor Devices and Circuit Design
- 2D Materials and Applications
- Semiconductor materials and devices
- Quantum Computing Algorithms and Architecture
- Chalcogenide Semiconductor Thin Films
- Semiconductor Lasers and Optical Devices
- Perovskite Materials and Applications
- Gyrotron and Vacuum Electronics Research
- Quantum many-body systems
- Physics of Superconductivity and Magnetism
- Nanowire Synthesis and Applications
- MXene and MAX Phase Materials
- Spectroscopy and Quantum Chemical Studies
- Advanced Energy Technologies and Civil Engineering Innovations
- Advanced Thermoelectric Materials and Devices
- Magnetic Properties of Alloys
- Phase-change materials and chalcogenides
- High-pressure geophysics and materials
- Solid-state spectroscopy and crystallography
University of Sheffield
2015-2024
University of Sussex
2024
Johannes Kepler University of Linz
2023
Osipyan Institute of Solid State Physics RAS
2007-2011
Russian Academy of Sciences
2007
Two-dimensional (2D) compounds provide unique building blocks for novel layered devices and hybrid photonic structures. However, large surface-to-volume ratio in thin films enhances the significance of surface interactions charging effects requiring new understanding. Here we use micro-photoluminescence (PL) ultrasonic force microscopy to explore influence dielectric environment on optical properties a few monolayer MoS2 films. PL spectra deposited SiO2 substrates are found vary widely. This...
Integration of quasi-two-dimensional (2D) films metal–chalcogenides in optical microcavities permits new photonic applications these materials. Here we present tunable with monolayer MoS2 or few GaSe films. We observe significant modification spectral and temporal properties photoluminescence (PL): PL is emitted spectrally narrow wavelength-tunable cavity modes quality factors up to 7400; a 10-fold lifetime shortening achieved, consequence Purcell enhancement the spontaneous emission rate.
Gallium chalcogenides are promising building blocks for novel van der Waals heterostructures. We report on the low-temperature micro-photoluminescence (PL) of GaTe and GaSe films with thicknesses ranging from 200 nm to a single unit cell. In both materials, PL shows dramatic decrease by 104–105 when film thickness is reduced 10 nm. Based evidence continuous-wave (cw) time-resolved PL, we propose model explaining as result non-radiative carrier escape via surface states. Our results emphasize...
We use photoluminescence spectroscopy of ''bright'' and ''dark'' exciton states in single InP/GaInP quantum dots to measure hyperfine interaction the valence band hole with nuclear spins polarized along sample growth axis. The ratio constants for (C) electron (A) is found be C/A~-0.11. In InP contribution spin 1/2 phosphorus nuclei hole-nuclear weak, which enables us determine experimentally value C 9/2 indium as C_In~-5 micro-eV. This high good agreement recent theoretical predictions...
Interaction with nuclear spins leads to decoherence and information loss in solid-state electron-spin qubits. One particular, ineradicable source of electron arises from the spin bath, driven by nuclear-nuclear dipolar interactions. Owing its many-body nature is difficult predict, especially for an important class strained nanostructures where quadrupolar effects have a significant but largely unknown impact. Here, we report direct measurement bath coherence individual self-assembled...
We demonstrate that efficient optical pumping of nuclear spins in semiconductor quantum dots (QDs) can be achieved by resonant optically forbidden transitions. This process corresponds to one-to-one conversion a photon absorbed the dot into polarized spin, and also has potential for initialization hole spin QDs. find employing this spin-forbidden process, polarization 65% achieved, markedly higher than from allowed transition, which saturates due low probability electron-nuclear flip-flop.
States with long coherence are a crucial requirement for qubits and quantum memories. Nuclear spins in epitaxial dots great candidate, offering excellent isolation from external environments on-demand coupling to optical flying qubits. However, times limited $\lesssim1$ ms by the dipole-dipole interactions between nuclei their quadrupolar inhomogeneous crystal strain. Here, we combine strain engineering of nuclear spin ensemble tailored dynamical decoupling sequences achieve exceeding 100...
Non-classical light sources offer a myriad of possibilities in both fundamental science and commercial applications. Single photons are the most robust carriers quantum information can be exploited for linear optics processing. Scale-up requires miniaturisation waveguide circuit multiple single photon sources. Silicon photonics, driven by incentive optical interconnects is highly promising platform passive components, but integrated limited silicon's indirect band-gap. III–V semiconductor...
Abstract Combining external control with long spin lifetime and coherence is a key challenge for solid state qubits. Tunnel coupling electron Fermi reservoir provides robust charge in semiconductor quantum dots, but results undesired relaxation of nuclear spins through mechanisms that lack complete understanding. Here, we unravel the contributions tunnelling-assisted phonon-assisted by systematically adjusting tunnelling wide range, including limit an isolated dot. These experiments reveal...
The spin diffusion concept provides a classical description of purely quantum-mechanical evolution in inhomogeneously polarized many-body systems such as nuclear lattices. central localized electron alters way that is still poorly understood. Here, single GaAs/AlGaAs quantum dot witnessed the most direct manner from oscillatory relaxation dynamics. Electron found to accelerate relaxation, which we conclude long-discussed Knight-field-gradient barrier does not apply GaAs epitaxial dots. Our...
We demonstrate control by applied electric field of the charge states in single self-assembled InP quantum dots placed GaInP Schottky structures grown metalorganic vapor phase epitaxy. This has been enabled growth optimization leading to suppression formation large uncontrollably accumulating charge. Using bias- and polarization-dependent micro-photoluminescence, we identify exciton multi-particle carry out a systematic study neutral state dipole moment polarizability. analysis allows for...
We realize growth of self-catalyzed core-shell GaAs/GaAsP nanowires (NWs) on Si substrates using molecular-beam epitaxy. Transmission electron microscopy (TEM) single NWs confirms their high crystal quality and shows domination the zinc-blende phase. This is further confirmed in optics NWs, studied cw time-resolved photoluminescence (PL). A detailed comparison with uncapped GaAs emphasizes effect GaAsP capping suppressing non-radiative surface states: significant PL enhancement structures...
A wealth of atomistic information is contained within a self-assembled quantum dot (QD), associated with its chemical composition and the growth history. In presence quadrupolar nuclei, as in InGaAs QDs, much this inherited to nuclear spins via coupling between strain polar lattice electric quadrupole moments nuclei. Here, we present computational study recently introduced inverse spectra magnetic resonance technique assess suitability for extracting such structural information. We observe...
GaAs/AlGaAs quantum dots grown by in situ droplet etching and nanohole in-filling offer a combination of strong charge confinement, optical efficiency, high spatial symmetry advantageous for polarization entanglement spin-photon interface. Here, we study experimentally electron nuclear spin properties such dots. We find nearly vanishing $g$ factors $({g}_{e}<0.05)$, providing potential route electrically driven control schemes. Optical manipulation the environment is demonstrated with up to...
Abstract There is a growing interest in hybrid solid-state quantum systems where nuclear spins, interfaced to the electron spin qubit, are used as memory or qubit register. These approaches require long coherence, which until now seemed impossible owing disruptive effect of spin. Here we study InGaAs semiconductor dots, demonstrating millisecond-long collective coherence even under inhomogeneous coupling central We show that underlying decoherence mechanism spectral diffusion induced by...
The nature of the nano-scale environment presents a major challenge for solid-state implementation spin-based qubits. In this work, single electron spin in an optically pumped nanometer-sized III-V semiconductor quantum dot is used to control macroscopic nuclear several thousand nuclei, freezing its decay and leading life-times exceeding 100 seconds at low temperatures. Few-millisecond-fast optical initialization followed by slow exhibiting random telegraph signals long delay times, arising...
Nuclear spin polarization dynamics are measured in optically pumped individual $\text{GaAs}/{\text{Al}}_{x}{\text{Ga}}_{1\ensuremath{-}x}\text{As}$ interface quantum dots by detecting the time dependence of Overhauser shift photoluminescence spectra. Long nuclear decay times $\ensuremath{\approx}1\text{ }\text{min}$ have been found indicating inefficient diffusion from GaAs dot into surrounding AlGaAs matrix externally applied magnetic field. A spin-diffusion coefficient two orders lower...