Search results for "Principal quantum number"
showing 10 items of 31 documents
The influence of disorder on the exciton spectra in two-dimensional structures
2019
We study the role of disorder in the exciton spectra in two-dimensional (2D) semiconductors. These can be heterostructures, thin films and multilayers (so-called van der Waals structures) of organometallic perovskites, transition metal dichalcogenides and other semiconductors for optoelectronic applications. We model the disorder by introduction of a fractional Laplacian (with Le´vy index m, defining the degree of disorder) to the Scro¨dinger equation with 2D Coulomb potential. Combining analytical and numerical methods, we observe that the exciton exists only for m 4 1, while the point m = 1 (strongest disorder) corresponds to the exciton collapse. We show also that in the fractional (diso…
Spin-density waves in superdeformed quantum dots
1998
Abstract Electronic shell structure and spin effects in deformed quantum dots are investigated using spin-density functional theory. We recently suggested (Koskinen et al., Phys. Rev. Lett. 79 (1997) 1389) that for circular dots, depending on the density of the two-dimensional electron gas and the electron number, a spin-density wave-like state can occur as a possible ground state. Here these studies are extended to deformed and superdeformed dots, which approach the limit of a finite quantum wire.
Controlling the interactions of a few cold Rb Rydberg atoms by radiofrequency-assisted F\"orster resonances
2014
Long-range interactions between cold Rydberg atoms, which are used in many important applications, can be enhanced using F\"orster resonances between collective many-body states controlled by an external electric field. Here we report on the first experimental observation of highly-resolved radio-frequency-assisted F\"orster resonances in a few cold Rb Rydberg atoms. We also observed radio-frequency-induced F\"orster resonances which cannot be tuned by a dc electric field. They imply an efficient transition from van der Waals to resonant dipole-dipole interaction due to Floquet sidebands of Rydberg levels appearing in the rf-field. This method can be applied to enhance the interactions of a…
Rydberg Series Excitation of a Single Trapped Ca+40 Ion for Precision Measurements and Principal Quantum Number Scalings
2021
A complete set of spectroscopic data is indispensable when using Rydberg states of trapped ions for quantum information processing. We carried out Rydberg series spectroscopy for $n{S}_{1/2}$ states with $38\ensuremath{\le}n\ensuremath{\le}65$ and for $n{D}_{5/2}$ states with $37\ensuremath{\le}n\ensuremath{\le}50$ on a single trapped $^{40}{\mathrm{Ca}}^{+}$ ion. We determined the ionization energy of 2 870 575.582(15) GHz, 60 times more accurately as compared to the accepted value and contradicting it by 7.5 standard deviations. We confirm quantum defect values of ${\ensuremath{\delta}}_{{S}_{1/2}}=1.802\text{ }995(5)$ and ${\ensuremath{\delta}}_{{D}_{5/2}}=0.626\text{ }888(9)$ for $n{S}_…
A note on Δn ≠ 0 Stark transitions in hydrogenlike atoms
1992
In a gaseous helium or hydrogen target slow muons or antiprotons are captured into orbits with a high principal quantum number (n = 15 to 50) to form (μ− α)+ ions, (pα)+ ions, or (pp) atoms respectively. In the subsequent deexcitation process Stark mixing of the intermediary states plays an important role. The successful Mainz Cascade Model assumed Δn = 0 for the Stark transitions, although formally no such selection rule exists. This note examines the reasons why Δn ≠ 0 Stark transitions play only a negligible role in the deexcitation cascade.
PROTONIUM: The Mainz Cascade Model
1990
Recent experiments at LEAR have studied extensively the properties of antiprotonic hydrogen, often also called protonium.
Role of excitons in double Raman resonances in GaAs quantum wells
1996
Raman scattering by longitudinal-optical phonons has been measured in GaAs-AlAs multiple quantum wells at high magnetic fields. Doubly resonant scattering processes are observed at photon energies corresponding to magneto-excitons with different principal quantum numbers for the incoming and outgoing channels. The existence of these initially forbidden scattering processes, their resonance energies, and their relative intensities are correctly reproduced by our theoretical description. The model takes into account the excitonic nature of the intermediate states, as well as scattering processes involving a nonzero in-plane phonon wave vector, which is required to allow inter-Landau level sca…
Three-step resonant photoionization spectroscopy of Ni and Ge: ionization potential and odd-parity Rydberg levels
2007
In preparation of a laser ion source, we have investigated multi-step laser ionization via Rydberg and autoionizing states for atomic Ni and Ge using a mass separator with an ion beam energy of 20 keV. For both elements resonant three-step excitation schemes suitable for modern Ti:sapphire laser systems were developed. Rydberg series in the range of principal quantum numbers 20 n 80 were localized, assigned and quantum numbers were allocated to the individual resonances. Ionization potentials (IP) were extracted from fits of the individual series and quantum defects of individual levels were analysed for confirmation of series assignment. For Ni the ionization potential could be extracted w…
Unavoidable decoherence in semiconductor quantum dots
2005
Phonon-induced unavoidable decoherence of orbital degrees of freedom in quantum dots is studied and the relevant time scales are estimated. Dephasing of excitons due to acoustic phonons and, in a polar medium, to optical phonons, including anharmonic effects and enhancement of the effective Fr\"ohlich constant due to localization, is assessed for typical self-assembled quantum dots. Temporal inefficiency of Pauli blocking due to lattice inertia is predicted. For quantum dots placed in a diluted magnetic semiconductor medium a magnon-induced dephasing of a spin is also estimated in accordance with experimental results.
Adiabatic quantum search scheme with atoms in a cavity driven by lasers
2007
We propose an implementation of the quantum search algorithm of a marked item in an unsorted list of N items by adiabatic passage in a cavity-laser-atom system. We use an ensemble of N identical three-level atoms trapped in a single-mode cavity and driven by two lasers. In each atom, the same level represents a database entry. One of the atoms is marked by having an energy gap between its two ground states. Appropriate time delays between the two laser pulses allow one to populate the marked state starting from an initial entangled state within a decoherence-free adiabatic subspace. The time to achieve such a process is shown to exhibit the Grover speedup.