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Journal of Physics B: Atomic, Molecular and Optical Physics - latest papers
Latest articles for Journal of Physics B: Atomic, Molecular and Optical Physics
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Nano-processing of nanodiamond coated ultrathin glass, semiconductor and metalfoils with femtosecond pulses
Nanodiamonds are a key material for quantum science and technology applications. The capability to nano-structure the nanodiamond-coated substrates is highly desired for quantum science and technology applications. This study demonstrates femtosecond pulse-based nanoprocessing of nanodiamond functionalized ultrathin foldable glass, silicon wafers, and metal sheets using spherical objectives and cylindrical lens. We show that the fluorescence and microwave magnetic resonance of NV centers on ultrathin glass remain preserved for isolated intense femtosecond pulse exposure using spherical objectives, even when the substrates undergo surface structuring, cracks, or cutting. However, the nanodiamonds on ultrathin glass, silicon wafers and copper foils undergo further fragmentation for multiple pulse exposure in the laser line focus (with cylindrical lens) and lose their fluorescence when the surface is nano-structured. These results provide insights into how the femtosecond pulse illuminated nanodiamonds behave on diverse substrates. They might be useful for developing optical methods for fabricating quantum components and devices.
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Contributions of different quantum pathways to nonsequential double ionization by monochromatic and bichromatic laser fields
When nonsequential double ionization is treated using the strong-field approximation and the saddle-point (SP) method, the transition amplitude can be expressed as a coherent sum of the partial amplitudes corresponding to different SP solutions. For the case of the recollision excitation with subsequent ionization (RESI) mechanism of the nonsequential double ionization, we examine the partial contributions of the SP solutions which correspond to the electron responsible for the excitation. For a monochromatic linearly polarized laser field, we find that, in addition to the pair of the SP solutions with the shortest travel time, other SP solutions may also make a significant contribution to the photoelectron yield. Moreover, the SP solutions appear in pairs and exhibit notable modifications in comparison to those observed in high-order above-threshold ionization. Furthermore, for a bichromatic linearly polarized driving field, we investigate the intensity range obtained using the simpleman’s model for which the RESI mechanism is dominant. We find that this range must be modified if the photoelectron yield corresponding to the SP solution for which the photoelectron has the highest energy upon return to the parent ion is small. This is particularly the case for the excitation channels involving loosely bound excited states.
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The dynamics of Tonks–Girardeau gas excited by a pulse drive
In this paper we study the dynamics of Tonks–Girardeau (TG) gases in a harmonic potential driven by a Gaussian pulse, which is in correspondence with the excitation dynamics of electrons in matter driven by an ultrashort laser pulse. The evolving dynamics of the TG gas are obtained with a Bose–Fermi mapping method combined with numerical techniques. We calculate the evolving dynamics of the occupation distribution of single-particle energy levels, the density distribution and the momentum distribution of the system. It is shown that the system arrives at a dynamically stable state at the end of driving. In the high-frequency regime, TG gases return back to the ground state, while in the low-frequency regime the population inversion exhibits that all atoms occupy high levels.
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Photon-assisted tunneling resonantly controlling spin current of a spin–orbit-coupled atom in a toroidal trap
The periodic flashing potential has proven to be a powerful tool for investigating directed atomic currents. By applying the flashing ring-shaped potential to spin–orbit (SO) coupled, noninteracting Bose–Einstein condensate (BEC) systems, through photon-assisted tunneling (resonance) techniques, we demonstrate the generation of tunable alternating (AC) spin and atomic mass currents that can be precisely controlled in terms of direction and strength. The underlying mechanism behind this phenomenon is that the flashing potential supplies enough photons to induce Rabi oscillations and provides momentum transfer for spin and atomic transport. As the single-particle ground state of the unperturbed SO-coupled BEC depends on the Raman coupling strength, we demonstrate how to generate and control AC spin currents in the cases where the initial state resides in a single-well or double-well phase. In particular, we realize and explain the mechanism of generating a net AC spin current without mass current through single-photon resonance processes. It is shown that these interesting resonance phenomena can be analytically described only by the simple three-level model, which creates the possibility of transparent controls of spin dynamics.
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Orientation dependence of residual current in graphene by few-cycle linearly polarized light
The orientation dependence of residual current in graphene using linearly polarized light is theoretically investigated by numerically solving the time-dependent Schrödinger equation. We find that the residual current exhibits an unexplored small-period sinusoidal modulation in addition to a large-period sinusoidal modulation as a function of polarization angle. Via decomposing the residual current into two components, parallel and perpendicular to the laser polarization direction, we confirm that the large-period modulation comes from the parallel current component, while the small-period modulation is from the perpendicular component. These two current components are both influenced by the asymmetric population distribution as a consequence of the Landau–Zener–Stückelberg interference. The result here demonstrates a strong link between graphene symmetry and residual current and provides some insights into the development of light-field-driven petahertz information technology.