Photon Trajectories in Incoherent Atomic Radiation Trapping as Lévy Flights

Nunes-Pereira, Eduardo J.; Martinho, J. M. G.; Berberan‐Santos, Mário N.

doi:10.1103/physrevlett.93.120201

Cited by 47 publications

(66 citation statements)

References 23 publications

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“…The cases of CFR Doppler and Lorentz resonance line radiation transfer give analytical ODF expressions and were considered in previous works [15,19]. For the Doppler case, one has µ ≃ 1 and thus Eq.…”

Section: Asymptotic Behavior Of the Jump Distributionmentioning

confidence: 99%

“…one can see that the slower the decrease in the ODF for smaller opacity values, the more important the higher jump sizes. For Doppler, Lorentz (and Voigt) CFR trapping, the ODF variation for small k values is either increasing or so slowly decreasing as to render even the first moment of the jump size distribution infinite [15,19]. The CFR Voigt case is a self-affine multifractal with two different characteristic Lévy flight µ's parameters, a µ ≃ 1 corresponding to the Doppler-like core radiation and a µ = 1/2 for Lorentz-like wing photons.…”

Section: Superdiffusive Behavior For Resonance Line Trappingmentioning

confidence: 99%

“…Therefore, the topology of the excitation random trajectory has to be related with the frequency redistribution of the emitted photons, since the jump length Probability Distribution Function (PDF) must consider all possible optical emission frequencies. This can be done as [19] …”

Section: Partial Frequency Redistributionmentioning

confidence: 99%

“…For the absorption spectrum, if the line shape function can be given by a power-law asymptotic in the wings [15,19], then one has…”

Section: Asymptotic Behavior Of the Jump Distributionmentioning

confidence: 99%

“…This is usually known as the Holstein-Biberman equation, named after seminal contributions in the 1940s [16,17,18]. It was shown, first using ad hoc arguments [19] and later demonstrated, that the motion of photons is superdiffusive.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Photonic superdiffusive motion in resonance line radiation trapping Partial frequency redistribution effects

Alves-Pereira

Nunes-Pereira

Martinho

et al. 2007

The Journal of Chemical Physics

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Section: Asymptotic Behavior Of the Jump Distributionmentioning

confidence: 99%

Section: Superdiffusive Behavior For Resonance Line Trappingmentioning

confidence: 99%

Section: Partial Frequency Redistributionmentioning

confidence: 99%

“…For the absorption spectrum, if the line shape function can be given by a power-law asymptotic in the wings [15,19], then one has…”

Section: Asymptotic Behavior Of the Jump Distributionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Photonic superdiffusive motion in resonance line radiation trapping Partial frequency redistribution effects

Alves-Pereira

Nunes-Pereira

Martinho

et al. 2007

The Journal of Chemical Physics

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Nanoscale Compositional Modification in Co/Pd Multilayers for Controllable Domain Wall Pinning in Racetrack Memory

Jin

Kumar

Gan

et al. 2018

Physica Rapid Research Ltrs

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In the era of social media, storage of information plays an important role. Magnetic domain wall memory devices are promising alternatives to hard disk drives for high-capacity storage. One of the challenges in making these devices for practical application is a precise control of domain wall displacement in nanowires. Researchers have extensively studied domain wall pinning based on topographical notches fabricated by lithography. However, scaling the domain wall memory to nanoscale requires better domain wall pinning strategies. In this letter, we demonstrate that the localized modification of magnetic properties in Co/Pd multilayer-based nanowires by ion implantation is an effective non-topographical approach to pin domain walls. First, by micromagnetic simulations, it is shown that the areas, where the composition is modified to tune the anisotropy and magnetization, act as domain wall pinning centers. Experimentally, from magnetization measurements and X-ray diffraction measurements at the thin film level, it is shown that the ion-implantation is effective in changing magnetic anisotropy. Devices have also been fabricated and, using Kerr images at different applied fields, it is shown that the domain walls are pinned at the B þ ion-implanted regions. These results demonstrate that localized compositional modification using ion-implantation can pin domain walls precisely. The achieved results are useful toward realizing high-capacity information storage.Domain wall (DW)-based devices such as racetrack memory have been proposed as promising candidates for high capacity, non-volatile information storage to replace hard disk drives. [1,2] In DW memory (DWM) with a perpendicular magnetic anisotropy (PMA), the domains with magnetization pointing up represent "1" and the regions with magnetization pointing down represent "0." [2,3] In order to read and write information, the DWs are moved by an electrical current which causes motion by the spin-transfer torque (STT) mechanism. [4][5][6][7] Spin Hall effect in heavy metal/ferromagnetic/insulator structures is another mechanism in which a torque is exerted by pure spin current. [8,9] In comparison to STT driving DW motion, pure spin-polarized current gives a high speed performance of DW devices. [10,11] The speed of DW motion in certain designs could reach km s À1 . [11] In order to increase the capacity of DWM, researchers proposed fabricating U-shape vertical nanowire to store data, like the trees planted in the forest. However, fabrication of such devices is challenging particularly for commercial purposes. The other structure is horizontal stripe shape, which suffers from the data storing overflowing issues because the two ends of nanowire cannot be connected. Zhang et al. [12] proposed a ring structure with DW ratchets, which could be utilized for addressing the data overflow issue without any additional overhead.For DW-based devices, the propagation of DWs show a stochastic behavior. This stochastic manner was a significant challenge for magnetic recording comm...

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Radiation trapping in a cold atomic gas

Labeyrie¹,

Kaiser²,

Delande

2005

Appl. Phys. B

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We experimentally study radiation trapping of near-resonant light in a cloud of laser-cooled rubidium atoms. Unlike in most previous studies, dealing with hot vapors, collisional broadening is here negligible and Doppler broadening due to the residual atomic velocity is narrower than the homogeneous broadening. This is an interesting new regime, at the boundary between coherent and incoherent radiation transport. We analyze in detail our low-temperature data (quasi-elastic regime) and then provide some experimental evidence for Doppler-based frequency redistribution. The data are compared with an analytical model valid for coherent transport and a Monte Carlo simulation including the Doppler effect

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Photon Trajectories in Incoherent Atomic Radiation Trapping as Lévy Flights

Cited by 47 publications

References 23 publications

Photonic superdiffusive motion in resonance line radiation trapping Partial frequency redistribution effects

Photonic superdiffusive motion in resonance line radiation trapping Partial frequency redistribution effects

Nanoscale Compositional Modification in Co/Pd Multilayers for Controllable Domain Wall Pinning in Racetrack Memory

Radiation trapping in a cold atomic gas

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