共查询到20条相似文献,搜索用时 468 毫秒
1.
2.
Redshifts of luminescence relative to optical absorption bands (Stokes shifts) of molecules and of defects in solids are universally attributed to slow atomic relaxations on the grounds that electronic transitions are fast (Franck-Condon principle). Here we report a novel phenomenon that can occur only in the solid state: Stokes shifts caused by slow electronic relaxations. We demonstrate that the phenomenon occurs in the nonbridging oxygen defect in amorphous SiO2. We predict that another defect (OH group), which can exist in either crystalline or amorphous SiO2, has a similar Stokes shift, but it arises from a mix of lattice and electronic relaxations with manifest differences in the two phases. 相似文献
3.
Iwasawa H Douglas JF Sato K Masui T Yoshida Y Sun Z Eisaki H Bando H Ino A Arita M Shimada K Namatame H Taniguchi M Tajima S Uchida S Saitoh T Dessau DS Aiura Y 《Physical review letters》2008,101(15):157005
Angle-resolved photoemission spectroscopy with low-energy tunable photons along the nodal direction of oxygen isotope substituted Bi(2)Sr(2)CaCu(2)O(8+delta) reveals a distinct oxygen isotope shift near the electron-boson coupling "kink" in the electronic dispersion. The magnitude (a few meV) and direction of the kink shift are as expected due to the measured isotopic shift of phonon frequency, and are also in agreement with theoretical expectations. This demonstrates the participation of the phonons as dominant players, as well as pinpointing the most relevant of the phonon branches. 相似文献
4.
研究了非谐振势中超流Fermi气体的集体激发. 基于一维超流流体动力学模型, 采用变分法获得了体系从分子Bose-Einstein凝聚端渡越到Cooper对凝聚端时系统的两个低能激发模, 即偶极模和呼吸模. 分析发现: 在整个跨越区偶极模和呼吸模都发生了频移现象, 且在BCS端频移更加显著. 进一步研究发现在不同驱动振幅激发下超流Fermi气体质量中心和宽度变化呈现出了复杂动力学特性, 由于非谐振势的贡献,超流Fermi气体两低能模发生耦合, 使宽度变化产生量子拍频现象, 且拍频频率随着驱动振幅的增加而增大. 这种非线性耦合对外部驱动的响应在幺正区尤其显著.
关键词:
超流Fermi气体
非谐振势
集体激发 相似文献
5.
The spontaneous emission spectrum from two quantum dots (QDs) that are strongly coupled with a single-mode nanocavity is investigated using rigorous numerical calculations and simple analytical solutions of quantum dynamics. The emission spectra both from the side and along the axis of the cavity are considered. Modification of two parameters, the coupling strength and the detuning between the transition frequencies of the two quantum dots, allows us to efficiently control the shape of the spontaneous emission spectrum. Different profiles and their physical origins can be well understood in the dressed-state picture for the light-QD interaction in the on-resonance and off-resonance situations. In the on-resonance situation, the emission spectra exhibit symmetric features, and they are not altered by the asymmetry in the coupling pa- rameters. The axis spectra show two emission peaks while the side spectra have three emission peaks. In the off-resonance situation, the emission spectra always show an asymmetrical three-peak feature. When the two QDs have different decay parameters, singular features (a peak or a dip) can take place at the frequency of the cavity mode, and this is attributed to the unbalanced process of the emission and absorption of a single photon. 相似文献
6.
X. Caillet C. Simon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):341-348
We analyze the achievable precision for single-qubit gates that
are based on off-resonant Raman transitions between two
near-degenerate ground states via a virtually excited state. In
particular, we study the errors due to non-perfect adiabaticity
and due to spontaneous emission from the excited state. For the
case of non-adiabaticity, we calculate the error as a function of
the dimensionless parameter χ=Δτ, where Δ is
the detuning of the Raman beams and τ is the gate time. For
the case of spontaneous emission, we give an analytical argument
that the gate errors are approximately equal to Λ
γ/Δ, where Λ is the rotation angle of the
one-qubit gate and γ is the spontaneous decay rate, and we
show numerically that this estimate holds to good approximation. 相似文献
7.
Francesco Giacosa 《The European Physical Journal C - Particles and Fields》2010,65(3-4):449-455
A σ-model with two linked Mexican hats is discussed. This scenario could be realized in low-energy QCD when the ground state and the first excited (pseudo)scalar mesons are included, and where not only in the subspace of the ground states, but also in that of the first excited states, a Mexican hat potential is present. This possibility can change some basic features of a low-energy hadronic theory of QCD. It is also shown that spontaneous breaking of parity can occur in the vacuum for some parameter choice of the model. 相似文献
8.
9.
van Driel AF Allan G Delerue C Lodahl P Vos WL Vanmaekelbergh D 《Physical review letters》2005,95(23):236804
We studied the rate of spontaneous emission from colloidal CdSe and CdTe nanocrystals at room temperature. The decay rate, obtained from luminescence decay curves, increases with the emission frequency in a supralinear way. This dependence is explained by the thermal occupation of dark exciton states at room temperature, giving rise to a strong attenuation of the rate of emission. The supralinear dependence is in agreement with the results of tight-binding calculations. 相似文献
10.
A low-energy electron diffraction analysis of a {211} surface of body-centered cubic iron reveals relaxations in the directions perpendicular and parallel to the surface plane. Both relaxations alternate in successive layers. The perpendicular relaxation goes from contraction of 10.5% to expansion of 5% to contraction of 1%. The parallel relaxation goes from a shift of the first layer of 0.24Å (10% of the nearest neighbor distance) toward more symmetrical registration with the second layer, to an opposite shift of 0.035 Å of the second layer with respect to the third. 相似文献
11.
M. V. Fedorov M. A. Efremov V. P. Yakovlev W. P. Schleich 《Journal of Experimental and Theoretical Physics》2003,97(3):522-538
The scattering of atoms by a resonance standing light wave is considered under conditions when the lower of two resonance levels is metastable, while the upper level rapidly decays due to mainly spontaneous radiative transitions to the nonresonance levels of an atom. The diffraction scattering regime is studied, when the Rabi frequency is sufficiently high and many diffraction maxima are formed due to scattering. The dynamics of spontaneous radiation of an atom is investigated. It is shown that scattering slows down substantially the radiative decay of the atom. The regions and characteristics of the power and exponential decay are determined. The adiabatic and nonadiabatic scattering regimes are studied. It is shown that the wave packets of atoms in the metastable and resonance excited states narrow down during scattering. A limiting (minimal) size of the wave packets is found, which is achieved upon nonadiabatic scattering in the case of a sufficiently long interaction time. 相似文献
12.
First principles calculations of relationship between the Cu surface states and relaxations 下载免费PDF全文
In this paper the relationship between the surface relaxations and the electron
density distributions of surface states of Cu(100), Cu(110), and Cu(111)
surfaces is obtained by first-principles calculations. The calculations
indicate that relaxations mainly occur in the layers at which the surface
states electrons are localized, and the magnitudes of the multilayer
relaxations correspond to the difference of electron density of
surface states between adjacent layers. The larger the interlayer relaxation
is, the larger the difference of electron density of surface states between
two layers is. 相似文献
13.
14.
Kierein J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1990,18(1):61-63
The Compton effect interpretation of astrophysical red shifts not only provides the mechanism for intrinsic red shifts of quasi-stellar sources, the solar limb, and other objects, but also results in a new cosmological model. This static model of the Universe is consistent with the Einstein static universe, since there are no unbalanced processes introduced into the model that would cause it to either expand or contract. The amount of radiation being transformed into matter is equal to the amount of radiation being released by the destruction of matter. The observed red shift is explained without the presumption that objects are moving away from each other. Thus, all the reasons for changing to nonstatic models of the Universe are answered by this model 相似文献
15.
We investigate the entanglement between two atoms in an overdamped cavity injected with squeezed vacuum when these two atoms are initially prepared in coherent states. It is shown that the stationary entanglement exhibits a strong dependence on the initial state of the two atoms when the spontaneous emission rate of each atom is equal to the collective spontaneous emission rate, corresponding to the case where the two atoms are close together. It is found that the stationary entanglement of two atoms increases with decreasing effective atomic cooperativity parameter. The squeezed vacuum can enhance the entanglement of two atoms when the atoms are initially in coherent states. Valuably, this provides us with a feasible way to manipulate and control the entanglement, by changing the relative phases and the amplitudes of the polarized atoms and by varying the effective atomic cooperativity parameter of the system, even though the cavity is a bad one. When the spontaneous emission rate of each atom is not equal to the collective spontaneous emission rate, the steady-state entanglement of two atoms always maintains the same value, as the amplitudes of the polarized atoms varies. Moreover, the larger the degree of two-photon correlation, the stronger the steady-state entanglement between the atoms. 相似文献
16.
本文提出一个方案以通过探测光子的衰减来制备囚禁在一个腔中的若干个原子的W态。在我们的方案中,腔的衰减率远大于原子与腔的耦合强度。这样,对腔品质因子的要求被大大降低。这在实验上是很重要的。本方案的另一个优点是通过拉曼跃迁原子总是处于两个基态,因而原子的自发辐射也被抑制。 相似文献
17.
ZHAN Zhi-Ming 《理论物理通讯》2010,54(2):355-358
We propose a scheme to generate the W states with manySQUIDs (superconducting-quantum-interference-devices) in cavity QED viaRaman transition. In this scheme, the transfer of quantum informationbetween the SQUIDs and cavity is not required. And the cavity field is onlyvirtually excited, thus the cavity decay is suppressed during the W statesgeneration. The SQUIDs are always populated in the two ground states.Therefore, the scheme is insensitive to the spontaneous emission of theexcited level of the SQUID and cavity decay. 相似文献
18.
Envelope-induced pitch shifts were measured for exponentially decaying complex tones consisting of two sinusoidal components with frequencies f1 = nf0 + 50 Hz and f2 = (n + 1) f0 + 50 Hz, where n equals 3, 4, or 5 and exponential decay rates were 0, 0.5, 1, and 2 dB/ms. Four subjects adjusted a sinusoidal comparison tone to match the virtual pitch of the (missing) fundamental and the pitches of the lower and upper partials f1 and f2. Pitch shifts for f1 are generally less, and pitch shifts for f2 always greater, than envelope-induced shifts observed in isolated sinusoidal tones of comparable frequency and envelope decay rate. Pitch-shift functions for virtual pitch are similar in magnitude and shape to average pitch-shift functions of the partials, which supports the idea that virtual pitch depends on spectral pitch. 相似文献
19.
Effect of atomic initial phase difference on spontaneous emission of an atom embedded in photonic crystal 下载免费PDF全文
<正>We investigate the effect of initial phase difference between the two excited states of a V-type three-level atom on its steady state behaviour of spontaneous emission.A modified density of modes is introduced to calculate the spontaneous emission spectra in photonic crystal.Spectra in free space are also shown to compare with that in photonic crystal with different relative positions of the excited levels from upper band-edge frequency.It is found that the initial phase difference plays an important role in the quantum interference property between the two decay channels.For a zero initial phase,destructive property is presented in the spectra.With the increase of initial phase difference,quantum interference between the two decay channels from upper levels to ground level turns to be constructive.Furthermore, we give an interpretation for the property of these spectra. 相似文献
20.
Phase Control of Spontaneous Emission of a Three-Level Atom in Two Bichromatic Fields 总被引:1,自引:0,他引:1 下载免费PDF全文
We use the relative phase difference of two bichromatic fields of equal frequency differences for the coherent control of spontaneous emission of a three-level atom in the A configuration, diffects such as selective and total cancellation of fluorescence decay are obtained simply by varying the phase difference. The phese dependence of fluorescence spectra is attributed to the fact that the four different field components induce the transitions in a closed loop configuratiou. 相似文献