Damped Bloch oscillations of cold atoms in optical lattices

Abstract

The paper studies Bloch oscillations of cold neutral atoms in the optical lattice. The effect of spontaneous emission on the dynamics of the system is analyzed both analytically and numerically. The spontaneous emission is shown to cause (i) the decay of Bloch oscillations with the decrement given by the rate of spontaneous emission and (ii) the diffusive spreading of the atoms with a diffusion coefficient depending on both the rate of spontaneous emission and the Bloch frequency.

Delocalization-enhanced Bloch oscillations and driven resonant tunneling in optical lattices for precision force measurements

“…In fact, for shallow traps (U 0 E R ), collisions can result in the transition of the atom from the lowest band into the upper bands, which are only weakly bounded. This means that only collisions with small exchanges of momentum can effectively contribute to the broadening of k and hence γ exp < γ [44]. The lattice-recoil effect plays a smaller role since it excites the atoms into the second band (the energy gap between the first and the second band is typically E G ∼ E R ) and thus does not contribute to the BO signal.…”

“…The decay of the offdiagonal elements of the density matrix causes a sequential tunneling, which asymptotically gives incoherent diffusion σ 2 (t) ≈ Dt, with D as the diffusion constant [44]. The sequential tunneling processes have the effect of broadening the resonance spectrum.…”

“…Basic decoherence mechanisms are spontaneous emission, atom-atom interactions [43], random recoils by lattice photons [44], and environmental scattering (i.e., offresonance scattering by incoherent light or background gas collisions).…”

New Bloch Period for Interacting Cold Atoms in 1D Optical Lattices

“…In turn, these fundamentally new experiments have stimulated considerable progress in theory (see review [7], and references therein), and it can be safely stated that BO in diluted quasi one-dimensional gases is well understood today. Other directions of research focus on BO in the presence of relaxation processes (spontaneous emission) [8], BO in 2D optical lattices [9], and BO in the presence of atom-atom interactions ('BEC-regime') [10,11,12,13]. The present Letter deals with the third problem, which is approached here by an 'ab initio' analysis of the dynamics of a system of many atoms.…”

Sistemas não-lineares aplicados a condensados atômicos com interações dependentes do tempo.

“…a coerência do sistema é destruída antes dos elétrons completarem um ciclo de Bloch. Por isso é de grande interesse procurar outros sistemas, em que o período de Bloch, que é inversamente proporcional à magnitude da força constante e do período da rede, seja menor do que o tempo de relaxação [28]. Um desses sistemas é o condensado de Bose-Einstein, onde as oscilações de Bloch aparecem como oscilações de pacotes de onda de matéria em uma rede periódica, que possuem como vantagem a possibilidade do controle experimental sobre os parâmetros do potencial periódico e do condensado, tornando possível alcançar regimes inacessíveis a outros sistemas [5].…”