Browsing by Author "Ramachandhran, B."

Now showing 1 - 3 of 3
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    Cavity-assisted dynamical spin-orbit coupling in cold atoms
    (American Physical Society, 2014) Dong, Lin; Zhou, Lu; Wu, Biao; Ramachandhran, B.; Pu, Han; Rice Quantum Institute
    We consider ultracold atoms subjected to a cavity-assisted two-photon Raman transition. The Raman coupling gives rise to effective spin-orbit interaction which couples the atom's center-of-mass motion to its pseudospin degrees of freedom. Meanwhile, the cavity photon field is dynamically affected by the atom. This feedback between the atom and photons leads to a dramatic modification of the atomic dispersion relation, and further leads to dynamical instability of the system. We propose to detect the change in the cavity photon number as a direct way to demonstrate dynamical instability.
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    Controlling Condensate Collapse and Expansion with an Optical Feshbach Resonance
    (American Physical Society, 2013) Yan, Mi; DeSalvo, B.J.; Ramachandhran, B.; Pu, H.; Killian, T.C.
    We demonstrate control of the collapse and expansion of an Sr88 Bose-Einstein condensate using an optical Feshbach resonance near the S01−P13 intercombination transition at 689 nm. Significant changes in dynamics are caused by modifications of scattering length by up to ±10abg, where the background scattering length of Sr88 is abg=−2a0 (1a0=0.053  nm). Changes in scattering length are monitored through changes in the size of the condensate after a time-of-flight measurement. Because the background scattering length is close to zero, blue detuning of the optical Feshbach resonance laser with respect to a photoassociative resonance leads to increased interaction energy and a faster condensate expansion, whereas red detuning triggers a collapse of the condensate. The results are modeled with the time-dependent nonlinear Gross-Pitaevskii equation.
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    Emergence of topological and strongly correlated ground states in trapped Rashba spin-orbit-coupled Bose gases
    (American Physical Society, 2013) Ramachandhran, B.; Hu, Hui; Pu, Han
    We theoretically study an interacting few-body system of Rashba spin-orbit-coupled two-component Bose gases confined in a harmonic trapping potential. We solve the interacting Hamiltonian at large Rashba coupling strengths using an exact-diagonalization scheme, and obtain the ground-state phase diagram for a range of interatomic interactions and particle numbers. At small particle numbers, we observe that the bosons condense to an array of topological states with n+1/2 quantum angular momentum vortex configurations, where n=0,1,2,3,.... At large particle numbers, we observe two distinct regimes: at weaker-interaction strengths, we obtain ground states with topological and symmetry properties that are consistent with mean-field theory computations; at stronger-interaction strengths, we report the emergence of strongly correlated ground states.