Bogoliubov Excitations of Inhomogeneous Bose-Einstein Condensates

Yali Gao, Yongyong Cai

Erez Gershnabel, Nadav Y. Katz, Roee Ozeri +3 more

We propose and demonstrate an echo method to reduce the inhomogeneous linewidth of Bogoliubov excitations, in a harmonically-trapped Bose-Einstein condensate. Our proposal includes the transfer of excitations with momentum $+q$ to $\ensuremath{-}q$ using a double two photon Bragg process, in which a substantial reduction of the inhomogeneous broadening is calculated. Furthermore, we predict an enhancement in the method's efficiency for low momentum due to many-body effects. As a proof of principle, the echo can also be implemented by using a four photon process, as is demonstrated experimentally.

Phan Thành Nam

Yasunari Kurita, Michikazu Kobayashi, Takao Morinari +2 more

We construct quantum field theory in an analog curved spacetime in Bose-Einstein condensates based on the Bogoliubov--de Gennes equations by exactly relating quantum particles in curved spacetime with Bogoliubov quasiparticle excitations in Bose-Einstein condensates. Here, we derive a simple formula relating the two, which can be used to calculate the particle creation spectrum by solving the time-dependent Bogoliubov--de Gennes equations. Using our formulation, we numerically investigate particle creation in an analog expanding universe which can be expressed as Bogoliubov quasiparticles in an expanding Bose-Einstein condensate. We obtain its spectrum, which follows the thermal Maxwell-Boltzmann distribution, the temperature of which is experimentally attainable. Our derivation of the analogy is useful for general Bose-Einstein condensates and not limited to homogeneous ones, and our simulation is an example of particle creations by solving the Bogoliubov--de Gennes equation in an inhomogeneous condensate.

Shyamal Biswas, Saugata Bhattacharyya, Amit Agarwal

Abstract We explore the Casimir effect on an interacting Bose–Einstein condensate (BEC) inside a cylindrical tube. The Casimir force for the confined BEC consists of (i) a mean-field part arising from the spatial inhomogeneity of the condensate order parameter, and (ii) a quantum fluctuation part arising from the confinement of Bogoliubov excitations in the condensate. Our analytical result predicts Casimir force on a cylindrical shallow of 4 He well below the λ -point, and can be tested experimentally.

Katz, Gcrshnable, Rowen +1 more