arXiv subjects

P. Blair Blakie

Publications and source records attributed to P. Blair Blakie.

22 records · Page 2Linked to original sources

arXiv2007

Raman Spectroscopy of Mott insulator states in optical lattices

We propose and analyse a Raman spectroscopy technique for probing the properties of quantum degenerate bosons in the ground band of an optical lattice. Our formalism describes excitations to higher vibrational bands and is valid for deep lattices where a tight-binding approach can be applied to the describe the initial state of the system. In sufficiently deep lattices, localized states in higher vibrational bands play an important role in the system response, and shifts in resonant frequency of excitation are sensitive to the number of particles per site. We present numerical results of this formalism applied to the case of a uniform lattice deep in the Mott insulator regime.

cond-mat.other↗

arXiv2005

Bragg Spectroscopy of ultracold atoms loaded in an optical lattice

We study Bragg spectroscopy of ultra-cold atoms in one-dimensional optical lattices as a method for probing the excitation spectrum in the Mott insulator phase, in particular the one particle-hole excitation band. Within the framework of perturbation theory we obtain an analytical expression for the dynamic structure factor $S(q,ω)$ and use it to calculate the imparted energy which has shown to be a relevant observable in recent experiments. We test the accuracy of our approximations by comparing them with numerically exact solutions of the Bose-Hubbard model in restricted cases and establish the limits of validity of our linear response analysis. Finally we show that when the system is deep in the Mott insulator regime, its response to the Bragg perturbation is temperature dependent. We suggest that this dependence might be used as a tool to probe temperatures of order of the Mott gap.

cond-mat.stat-mech↗

arXiv2004

The Projected Gross-Pitaevskii Equation for harmonically confined Bose gases

We extend the Projected Gross Pitaevskii equation formalism of Davis et al. [Phys. Rev. Lett. \bf{87}, 160402 (2001)] to the experimentally relevant case of harmonic potentials. We outline a robust and accurate numerical scheme that can efficiently simulate this system. We apply this method to investigate the equilibrium properties of a harmonically trapped three-dimensional Bose gas at finite temperature, and consider the dependence of condensate fraction, position and momentum distributions, and density fluctuations on temperature. We apply the scheme to simulate an evaporative cooling process in which the preferential removal of high energy particles leads to the growth of a Bose-Einstein condensate. We show that a condensate fraction can be inferred during the dynamics even in this non-equilibrium situation.

cond-mat.other↗

arXiv2003

Topological Atom Laser

We demonstrate how a topological atom laser can be realized by output coupling a trapped vortex state with a Raman scattering process. We find a linearized analytic solution from which a generalized resonance condition for Raman output coupling is developed. Using numerical simulations of a two component Gross-Pitaevskii equation in two and three dimensions the output beam from a trapped central vortex state is analyzed for cases of pulsed and continuous coupling where the vortex core is either transverse or parallel to the direction of propagation. We show how the parameters of the Raman light fields control the spatial phase of the output beam.

cond-mat.soft↗