Robert L. D. Campbell

Publications (7)22.11 Total impact

• Article: A compact single-chamber apparatus for Bose-Einstein condensation of $^87$Rb

  Igor Gotlibovych, Tobias F. Schmidutz, Stuart Moulder, Robert L. D. Campbell, Naaman Tammuz, Richard J. Fletcher, Alexander L. Gaunt, Scott Beattie, Robert P. Smith, Zoran Hadzibabic
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  ABSTRACT: We describe a simple and compact single-chamber apparatus for robust production of $^87$Rb Bose-Einstein condensates. The apparatus is built from off-the-shelf components and allows production of quasi-pure condensates of > $3\times 10^5$ atoms in < 30 s. This is achieved using a hybrid trap created by a quadrupole magnetic field and a single red-detuned laser beam [Y.-J. Lin et al., Phys. Rev. A 79, 063631 (2009)]. In the same apparatus we also achieve condensation in an optically plugged quadrupole trap [K. B. Davis et al., Phys. Rev. Lett. 75, 3969 (1995)] and show that as little as 70 mW of plug-laser power is sufficient for condensation, making it viable to pursue this approach using inexpensive diode lasers. While very compact, our apparatus features sufficient optical access for complex experiments, and we have recently used it to demonstrate condensation in a uniform optical-box potential [A. Gaunt et al., arXiv:1212.4453 (2012)].
  12/2012;
• Source

  Available from: ArXiv

  Article: Condensation dynamics in a quantum-quenched Bose gas

  Robert P. Smith, Scott Beattie, Stuart Moulder, Robert L. D. Campbell, Zoran Hadzibabic
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  ABSTRACT: By quenching the strength of interactions in a partially condensed Bose gas we create a "super-saturated" vapor which has more thermal atoms than it can contain in equilibrium. Subsequently, the number of condensed atoms ($N_0$) grows even though the temperature ($T$) rises and the total atom number decays. We show that the non-equilibrium evolution of the system is isoenergetic and for small initial $N_0$ observe a clear separation between $T$ and $N_0$ dynamics, thus explicitly demonstrating the theoretically expected "two-step" picture of condensate growth. For increasing initial $N_0$ values we observe a crossover to classical relaxation dynamics. The size of the observed quench-induced effects can be explained using a simple equation of state for an interacting harmonically-trapped atomic gas.
  12/2011;
• Source

  Available from: ArXiv

  Article: Condensed fraction of an atomic Bose gas induced by critical correlations.

  Robert P Smith, Naaman Tammuz, Robert L D Campbell, Markus Holzmann, Zoran Hadzibabic
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  ABSTRACT: We study the condensed fraction of a harmonically trapped atomic Bose gas at the critical point predicted by mean-field theory. The nonzero condensed fraction f(0) is induced by critical correlations which increase the transition temperature T(c) above T(c) (MF). Unlike the T(c) shift in a trapped gas, f(0) is sensitive only to the critical behavior in the quasiuniform part of the cloud near the trap center. To leading order in the interaction parameter a/λ(0), where a is the s-wave scattering length and λ(0) the thermal wavelength, we expect a universal scaling f(0) proportionally (a/λ(0))(4). We experimentally verify this scaling using a Feshbach resonance to tune a/λ(0). Further, using the local density approximation, we compare our measurements with the universal result obtained from Monte Carlo simulations for a uniform system, and find excellent quantitative agreement.
  Physical Review Letters 11/2011; 107(19):190403. · 7.37 Impact Factor
• Source

  Available from: ArXiv

  Article: Effects of interactions on the critical temperature of a trapped Bose gas.

  Robert P Smith, Robert L D Campbell, Naaman Tammuz, Zoran Hadzibabic
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  ABSTRACT: We perform high-precision measurements of the condensation temperature of a harmonically trapped atomic Bose gas with widely tunable interactions. For weak interactions we observe a negative shift of the critical temperature in excellent agreement with mean-field theory. However for sufficiently strong interactions we clearly observe an additional positive shift, characteristic of beyond-mean-field critical correlations. We also discuss nonequilibrium effects on the apparent critical temperature for both very weak and very strong interactions.
  Physical Review Letters 06/2011; 106(25):250403. · 7.37 Impact Factor
• Article: Can a Bose gas be saturated?

  Naaman Tammuz, Robert P Smith, Robert L D Campbell, Scott Beattie, Stuart Moulder, Jean Dalibard, Zoran Hadzibabic
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  ABSTRACT: We scrutinize the concept of saturation of the thermal component in a partially condensed trapped Bose gas. Using a 39K gas with tunable interactions, we demonstrate strong deviation from Einstein's textbook concept of a saturated vapor. However, the saturation picture can be recovered by extrapolation to the strictly noninteracting limit. We provide evidence for the universality of our observations through additional measurements with a different atomic species, 87Rb.
  Physical Review Letters 06/2011; 106(23):230401. · 7.37 Impact Factor
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  Available from: ArXiv

  Article: Can a Bose gas be saturated?

  Naaman Tammuz, Robert P. Smith, Robert L. D. Campbell, Scott Beattie, Stuart Moulder, Jean Dalibard, Zoran Hadzibabic
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  ABSTRACT: Bose-Einstein condensation is unique among phase transitions between different states of matter in the sense that it occurs even in the absence of interactions between particles. In Einstein's textbook picture of an ideal gas, purely statistical arguments set an upper bound on the number of particles occupying the excited states of the system, and condensation is driven by this saturation of the quantum vapour. Dilute ultracold atomic gases are celebrated as a realisation of Bose-Einstein condensation in close to its purely statistical form. Here we scrutinise this point of view using an ultracold gas of potassium (39K) atoms, in which the strength of interactions can be tuned via a Feshbach scattering resonance. We first show that under typical experi-mental conditions a partially condensed atomic gas strongly deviates from the textbook concept of a saturated vapour. We then use measurements at a range of interaction strengths and temperatures to extrapolate to the non-interacting limit, and prove that in this limit the behaviour of a Bose gas is consistent with the saturation picture. Finally, we provide evidence for the universality of our observations through additional measurements with a different atomic species, 87Rb. Our results suggest a new way of characterising condensation phenomena in different physical systems.
  03/2011;
• Source

  Available from: ArXiv

  Article: Efficient Production of Large 39K Bose-Einstein Condensates

  Robert L. D. Campbell, Robert P. Smith, Naaman Tammuz, Scott Beattie, Stuart Moulder, Zoran Hadzibabic
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  ABSTRACT: We describe an experimental setup and the cooling procedure for producing 39K Bose-Einstein condensates of over 4x10^5 atoms. Condensation is achieved via a combination of sympathetic cooling with 87Rb in a quadrupole-Ioffe-configuration (QUIC) magnetic trap, and direct evaporation in a large volume crossed optical dipole trap, where we exploit the broad Feshbach resonance at 402 G to tune the 39K interactions from weak and attractive to strong and repulsive. In the same apparatus we create quasi-pure 87Rb condensates of over 8x10^5 atoms. Comment: 7 pages, 5 figures; figure font compatibility improved
  10/2010;