arXiv subjects

S. L. Cornish

Publications and source records attributed to S. L. Cornish.

33 records · Page 2Linked to original sources

arXiv2010

Realizing bright matter-wave soliton collisions with controlled relative phase

We propose a method to split the ground state of an attractively interacting atomic Bose-Einstein condensate into two bright solitary waves with controlled relative phase and velocity. We analyze the stability of these waves against their subsequent re-collisions at the center of a cylindrically symmetric, prolate harmonic trap as a function of relative phase, velocity, and trap anisotropy. We show that the collisional stability is strongly dependent on relative phase at low velocity, and we identify previously unobserved oscillations in the collisional stability as a function of the trap anisotropy. An experimental implementation of our method would determine the validity of the mean field description of bright solitary waves, and could prove an important step towards atom interferometry experiments involving bright solitary waves.

cond-mat.quant-gas↗

arXiv2008

Collapse times of dipolar Bose-Einstein condensates

We investigate the time taken for global collapse by a dipolar Bose-Einstein condensate. Two semi-analytical approaches and exact numerical integration of the mean-field dynamics are considered. The semi-analytical approaches are based on a Gaussian ansatz and a Thomas-Fermi solution for the shape of the condensate. The regimes of validity for these two approaches are determined, and their predictions for the collapse time revealed and compared with numerical simulations. The dipolar interactions introduce anisotropy into the collapse dynamics and predominantly lead to collapse in the plane perpendicular to the axis of polarization.

cond-mat.other↗

arXiv2008

Modulation transfer spectroscopy in atomic rubidium

We report modulation transfer spectroscopy on the D2 transitions in 85Rb and 87Rb using a simple home-built electro-optic modulator (EOM). We show that both the gradient and amplitude of modulation transfer spectroscopy signals, for the 87Rb F=2 to F'=3 and the 85Rb F=3 to F'=4 transitions, can be significantly enhanced by expanding the beams, improving the signals for laser frequency stabilization. The signal gradient for these transitions is increased by a factor of 3 and the peak to peak amplitude was increased by a factor of 2. The modulation transfer signal for the 85Rb F=2 to F' transitions is also presented to highlight how this technique can generate a single, clear line for laser frequency stabilization even in cases where there are a number of closely spaced hyperfine transitions.

physics.atom-ph↗

arXiv2008

Quantum reflection of bright matter-wave solitons

We propose the use of bright matter-wave solitons formed from Bose-Einstein condensates with attractive interactions to probe and study quantum reflection from a solid surface at normal incidence. We demonstrate that the presence of attractive interatomic interactions leads to a number of advantages for the study of quantum reflection. The absence of dispersion as the soliton propagates allows precise control of the velocity normal to the surface and for much lower velocities to be achieved. Numerical modelling shows that the robust, self-trapped nature of bright solitons leads to a clean reflection from the surface, limiting the disruption of the density profile and permitting accurate measurements of the reflection probability.

quant-ph↗

arXiv2008

Bright solitary waves of trapped atomic Bose-Einstein condensates

Motivated by recent experimental observations, we study theoretically multiple bright solitary waves of trapped Bose-Einstein condensates. Through variational and numerical analyses, we determine the threshold for collapse of these states. Under $π$-phase differences between adjacent waves, we show that the experimental states lie consistently at the threshold for collapse, where the corresponding in-phase states are highly unstable. Following the observation of two long-lived solitary waves in a trap, we perform detailed three-dimensional simulations which confirm that in-phase waves undergo collapse while a $π$-phase difference preserves the long-lived dynamics and gives excellent quantitative agreement with experiment. Furthermore, intermediate phase differences lead to the growth of population asymmetries between the waves, which ultimately triggers collapse.

cond-mat.other↗

arXiv2008

Magnetic trapping of a cold Rb-Cs atomic mixture

We present an apparatus for the study of an ultracold gaseous atomic mixture of 133Cs and 87Rb. The mixture is prepared using a double magneto-optical trap (MOT) system in which a two-species pyramid MOT acts as a source of cold atoms for a `science' MOT. Measurements of the interspecies trap loss rate coefficients beta_RbCs and beta_CsRb in the science MOT are reported. After the initial MOT phase, atoms in the mixture are optically pumped into the magnetically trappable |F=3,m_F=-3> and |F=1,m_F=-1> states of Cs and Rb (respectively) and loaded into an Ioffe-Pritchard magnetic trap. We demonstrate a novel technique for limiting the interspecies loss rate in the science MOT by spatially separating the two trapped atom clouds, which greatly enhances the number of atoms which can be loaded into the magnetic trap.

cond-mat.other↗

arXiv2007

Collisions of bright solitary matter waves

The collisions of three-dimensional bright solitary matter waves formed from atomic Bose-Einstein condensates are shown to exhibit rich behaviour. Collisions range from being elastic to completely destructive due to the onset of collapse during the interaction. Through a detailed quantitative analysis we map out the role of relative phase, impact speed and interaction strength. In particular, we identify the importance of the collapse time in the onset of unstable collisions and show how the relative phase controls a population transfer between the waves. Our analysis enables us to interpret recent experimental observations of bright solitary matter waves.

cond-mat.other↗

arXiv2007

Bright solitary waves and trapped solutions in Bose-Einstein condensates with attractive interactions

We analyse the static solutions of attractive Bose-Einstein condensates under transverse confinement, both with and without axial confinement. By full numerical solution of the Gross-Pitaevskii equation and variational methods we map out the condensate solutions, their energetic properties, and their critical points for instability. With no axial confinement a bright solitary wave solution will tend to decay by dispersion unless the interaction energy is close to the critical value for collapse. In contrast, with axial confinement the only decay mechanism is collapse. The stability of a bright solitary wave solution increases with higher radial confinement. Finally we consider the stability of dynamical states containing up to four solitons and find good agreement with recent experiments.

cond-mat.other↗

arXiv2006

Polarization spectroscopy in rubidium and cesium

We develop a theoretical treatment of polarization spectroscopy and use it to make predictions about the general form of polarization spectra in the alkali atoms. Using our model, we generate theoretical spectra for the D2 transitions in 87Rb, 85Rb, and 133Cs. Experiments demonstrate that the model accurately reproduces spectra of transitions from the upper hyperfine level of the ground state only. Among these, the closed transition F -> F' = F + 1 dominates, with a steep gradient through line center ideally suited for use as a reference in laser locking.

physics.atom-ph↗

arXiv2006

Collisions between solitary waves of three-dimensional Bose-Einstein condensates

We study bright solitary waves of three dimensional trapped Bose-Einstein condensates and their collisions. For a single solitary wave, in addition to an upper critical number, we also find a {\em lower} cut-off, below which no stable state can be found. Collisions between solitary waves can be elastic, inelastic with either reduced or increased outgoing speed, or completely unstable due to a collapse instability. A $π$-phase difference between the waves promotes elastic collisions, and gives excellent agreement with recent experimental results over long timescales.

cond-mat.other↗

arXiv2001

Improved Characterization of Elastic Scattering Near a Feshbach Resonance in 85Rb

We report extentions and corrections to the measurement of the Feshbach resonance in 85Rb cold atom collisions reported earlier [J. L. Roberts et al., Phys. Rev. Lett. 81, 5109 (1998)]. In addition to a better determination of the position of the resonance peak (154.9(4) gauss) and its width (11.0(4) gauss), improvements in our techniques now allow the measurement of the absolute size of the elastic scattering rate. This provides a new measure of the s-wave scasttering length as a function of magnetic field near the Feshbach resonance and contrains the Rb-Rb interaction potential.

physics.atom-ph↗

arXiv2001

Controlled Collapse of a Bose-Einstein Condensate

The point of instability of a Bose-Einstein Condensate (BEC) due to attractive interactions was studied. Stable 85-Rb BECs were created and then caused to collapse by slowly changing the atom-atom interaction from repulsive to attractive using a Feshbach resonance. At a critical value, an abrupt transition was observed in which atoms were ejected from the condensate. By measuring the onset of this transition as a funstion of number and attractive interactions strength, we determined the stability condition to be N|a|/(aho)=0.461(12)(54), slightly lower than the predicted value of 0.574.

cond-mat.stat-mech↗

arXiv2000

Stable 85Rb Bose-Einstein Condensates with Widely Tunable Interactions

Bose-Einstein condensation has been achieved in a magnetically trapped sample of 85Rb atoms. Long-lived condensates of up to 10^4 atoms have been produced by using a magnetic-field-induced Feshbach resonance to reverse the sign of the scattering length. This system provides many unique opportunities for the study of condensate physics. The variation of the scattering length near the resonance has been used to magnetically tune the condensate self-interaction energy over a very wide range. This range extended from very strong repulsive to large attractive self-interactions. When the interactions were switched from repulsive to attractive, the condensate shrank to below our resolution limit, and after ~5 ms emitted a burst of high-energy atoms.

cond-mat↗

arXiv2000

Magnetic Field Dependence of Ultracold Inelastic Collisions near a Feshbach Resonance

Inelastic collision rates for ultracold $^{85}$Rb atoms in the F=2 m$_{f}$=-2 state have been measured as a function of magnetic field. Dramatic change in the vicinity of a Feshbach resonance at 155 G was observed. Similar to the elastic rate, the inelastic rates show a high peak and a deep trough. Both two- and three-body processes are important, and individual contributions have been determined and compared with theory. This work has made it possible to create an $^{85}$Rb Bose-Einstein condensate with a highly adjustable scattering length.

physics.atom-ph↗

arXiv1999

Measurement of the 1s-2s energy interval in muonium

The 1s-2s interval has been measured in the muonium ({$μ^+e^-$}) atom by Doppler-free two-photon laser spectroscopy. The frequency separation of the states was determined to be 2 455 528 941.0(9.8) MHz in good agreement with quantum electrodynamics. The muon-electron mass ratio can be extracted and is found to be 206.768 38(17). The result may be interpreted as measurement of the muon-electron charge ratio as $-1- 1.1(2.1)\cdot 10^{-9}$.

hep-ex↗