Bose 2.2 User Manual download pdf (Page 103)

time (ms)

0 ms 0.1 ms 0.2 ms 0.4 ms0.3 ms

0 0.5 1 1.5

2 3

0.5 ms

(a) (c)

(b)

Fig. 6.1, Collapse dynamics of a dBEC in a single round trap:

(a) Experimental

sequence to induce the collapse. Both the programmed ramp (red line) of the

scattering length

(

) and the real ramp taking into account the eddy currents

(blue line) are shown. The stability threshold is

crit

= (15

[35], the

uncertainty being illustrated by the grey zone. (b) Time evolution of the remnant

BEC for diﬀerent values of

hold

: the upper row corresponds to experimental

images taken after TOF and the lower row shows the results of numerical

simulations. (c) Evolution of the atom number in the remnant BEC after TOF

as a function of

hold

, extracted from the measurements (dots) and from the

simulations (line). All ﬁgures are taken from Ref. [36].

Pitaevskii equation. A crucial point in the simulations is to include the three-body atom

losses that occur during the collapse dynamics. Else, the condensate only contracts to a

single point of the numerical grid and no collapse dynamics can be observed. With the

empirically chosen three-body loss rate

= 2 · 10

−40

/s, the simulations reproduce

both the

-wave density pattern after TOF (see the lower row in Fig. 6.1(b)) and the

measured evolution of the atom number N

BEC

hold

) shown in Fig. 6.1(c).

The simulations allow furthermore to reconstruct the in-trap time evolution of the dBEC

after the stability threshold has been passed: First, the dBEC contracts radially, forming

a very thin cigar along the direction of the external magnetic ﬁeld. Then, strong atom

losses occur at the center of the cloud, such that the centripetal force of the dipoles

weakens and the BEC ﬁnally explodes in the radial directions (

x, y

) due to the surplus of

the quantum pressure. Since the atoms at both ends of the cigar are not involved in the

The three-body loss rate L

enters the Gross-Pitaevskii equation, as we show in section 6.2.3.

103

1 2 ... 98 99 100 101 102 103 104 105 106 107 108 ... 154 155

Comments to this Manuals

No comments

Bose 2.2 User Manual Page 103

Comments to this Manuals

Related products and manuals for Soundbar speakers Bose 2.2