Quantum Tunneling of a Macroscopic Matter-wave Soliton

Kimberley Anne Heenan, Mario Salerno, Tristram J. Alexander +1 more

John H. Miller

Luca Salasnich, Alberto Parola, L. Reatto

We investigate the dynamics of Bose-Einstein condensate bright solitons made of alkali-metal atoms with negative scattering length and under harmonic confinement in the transverse direction. Contrary to the one-dimensional (1D) case, the 3D bright soliton exists only below a critical attractive interaction that depends on the extent of confinement. Such a behavior is also found in multisoliton condensates with box boundary conditions. We obtain numerical and analytical estimates of the critical strength beyond which the solitons do not exist. By using an effective 1D nonpolynomial nonlinear Schr\"odinger equation, which accurately takes into account the transverse dynamics of cigarlike condensates, we numerically simulate the dynamics of the ``soliton train'' reported in a recent experiment [Nature (London) 417, 150 (2002)]. Then, analyzing the macroscopic quantum tunneling of the bright soliton on a Gaussian barrier, we find that its interference in the tunneling region is strongly suppressed with respect to nonsolitonic case; moreover, the tunneling through a barrier breaks the shape invariance of the matter wave. Finally, we show that the collapse of the soliton is induced by the scattering on the barrier or by the collision with another matter wave when the density reaches a critical value, for which we derive an accurate analytical formula.

Chaohong Lee, Elena A. Ostrovskaya, Yuri S. Kivshar

We investigate the {\em nonlinearity-assisted quantum tunneling} and formation of nonlinear collective excitations in a matter-wave interferometer, which is realised by the adiabatic transformation of a double-well potential into a single-well harmonic trap. In contrast to the linear quantum tunneling induced by the crossing (or avoided crossing) of neighbouring energy levels, the quantum tunneling between different nonlinear eigenstates is assisted by the nonlinear mean-field interaction. When the barrier between the wells decreases, the mean-field interaction aids quantum tunneling between the ground and excited nonlinear eigenstates. The resulting {\em non-adiabatic evolution} depends on the input states. The tunneling process leads to the generation of dark solitons, and the number of the generated dark solitons is highly sensitive to the matter-wave nonlinearity. The results of the numerical simulations of the matter-wave dynamics are successfully interpreted with a coupled-mode theory for multiple nonlinear eigenstates.

Simon L. Cornish, Nicholas G. Parker, A. Martin +4 more

Chaohong Lee, Elena A. Ostrovskaya, Yuri S. Kivshar

We investigate the nonlinearity-assisted quantum tunnelling and formation of nonlinear collective excitations in a matter-wave interferometer, which is realized by the adiabatic transformation of a double-well potential into a single-well harmonic trap. In contrast to the linear quantum tunnelling induced by the crossing (or avoided crossing) of neighbouring energy levels, the quantum tunnelling between different nonlinear eigenstates is assisted by the nonlinear mean-field interaction. When the barrier between the wells decreases, the mean-field interaction aids quantum tunnelling between the ground and excited nonlinear eigenstates. The resulting non-adiabatic evolution depends on the input states. The tunnelling process leads to the generation of dark solitons, and the number of the generated dark solitons is highly sensitive to the matter-wave nonlinearity. The results of the numerical simulations of the matter-wave dynamics are successfully interpreted with a coupled-mode theory for multiple nonlinear eigenstates.