arXiv:cond-mat/0402558 · New Journal of Physics

Phase dependence of phonon tunnelling in bosonic superfluid–insulator–superfluid junctions

Ippei Danshita, Nobuhiko Yokoshi, Susumu Kurihara

Published Mar 28, 2006• 38 citations

Abstract

We consider the tunnelling of phonon excitations across a potential barrier spatially separating two condensates with different macroscopic phases. We analyse the relation between the phase difference φ of the two condensates and the transmission coefficient T by solving the Bogoliubov equations. It is found that T strongly depends on φ, and that the perfect transmission of low-energy excitations disappears when the phase difference reaches the critical value which gives the maximum supercurrent of the condensate. We also discuss the feasibility of observing the phase differences in experiments.

DOI: 10.1088/1367-2630/8/3/044

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arXiv:cond-mat/0402558 · New Journal of Physics

Phase dependence of phonon tunnelling in bosonic superfluid–insulator–superfluid junctions

Ippei Danshita, Nobuhiko Yokoshi, Susumu Kurihara

Published Mar 28, 2006• 38 citations

arXiv HTML PDF

Abstract

DOI: 10.1088/1367-2630/8/3/044

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(u,v)

of low-energy Bogoliubov phonon has the same form as the condensate wave function in the supercurrent state. As a result, the currents

{J}_{u}

and

{J}_{v}

associated with

u

and

v

, respectively, have the same tunneling properties as those of supercurrent carried by condensate. Thus, the tunneling of low-energy Bogoliubov phonon described by the tunneling of these two currents shows perfect transmission. We also show that the supercurrent behaviors of Bogoliubov phonon still exist in the presence of supercurrent carried by condensate, except in the critical supercurrent state. In the critical current state, the perfect transmission is absent, because

{J}_{u}

{J}_{v}

exceeds their upper limit given by the critical value of the supercurrent associated with the condensate. Our results consistently explain the recently proposed two tunneling phenomena associated with Bogoliubov phonon, namely, the anomalous tunneling effect (perfect transmission in the low-energy limit) and the breakdown of the perfect transmission in the critical supercurrent state.

ε

. Moreover, the transmission is reduced with increasing

ε

in contrast to the standard dependence. This anomalous behavior is due to an existence of the quasiresonance interaction. The origin of this interaction is a result of the formation of the special well determined by the density distribution of condensate in the vicinity of a high barrier.