Bi-polarons in cigar condensates

New paper in PRL: Two polarons squeezed inside a cigar shaped condensate behave totally different than expected.

2018.08.27 | Ole J. Knudsen

A one dimensional cigar causes polaron behaviour to be totally different

When something completely different, e.g. a different atom enters a condensate, the atoms of the condensate are porlarized, causing a new type of "quasi-particle"; a polaron into existence. The study of the behaviour of such two polarons goes way back. In a new paper by Amin Dehkharghani, Artem Volosinev and Nikolaj Thomas Zinner published August 2018 in Physical Review Letters, the authors describe the behaviour of such two bi-polarons when the condensate is squeezed into the shape of a one-dimensional cigar.


Illustration from the paper.


A totally new variational method for handling more than one polaron in one dimension has been developed, and it seems that the interaction between low dimensional polarons is quite different than what is seen if they were caught in a pan cake shaped or spherical condensate of atoms. The theory works for both weak and strong interactions, and even more important: the outer potential keeping the condensate in its place can be taken into account in the description. This means that for the first time it is possible to calculate the effective interaction between two polarons. The study shows that it is not possible to describe the one dimensional physics case by assuming that the interaction is done via sound waves - the so-called Yukawa-theory. Further the study shows that provided the two alien atoms in the condensate are bosons, the eventual state is bound (this is the bi-polaron) while two fermions will not be bound.

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