Dipolar Bose-Einstein Condensates

Ryan Wilson, Shai Ronen, John L. Bohn

We explore the structure and dynamics of dipolar Bose-Einstein condensates (DBECs) near their threshold for instability. Near this threshold a DBEC may exhibit nontrivial biconcave density distributions, which are associated with instability against collapse into ``angular roton'' modes. Here we discuss experimental signatures of these features. In the first, we infer local collapse of the DBEC from the experimental stability diagram. In the second, we explore the dynamics of collapse and find that a nontrivial angular distribution is a signature of the DBEC possessing a biconcave structure.

Juergen Stuhler, Axel Griesmaier, M. Fattori +4 more

F. Wächtler, Luis Santos

The ground state of dipolar Bose-Einstein condensates (BEC) is studied in the regimes of three different phases, where a characteristic growth of the peak density of the BEC is predicted when the dipolar quantum droplets are formed.

Yuki Kawaguchi, Hiroki Saito, Masahito Ueda

Alberto Villois, Miguel Onorato, Davide Proment

Dipolar Bose-Einstein condensates (dBECs) exhibit a plethora of physics phenomena, from supersolidity to the rotonlike minimum in the elementary excitation spectrum. In this work we first demonstrate the existence of axis-symmetric solitary waves in (quasi-)two-dimensional dBECs: these localized excitations are characterized by quantized vortex dipoles that continuously transit to vortex-free density depletions. We then show how the presence of the roton minimum fundamentally alters the fate of such solutions when approaching Landau’s critical speed: when propagating along the polarization direction where the roton minimum occurs, the solitary wave transits into roton excitations rather than into phonons as for standard contact-interaction BECs. This finding suggests that Feynman’s hypothesis, conjectured for 3D superfluid liquid helium regarding the creation of rotons as fading vortex excitations, is valid in the context of 2D dBECs.

Jing-Min Hou, Tiantao Zhao, Lijie Zhang