Instability of Rotationally Tuned Dipolar Bose-Einstein Condensates.

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Gases
• Bose-Einstein Condensates

Background:

• Dipolar Bose-Einstein condensates (BECs) exhibit long-range dipole-dipole interactions, offering unique quantum phenomena.
• Controlling these interactions, particularly their sign, is crucial for engineering novel quantum states and devices.
• Fast rotation of dipole polarization has been proposed as a method to tune these interactions.

Purpose of the Study:

• To examine the feasibility of inverting the sign of dipole-dipole interactions in a harmonically trapped dipolar BEC via fast polarization rotation.
• To investigate the stability of such rotationally tuned states.

Main Methods:

• Analysis of stationary states in the Thomas-Fermi limit within a corotating frame.
• Direct numerical simulations of the BEC dynamics, explicitly including rotating polarization.
• Investigation of collective mode stability.

Main Results:

• The harmonically trapped dipolar BEC is found to be inherently unstable when subjected to fast polarization rotation.
• Dynamical instability of collective modes prevents the formation of robust and long-lived rotationally tuned states.
• The proposed method for inverting dipole-dipole interaction signs is shown to be unfeasible under these conditions.

Conclusions:

• The inherent dynamical instability of collective modes in rotating dipolar BECs prevents the realization of stable, sign-inverted dipole-dipole interactions.
• These findings have significant implications for experimental efforts aiming to control and utilize tunable dipole-dipole interactions in BECs.