Rotating molecules in optical lattices, alignment and monopole crystals

TL;DR

This paper explores how the orientation of molecules in optical lattices affects their behavior, revealing phenomena like anisotropic superfluidity and pseudo-magnetic monopoles depending on laser coherence and rotational level splitting.

Contribution

It introduces a theoretical framework for understanding molecular orientation effects in optical lattices, including the emergence of geometric vector potentials and monopole-like structures.

Findings

Incoherent lasers preserve molecular orientation, enabling anisotropic superfluidity.

Coherent lasers with large rotational splitting lead to geometric vector potentials and monopoles.

Frustrated band structures with degenerate minima are predicted under certain conditions.

Abstract

The recent progress towards production of near-ground state quantum-degenerate molecules raises the issue of how such "small" molecules behave in an optical lattice. In this Letter we show that the coupling of the molecular orientation to the local electric field direction will provide severalnew phenomena. In the case where the lasers forming different crystallographic directions of the lattice are incoherent, the orientation of the molecules is conserved (for L = 1) and a novel form of anisotropic superfluidity can be expected. When the lasers are coherent, and the optical lattice is such that the splitting of the rotational levels is large compared to the centre of mass energies,an adiabaic description of the molecular orientation is appropriate. This leads to geometric vector potentials, pseudo-magnetic monopoles and a frustrated band structure with degenerate minima.