Ferroelectric quantum phase transition with cold polar molecules

TL;DR

This paper investigates a quantum phase transition to a ferroelectric phase in a one-dimensional system of polar molecules manipulated by electric and microwave fields, revealing long-range dipole order.

Contribution

It demonstrates the emergence of a ferroelectric phase via a $U(1)$ symmetry breaking, combining mean-field analysis with Bose-Hubbard and bosonization techniques.

Findings

Identification of a ferroelectric quantum phase transition.

Verification of phase diagram through multiple theoretical methods.

Characterization of long-range order in electric dipole moments.

Abstract

We analyze a system of polar molecules in a one-dimensional optical lattice. By controlling the internal structure of the polar molecules with static electric and microwave fields, we demonstrate the appearance of a quantum phase transition into a ferroelectric phase via spontaneous breaking of a $U(1)$ symmetry. The phase diagram is first analyzed within mean-field theory, while in a second step the results are verified by a mapping onto the Bose-Hubbard model for hard-core bosons. The latter is studied within the well-established bosonization procedure. We find that the ferroelectric phase is characterized by (quasi) long-range order for the electric dipole moments.