Quantum Phase Transitions and Continuous Observation of Spinor Dynamics in an Antiferromagnetic Condensate

TL;DR

This paper investigates spinor dynamics and phase transitions in an antiferromagnetic spin-1 sodium condensate using continuous Faraday rotation spectroscopy and Stern-Gerlach imaging, revealing a magnetically tuned separatrix and a low-temperature phase transition.

Contribution

It introduces a minimally destructive measurement technique for real-time spin dynamics and identifies a quantum phase transition in the condensate.

Findings

Detection of a magnetically tuned separatrix in phase space

Observation of a phase transition from two- to three-component condensate

Continuous measurement of spin oscillations over multiple cycles

Abstract

Condensates of spin-1 sodium display rich spin dynamics due to the antiferromagnetic nature of the interactions in this system. We use Faraday rotation spectroscopy to make a continuous and minimally destructive measurement of the dynamics over multiple spin oscillations on a single evolving condensate. This method provides a sharp signature to locate a magnetically tuned separatrix in phase space which depends on the net magnetization. We also observe a phase transition from a two- to a three-component condensate at a low but finite temperature using a Stern-Gerlach imaging technique. This transition should be preserved as a zero-temperature quantum phase transition.