Phase diagram of spin-1/2 bosons in one-dimensional optical lattice

TL;DR

This paper maps the phase diagram of spin-1/2 bosons in a one-dimensional optical lattice, revealing how population balance and magnetic properties depend on interaction sign and phase (superfluid or Mott insulator).

Contribution

It provides a detailed phase diagram analysis using Mean Field Theory and Quantum Monte Carlo, highlighting population and magnetic behaviors across different phases and interaction strengths.

Findings

Population balance in negative spin interactions

Polarized superfluid phase with positive interactions

Balanced populations in even Mott insulators

Abstract

Systems of two coupled bosonic species are studied using Mean Field Theory and Quantum Monte Carlo. The phase diagram is characterized both based on the mobility of the particles (Mott insulating or superfluid) and whether or not the system is magnetic (different populations for the two species). The phase diagram is shown to be population balanced for negative spin-dependent interactions, regardless of whether it is insulating or superfluid. For positive spin-dependent interactions, the superfluid phase is always polarized, the two populations are imbalanced. On the other hand, the Mott insulating phase with even commensurate filling has balanced populations while the odd commensurate filling Mott phase has balanced populations at very strong interaction and polarizes as the interaction gets weaker while still in the Mott phase.