Spin supersolid phase in coupled alternating spin chains

TL;DR

This paper explores the phase diagram of a 2D mixed-spin system with coupled alternating spin chains, revealing a stripe supersolid phase and other complex states through analytical and numerical methods.

Contribution

It identifies minimal models for stripe supersolidity in coupled mixed-spin chains, highlighting the roles of interactions and anisotropies.

Findings

Discovery of a stripe supersolid phase in the system.

Necessity of intra-chain repulsive interactions for supersolidity.

Minimal models include coupled XXZ and Ising chains depending on anisotropy.

Abstract

We study the ground state phase diagram of a two dimensional mixed-spin system of coupled alternating spin-1 and $1/2$ chains with a stripe supersolid phase. Utilizing different analytical and numerical approaches such as mean field approximation, cluster mean field theory and linear spin wave theory, we demonstrate that our system displays a rich ground state phase diagram including novel stripe supersolid, solids with different fillings and super-counterfluid phases, in addition to a stripe solid with half filling, superfluid and Mott insulating phases. In order to find a minimal mixed-spin model for stripe supersolidity, in the second part of the paper we consider two kinds of mixed-spin system of coupled alternating spin-1 and $1/2$ chains with (i) anisotropic nearest neighbor interactions, (ii) anisotropic hoppings and study their ground state phase diagrams. We demonstrate that, for the systems with uniform hoppings, the repulsive intra-chains interactions are necessary for stripe supersolidity. In this case the minimal two dimensional mixed-spin model is a system of spin-1 and spin-1/2 XXZ chains, interacting via a XY Hamiltonian. In the case of anisotropic hoppings, a system of coupled Ising chains is the minimal model.