Super Solid Categories

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Introduction

Motivation

The purpose of this page is to attempt a categorization of the various phases called ``supersolid, and to sort different physical systems into those categories.

Definition

A supersolid is a system showing spontaneously broken translational symmetry (the solid), coexisting with superfluidity, or alternatively broken gauge symmetry.

Categories

I. Continuum supersolids

Category I supersolids are continuos space systems, were a continuous translation symmetry is broken down to a discrete symmetry.

I.A Single species supersolids

I.A.1 Andreev-Lifshitz type

Definition: few atoms per unit cell in the solid, and superfluidity of vacancies and interstitials

Examples: none known

I.A.2 Gross type

Definition: superfluid droplets forming a crystal

Examples:

  • ...
  • ...


I.B Multi-component supersolids

I.B.1 Purely bosonic mixtures

Definition: a mixture of bosonic particles

Examples:

  • any known?

I.B.2 Bose-fermi mixtures with superfluid bosons

Definition: a mixture of bosonic and fermionic particles, where only bosonic particles become superfluid

Examples:

  • any known?

I.B.2 Mixtures with superfluid fermions

Definition: a mixture of bosonic and fermionic species, where some of the fermions form superfluid Cooper pairs

Examples:

  • all superconducting crystals

II. Lattice supersolids

Category II supersolids are lattice systems, were a discrete translation symmetry is spontaneously broken down further,

II.A Single species supersolids

II.A.1 Andreev-Lifshitz type

Definition: few atoms per unit cell in the solid, and superfluidity of vacancies and interstitials

Examples:

  • bosons with nearest neighbor or dipolar repulsion on a triangular lattice
  • bosons with nearest neighbor repulsion on a face centered cubic lattice

II.A.2 Gross type

Definition: superfluid droplets forming a crystal

Examples:

  • ...
  • ...

II.B Multi-component supersolids

II.B.1 Purely bosonic mixtures

Definition: a mixture of bosonic particles

Examples:

  • two-species bosonic mixtures on a square or cubic lattice

II.B.2 Bose-fermi mixtures with superfluid bosons

Definition: a mixture of bosonic and fermionic particles, where only bosonic particles become superfluid

Examples:

  • Büchler-Blatter

II.B.2 Mixtures with superfluid fermions

Definition: a mixture of bosonic and fermionic species, where some of the fermions form superfluid Cooper pairs

Examples:

  • any known?

= III. Other supersolids

Non-supersolids

While there is a broad scope for interpretation, there are a number of systems that cannot be labeled a supersolid. These include the systems discussed below

Phase separation

Some systems separate into solid and superfluid phases in different regions of space. Even if it is the same component this cannot be called a supersolid.