paper

Fracton physics of spatially extended excitations. II. Polynomial ground state degeneracy of exactly solvable models

arXiv:2104.05735 · doi:10.1103/PhysRevB.104.235127

Abstract

Generally, ``fracton'' topological orders are referred to as gapped phases that support \textit{point-like topological excitations} whose mobility is, to some extent, restricted. In our previous work [Phys. Rev. B 101, 245134 (2020)], a large class of exactly solvable models on hypercubic lattices are constructed. In these models, \textit{spatially extended excitations} possess generalized fracton-like properties: not only mobility but also deformability is restricted. As a series work, in this paper, we proceed further to compute ground state degeneracy (GSD) in both isotropic and anisotropic lattices. We decompose and reconstruct ground states through a consistent collection of subsystem ground state sectors, in which mathematical game ``coloring method'' is applied. Finally, we are able to systematically obtain GSD formulas (expressed as ) which exhibit diverse kinds of polynomial dependence on system sizes. For example, the GSD of the model labeled as in four dimensional isotropic hypercubic lattice shows dependence on the linear size of the lattice. Inspired by existing results [Phys. Rev. X 8, 031051 (2018)], we expect that the polynomial formulas encode geometrical and topological fingerprints of higher-dimensional manifolds beyond toric manifolds used in this work. This is left to future investigation.

See also: arXiv:1909.02814; Accepted by Phys. Rev. B

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