A fracton is an emergent topological quasiparticle excitation which is immobile when in isolation.[1][2] Many theoretical systems have been proposed in which fractons exist as elementary excitations. Such systems are known as fracton models. Fractons have been identified in various CSS codes as well as in symmetric tensor gauge theories.
Gapped fracton models often feature a topological ground state degeneracy that grows exponentially and sub-extensively with system size. Among the gapped phases of fracton models, there is a non-rigorous phenomenological classification into "type I" and "type II". Type I fracton models generally have fracton excitations that are completely immobile, as well as other excitations, including bound states, with restricted mobility. Type II fracton models generally have fracton excitations and no mobile particles of any form. Furthermore, isolated fracton particles in type II models are associated with nonlocal operators with intricate fractal structure.[3]
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- ^ Nandkishore, Rahul M; Hermele, Michael (2019). "Fractons". Annual Review of Condensed Matter Physics. 10: 295–313. arXiv:1803.11196. Bibcode:2019ARCMP..10..295N. doi:10.1146/annurev-conmatphys-031218-013604. S2CID 242949983.
- ^ Pretko, Michael; Chen, Xie; You, Yizhi (2020). "Fracton Phases of Matter". International Journal of Modern Physics A. 35 (6). arXiv:2001.01722. Bibcode:2020IJMPA..3530003P. doi:10.1142/s0217751x20300033. S2CID 210023393.