Comment on "Quantum Time Crystals from Hamiltonians with Long-Range Interactions"
Strongly Correlated Electrons
2020-01-31 v1 Quantum Gases
Statistical Mechanics
Quantum Physics
Abstract
In a recent paper (Phys. Rev. Lett. 123, 210602), Kozin and Kyriienko claim to realize "genuine" ground state time crystals by studying models with long-ranged and infinite-body interactions. Here we point out that their models are doubly problematic: they are unrealizable they violate well established principles for defining phases of matter. Indeed with infinite body operators allowed, almost all quantum systems are time crystals. In addition, one of their models is highly unstable and another amounts to isolating, via fine tuning, a single degree of freedom in a many body system--allowing for this elevates the pendulum of Galileo and Huygens to a genuine time crystal.
Cite
@article{arxiv.2001.11037,
title = {Comment on "Quantum Time Crystals from Hamiltonians with Long-Range Interactions"},
author = {Vedika Khemani and Roderich Moessner and S. L. Sondhi},
journal= {arXiv preprint arXiv:2001.11037},
year = {2020}
}
Comments
1.5 pages; Comment on Phys. Rev. Lett. 123, 210602