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Lattice Homotopy Constraints on Phases of Quantum Magnets

Cornell Affiliated Author(s)

Author

Hoi Po
Haruki Watanabe
Chao-Ming Jian
Michael Zaletel

Abstract

The Lieb-Schultz-Mattis (LSM) theorem and its extensions forbid trivial phases from arising in certain quantum magnets. Constraining infrared behavior with the ultraviolet data encoded in the microscopic lattice of spins, these theorems tie the absence of spontaneous symmetry breaking to the emergence of exotic phases like quantum spin liquids. In this work, we take a new topological perspective on these theorems, by arguing they originate from an obstruction to "trivializing" the lattice under smooth, symmetric deformations, which we call the "lattice homotopy problem." We conjecture that all LSM-like theorems for quantum magnets (many previously unknown) can be understood from lattice homotopy, which automatically incorporates the full spatial symmetry group of the lattice, including all its point-group symmetries. One consequence is that any spin-symmetric magnet with a half-integer moment on a site with even-order rotational symmetry must be a spin liquid. To substantiate the claim, we prove the conjecture in two dimensions for some physically relevant settings. © 2017 American Physical Society.

Date Published

Journal

Physical Review Letters

Volume

119

Issue

12

URL

https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030155381&doi=10.1103%2fPhysRevLett.119.127202&partnerID=40&md5=6db3b3a4046b249b061ae0167e938e27

DOI

10.1103/PhysRevLett.119.127202

Group (Lab)

Chao-Ming Jian Group

Funding Source

17K17678

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