Intrinsic and emergent anomalies at deconfined critical points

Max A. Metlitski and Ryan Thorngren
Phys. Rev. B 98, 085140 – Published 24 August 2018

Abstract

It is well known that theorems of Lieb-Schultz-Mattis type prohibit the existence of a trivial symmetric gapped ground state in certain systems possessing a combination of internal and lattice symmetries. In the continuum description of such systems, the Lieb-Schultz-Mattis theorem is manifested in the form of a quantum anomaly afflicting the symmetry. We demonstrate this phenomenon in the context of the deconfined critical point between a Neel state and a valence bond solid in an S=1/2 square lattice antiferromagnet and compare it to the case of S=1/2 honeycomb lattice where no anomaly is present. We also point out that new anomalies, unrelated to the microscopic Lieb-Schultz-Mattis theorem, can emerge, prohibiting the existence of a trivial gapped state in the immediate vicinity of critical points or phases. For instance, no translationally invariant weak perturbation of the S=1/2 gapless spin chain can open up a trivial gap even if the spin-rotation symmetry is explicitly broken. The same result holds for the S=1/2 deconfined critical point on a square lattice.

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  • Received 24 June 2018

DOI:https://doi.org/10.1103/PhysRevB.98.085140

©2018 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Max A. Metlitski1 and Ryan Thorngren2

  • 1Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
  • 2Department of Mathematics, University of California, Berkeley, California 94720, USA

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Issue

Vol. 98, Iss. 8 — 15 August 2018

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