Flux crystals, Majorana metals, and flat bands in exactly solvable spin-orbital liquids

Sreejith Chulliparambil, Lukas Janssen, Matthias Vojta, Hong-Hao Tu, and Urban F. P. Seifert
Phys. Rev. B 103, 075144 – Published 24 February 2021

Abstract

Spin-orbital liquids are quantum disordered states in systems with entangled spin and orbital degrees of freedom. We study exactly solvable spin-orbital models in two dimensions with selected Heisenberg-, Kitaev-, and Γ-type interactions, as well as external magnetic fields. These models realize a variety of spin-orbital-liquid phases featuring dispersing Majorana fermions with Fermi surfaces, nodal Dirac or quadratic band touching points, or full gaps. In particular, we show that Zeeman magnetic fields can stabilize nontrivial flux patterns and induce metamagnetic transitions between states with different topological character. Solvable nearest-neighbor biquadratic spin-orbital perturbations can be tuned to stabilize zero-energy flat bands. We discuss in detail the examples of SO(2)- and SO(3)-symmetric spin-orbital models on the square and honeycomb lattices, and use group-theoretical arguments to generalize to SO(ν)-symmetric models with arbitrary integer ν>1. These results extend the list of exactly solvable models with spin-orbital-liquid ground states and highlight the intriguing general features of such exotic phases. Our models are thus excellent starting points for more realistic modelling of candidate materials.

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  • Received 13 November 2020
  • Revised 4 February 2021
  • Accepted 5 February 2021

DOI:https://doi.org/10.1103/PhysRevB.103.075144

©2021 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Sreejith Chulliparambil1,2, Lukas Janssen1, Matthias Vojta1, Hong-Hao Tu1, and Urban F. P. Seifert1,3

  • 1Institut für Theoretische Physik and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
  • 2Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Straße 38, 01187 Dresden, Germany
  • 3Université de Lyon, ENS de Lyon, Université Claude Bernard, CNRS, Laboratoire de Physique, 69342 Lyon, France

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Issue

Vol. 103, Iss. 7 — 15 February 2021

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