Majorana spin liquids on a two-leg ladder

Hsin-Hua Lai and Olexei I. Motrunich
Phys. Rev. B 84, 235148 – Published 27 December 2011

Abstract

We realize a gapless Majorana orbital liquid (MOL) using orbital degrees of freedom and an SU(2)-invariant Majorana spin liquid (MSL) using both spin and orbital degrees of freedom in Kitaev-type models on a two-leg ladder. The models are exactly solvable by Kitaev's parton approach, and we obtain long-wavelength descriptions for both Majorana liquids. The MOL has one gapless mode and power-law correlations in energy at incommensuate wave vectors, while the SU(2) MSL has three gapless modes and power-law correlations in spin, spin-nematic, and local energy observables. We study the stability of such states to perturbations away from the exactly solvable points. We find that both MOL and MSL can be stable against allowed short-range parton interactions. We also argue that both states persist on allowing Z2 gauge-field fluctuations, in that the number of gapless modes is retained, although with an expanded set of contributions to observables compared to the free parton mean field.

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  • Received 21 October 2011

DOI:https://doi.org/10.1103/PhysRevB.84.235148

©2011 American Physical Society

Authors & Affiliations

Hsin-Hua Lai and Olexei I. Motrunich

  • Department of Physics, California Institute of Technology, Pasadena, California 91125, USA

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Issue

Vol. 84, Iss. 23 — 15 December 2011

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