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arXiv · 2101.00268

Stripping the planar Quantum Compass Model to its basics

Soumya Sur·M. S. Laad·S. R. Hassan
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Abstract

We introduce a novel mean-field theory (MFT) around the exactly soluble two-leg ladder limit for the planar quantum compass model (QCM). In contrast to usual MFT, our construction respects the stringent constraints imposed by emergent, lower (here $d=1$) dimensional symmetries of the QCM. Specializing our construction to the QCM on a periodic four-leg ladder, we find that a first-order transition separates two mutually dual Ising nematic phases, in good accord with state-of-the-art numerics for the planar QCM. One pseudo-spin-flip excitation in the ordered phase turns out to be two (Jordan-Wigner) fermion bound states, reminiscent of spin waves in spin-$1/2$ Heisenberg chains. We discuss the novel implications of our work on (1) the emergence of coupled orbital and magnetic ordered and liquidlike disordered phases, and (2) a rare instance of orbital-spin separation in $d>1$, in the context of a Kugel-Khomskii view of multi-orbital Mott insulators.

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Soumya Sur, M. S. Laad, S. R. Hassan. 2021-01-01. Stripping the planar Quantum Compass Model to its basics. https://doi.org/10.1103/physrevb.103.144419

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