Emergent moments and random singlet physics in a Majorana spin liquid

Abstract

We exhibit an exactly solvable example of a SU(2) symmetric Majorana spin liquid phase, in which quenched disorder leads to random-singlet phenomenology. More precisely, we argue that a strong-disorder fixed point controls the low temperature susceptibility $\chi (T)$ of an exactly solvable $S=1/2$ model on the decorated honeycomb lattice with quenched bond disorder and/or vacancies, leading to $\chi (T)=\mathcal{C}/T+\mathcal{D}{T}^{\alpha (T)-1}$ where $\alpha (T)\to 0$ as $T\to 0$. The first term is a Curie tail that represents the emergent response of vacancy-induced spin textures spread over many unit cells: it is an intrinsic feature of the site-diluted system, rather than an extraneous effect arising from isolated free spins. The second term, common to both vacancy and bond disorder (with different $\alpha (T)$ in the two cases) is the response of a random singlet phase, familiar from random antiferromagnetic spin chains and the analogous regime in phosphorus-doped silicon (Si:P).

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References in corpus (9)

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• Exact deconfined gauge structures in the higher-spin Yao-Lee model: a quantum spin-orbital liquid with spin fractionalization and non-Abelian anyons
• Dilution of the magnetic lattice in the Kitaev candidate $\alpha$-RuCl${}_3$ by Rh${}^{3+}$ doping
• Frustration and chirality in three-dimensional trillium lattices: Insights and Perspectives
• Vacancies in generic Kitaev spin liquids
• Theory of collective topologically-protected Majorana fermion excitations of networks of localized Majorana modes
• Disorder, Low-Energy Excitations, and Topology in the Kitaev Spin Liquid
• Multistage spin correlations in the $s$ = 1/2 stuffed hyper-star lattice Li${}_2$Cu${}_2$(MoO${}_4$)${}_3$