Valence Bonds in Random Quantum Magnets: Theory and Application to YbMgGaO4
By I. Kimchi, A. Nahum, T. Senthil. Physical Review X, 2017
213 citations recorded by the source corpus.
We analyze the effect of quenched disorder on spin-1/2 quantum magnets in which magnetic frustration promotes the formation of local singlets. Our results include a theory for 2D valence-bond solids subject to weak bond randomness, as well as extensions to stronger disorder regimes where we make connections with quantum spin liquids. We find, on various lattices, that the destruction of a valence-bond solid phase by weak quenched disorder leads inevitably to the nucleation of topological defects carrying spin-1/2 moments. This renormalizes the lattice into a strongly random spin network with interesting low-energy excitations. Similarly, when short-ranged valence bonds would be pinned by stronger disorder, we find that this putative glass is unstable to defects that carry spin-1/2 magnetic moments, and whose residual interactions decide the ultimate low-energy fate. Motivated by these results we conjecture Lieb-Schultz-Mattis-like restrictions on ground states for disordered magnets with spin 1/2 per statistical unit cell. These conjectures are supported by an argument for 1D spin chains. We apply insights from this study to the phenomenology of YbMgGaO4, a recently discovered triangular lattice spin-1/2 insulator which was proposed to be a quantum spin liquid. We instead explore a description based on the present theory. Experimental signatures, including unusual specific heat, thermal conductivity, and dynamical structure factor, and their behavior in a magnetic field, are predicted from the theory, and compare favorably with existing measurements on YbMgGaO4 and related materials.
Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics
View Paper: https://www.semanticscholar.org/paper/fd5c3f02a0349b77610b09988f6728dff28d5549
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In Atomic and Molecular Physics, and Optics
In Condensed Matter Physics
Citations in the corpus
- Average Symmetry-Protected Topological Phases (2022, background): “The average symmetry (or statistical symmetry)[9, 13, 14, 23] G only commutes with H0 and is broken by each realization of the disorder potential, so effectively the disorder potential v transforms non-trivially under G.”