Abstract
Quantum spin liquids are materials that feature quantum entangled spin correlations and avoid magnetic long-range order at T = 0 K. Particularly interesting are two-dimensional honeycomb spin lattices where a plethora of exotic quantum spin liquids have been predicted. Here, we experimentally study an effective S = 1/2 Heisenberg honeycomb lattice with competing nearest and next-nearest-neighbour interactions. We demonstrate that YbBr3 avoids order down to at least T = 100 mK and features a dynamic spin–spin correlation function with broad continuum scattering typical of quantum spin liquids near a quantum critical point. The continuum in the spin spectrum is consistent with plaquette type fluctuations predicted by theory. Our study is the experimental demonstration that strong quantum fluctuations can exist on the honeycomb lattice even in the absence of Kitaev-type interactions, and opens a new perspective on quantum spin liquids.
Highlights
Magnetism arises because of the quantum mechanical nature of the electron spin, yet for the understanding of many materials, those used in today’s applications, a classical approach is sufficient
Fault-tolerant quantum computers are proposed to operate with anyon quasi-particles[2] which exist in a class of quantum spin liquids[4,5]
Quantum spin liquids (QSL) are caused by quantum fluctuations which reduce the size of the ordered magnetic moment of static magnetic structures and can affect the dynamics of the spin excitations
Summary
Magnetism arises because of the quantum mechanical nature of the electron spin, yet for the understanding of many materials, those used in today’s applications, a classical approach is sufficient. Quantum spin liquids (QSL) are caused by quantum fluctuations which reduce the size of the ordered magnetic moment of static magnetic structures and can affect the dynamics of the spin excitations. This happens in the S = 1/2 frustrated antiferromagnetic square lattice, with competing nearest and next-nearestneighbour interactions, J1, J2, where the zone boundary spinwaves develop a dispersion due to the presence of quantum dimer-type fluctuations between nearest neighbours[6]. It is expected that frustration enforces a quantum phase transition at which fractionalization of magnons into deconfined spinons occurs[16]
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