Is YbMgGaO_4 a spin liquid or a disorder-driven state? · revision history

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Title

Is YbMgGaO4 a spin liquid or a disorder-driven state?

Plain

YbMgGaO4 is a triangular-lattice magnet with no detected order and a broad continuum of spin excitations, first read as a spin-liquid signature. Its magnesium and gallium atoms are randomly mixed, which makes the couplings random, and that alone may produce the same data.

Precise

In YbMgGaO4 (effective $S = 1/2$ Yb3+ doublets on a triangular lattice, nearest-neighbor exchange of order 0.1 meV, random Mg/Ga site mixing), determine whether the $T \to 0$ ground state is a quantum spin liquid with fractionalized spinons, a random-singlet (valence-bond glass) state, or a spin glass. An answer names the state with evidence that discriminates the three: the field and temperature scaling of $C$ and $\chi$, ac-susceptibility freezing below 0.1 K, and whether the neutron continuum is reproduced by a disordered model without fractionalization.

Settled by

Neutron spectra, ac susceptibility below 0.1 K and thermal conductivity on the same crystals, compared quantitatively with simulations of the fitted anisotropic exchange model that include the measured distribution of random couplings.

Kind

phenomenon

Answer type

classification

References

(empty)

Literature status

contested

Status note

Zhu et al. (PRL 2017) reproduced the continuum by bond disorder acting on a model whose clean ground state is stripe ordered, Kimchi et al. (PRX 2018) proposed a random-singlet state, and Ma et al. (PRL 2018) found spin-glass freezing in the sister compound YbZnGaO4.

Posed since

2015