Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dipolar spin ice states with fast monopole hopping rate in CdEr$_2$X$_4$
  (X = Se, S)   Excitations in a spin ice behave as magnetic monopoles, and their population
and mobility control the dynamics of a spin ice at low temperature.
CdEr$_2$Se$_4$ is reported to have the Pauling entropy characteristic of a spin
ice, but its dynamics are three-orders of magnitude faster than the canonical
spin ice Dy$_2$Ti$_2$O$_7$. In this letter we use diffuse neutron scattering to
show that both CdEr$_2$Se$_4$ and CdEr$_2$S$_4$ support a dipolar spin ice
state -- the host phase for a Coulomb gas of emergent magnetic monopoles. These
Coulomb gases have similar parameters to that in Dy$_2$Ti$_2$O$_7$, i.e. dilute
and uncorrelated, so cannot provide three-orders faster dynamics through a
larger monopole population alone. We investigate the monopole dynamics using ac
susceptometry and neutron spin echo spectroscopy, and verify the crystal
electric field Hamiltonian of the Er$^{3+}$ ions using inelastic neutron
scattering. A quantitative calculation of the monopole hopping rate using our
Coulomb gas and crystal electric field parameters shows that the fast dynamics
in CdEr$_2$X$_4$ (X = Se, S) are primarily due to much faster monopole hopping.
Our work suggests that CdEr$_2$X$_4$ offer the possibility to study alternative
spin ice ground states and dynamics, with equilibration possible at much lower
temperatures than the rare earth pyrochlore examples.

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The categories of this paper are: funct-an
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The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: physics
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The categories of this paper are: atom-ph
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The categories of this paper are: adap-org
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The categories of this paper are: math-ph
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The categories of this paper are: cs
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The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg