Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pressure Tuned Insulator to Metal Transition in Eu$_2$Ir$_2$O$_7$   We have studied the effect of pressure on the pyrochlore iridate
Eu$_2$Ir$_2$O$_7$, which at ambient pressure has a thermally driven insulator
to metal transition at $T_{MI}\sim120$\,K. As a function of pressure the
insulating gap closes, apparently continuously, near $P \sim 6$\,GPa. However,
rather than $T_{MI}$ going to zero as expected, the insulating ground state
crosses over to a metallic state with a negative temperature coefficient of
resistivity, calling into question the true nature of both ground states. The
high temperature state also crosses over near 6 GPa, from an incoherent to a
conventional metal, suggesting a connection between the high and the low
temperature states.

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The categories of this paper are: quant-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: cs
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The categories of this paper are: eess
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The categories of this paper are: hep-ex
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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: nlin
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The categories of this paper are: chem-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-th