Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mott insulator phases and first-order melting in BSCCO crystals with
  periodic surface holes   We measured the effects of periodic surface holes, created using a focused
ion beam, on the phase diagram of the vortex matter in high-T_c
Bi_2Sr_2CaCu_2O_{8+\delta} crystals. Differential magneto-optical measurements
show that the irreversibility line is shifted to higher fields and
temperatures, with respect to the pristine melting line. The irreversibility
line displays weak field dependence between integer matching fields indicating
multiple-flux-quanta pinning at holes. We find reduced equilibrium
compressibility of the vortex matter at integer matching fields, which is
strong evidence for the existence of thermodynamic Mott insulator phases.
Shaking with a transverse ac field surprisingly reveals first-order melting
that is not shifted with respect to the pristine melting line and that seems to
occur within the Mott insulator regions. This melting is understood to be the
first-order transition in the bulk of the crystal beneath the surface holes.
The transition is visible at the surface, despite the reduced vortex
compressibility in the top layer.

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The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org