Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence of the Berezinskii-Kosterlitz-Thouless Phase in a Frustrated
  Magnet   The Berezinskii-Kosterlitz-Thouless (BKT) mechanism, building upon
proliferation of topological defects in 2D systems, is the first example of
phase transition beyond the Landau-Ginzburg paradigm of symmetry breaking. Such
a topological phase transition has long been sought yet undiscovered directly
in magnetic materials. Here, we pin down two transitions that bound a BKT phase
in an ideal 2D frustrated magnet TmMgGaO$_4$, via nuclear magnetic resonance
under in-plane magnetic fields, which do not disturb the low-energy electronic
states and allow BKT fluctuations to be detected sensitively. Moreover, by
applying out-of-plane fields, we find a critical scaling behaviour of the
magnetic susceptibility expected for the BKT transition. The experimental
findings can be explained by quantum Monte Carlo simulations applied on an
accurate triangular-lattice Ising model of the compound which hosts a BKT
phase. These results provide a concrete example for the BKT phase and offer an
ideal platform for future investigations on the BKT physics in magnetic
materials.

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The categories of this paper are: math
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org