Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A gap-protected zero-Hall effect state in the quantum limit of the
  nonsymmorphic metal KHgSb   A recurring theme in topological matter is the protection of unusual
electronic states by symmetry, for example, protection of the surface states in
Z2 topological insulators by time reversal symmetry [1-3]. Recently interest
has turned to unusual surface states in the large class of nonsymmorphic
materials [4-11]. In particular KHgSb is predicted to exhibit double quantum
spin Hall (QSH) states [10]. Here we report observation of a novel feature of
the Hall conductivity in KHgSb in strong magnetic field B. In the quantum
limit, the Hall conductivity is observed to fall exponentially to zero, but the
diagonal conductivity is finite. A large gap protects this unusual zero-Hall
state. We propose that, in this limit, the chemical potential drops into the
bulk gap, intersecting equal numbers of right and left-moving QSH surface modes
to produce the zero-Hall state.

5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
16
The categories of this paper are: stat
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The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
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The categories of this paper are: eess
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The categories of this paper are: econ