Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Topological Invariants of a Filling-Enforced Quantum Band Insulator   Traditional ionic/covalent compound insulators arise from a commensuration
between electron count and system volume. On the other hand, conventional
topological insulators, outside of quantum hall effect systems, do not
typically display such a commensuration. Tnstead, they can undergo a phase
transition to a trivial insulator that preserves the electron filling.
Nevertheless, in some crystalline insulators, termed filling-enforced quantum
band insulators (feQBIs), electron filling can dictate nontrivial topology in
the insulating ground state. Currently, little is known about the relation
between feQBIs and conventional topological invariants. In this work, we study
such relations for a particularly interesting example of a half-filling feQBI
that is realized in space group 106 with spinless electrons. We prove that any
4-band feQBI in space group 106 with filling 2 must have a nontrivial
topological invariant, namely the $\mathbb{Z}_2$ glide invariant, and thus must
have a quantized magnetoelectric polarizability $\theta=\pi$. We thus have
found a three-dimensional example where electron filling and band topology are
tied. Such a locking raises intriguing questions about the generality of the
band-inversion paradigm in describing the transition between trivial and
topological phases.

30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
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The categories of this paper are: eess
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
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The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs