Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Zero-index and Topology in 1D Phononic Metamaterials with Negative Mass
  and Negative Coupling   Phononic metamaterials have attracted extensive attention since they are
exibly adjustable to control the phonon transmission. In this work, we study a
one-dimensional phononic metamaterial, made of mechanical resonant oscillators
and chiral couplings. We show that by design, the oscillator mass and
inter-oscillator coupling, although both are positive naturally, can be either
single negative or double negative effectively within a certain frequency
range. At the frequency where the effective mass and coupling are both
infinite, a flat band emerges that will induce an extremely high density of
states. At the critical point of band degeneracy, a Dirac-like point emerges
where both effective mass and the inverse of effective coupling are
simultaneously zero, so that zero index is realized for phonons. Moreover, the
phononic topological phase transition is observed that the phononic band gap
switches between single mass-negative and single coupling-negative regime. As a
consequence, a topological interface state is identified, well explained by the
theory.

30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
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The categories of this paper are: adap-org
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: econ
6
The categories of this paper are: astro-ph