Observation of Ground and Excited Flat Band States in Graphene Photonic Ribbons. (arXiv:1709.07371v1 [physics.optics])

Understanding the wave transport and localisation is a major goal in the
study of lattices of different nature. In general, inhibiting the energy
transport on a perfectly periodic and disorder-free system is challenging,
however, some specific lattice geometries allow localisation due to the
presence of dispersionless (flat) bands in the energy spectrum. Here, we report
on the experimental realisation of a quasi-one-dimensional photonic graphene
ribbon supporting four flat-bands. We study the dynamics of fundamental and
dipolar modes, which are analogous to the s and p orbitals, respectively. In
the experiment, both modes (orbitals) are effectively decoupled from each
other, implying two sets of six bands, where two of them are completely flat.
Using an image generator setup, we excite the s and p flat band modes and
demonstrate their non-diffracting propagation for the first time. Our results
open an exciting route towards photonic emulation of higher orbital dynamics.

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