Observation of valley Landau-Zener-Bloch oscillations and pseudospin imbalance in photonic graphene

Abstract

We demonstrate inter-valley Bloch oscillation (BO) and Landau-Zener tunneling (LZT) in an optically-induced honeycomb lattice with a refractive index gradient. Unlike previously observed BO in a gapped square lattice, we show non-adiabatic beam dynamics that are highly sensitive to the direction of the index gradient and the choice of the Dirac cones. In particular, a symmetry-preserving potential leads to nearly perfect LZT and coherent BO between the inequivalent valleys, whereas a symmetry-breaking potential generates asymmetric scattering, imperfect LZT, and valley-sensitive generation of vortices mediated by a pseudospin imbalance. This clearly indicates that, near the Dirac points, the transverse gradient does not always act as a simple scalar force as commonly assumed, and the LZT probability is strongly affected by the sublattice symmetry as analyzed from an effective Landau-Zener Hamiltonian. Our results illustrate the anisotropic response of an otherwise isotropic Dirac platform to real-space potentials acting as strong driving fields, which may be useful for manipulation of pseudospin and valley degrees of freedom in graphene-like systems.

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Cited by in corpus (18)

• Topological Photonics
• Nonadiabatic Landau-Zener-Stückelberg-Majorana transitions, dynamics, and interference
• Topological Valley Hall Edge State Lasing
• Angular-dependent Klein tunneling in photonic graphene
• Valley vortex states and degeneracy lifting via photonic higher-band excitation
• Higher-order exceptional point and Landau-Zener Bloch oscillations in driven non-Hermitian photonic Lieb lattices
• Rabi-like oscillation of photonic topological valley Hall edge states
• Bloch oscillations of topological edge modes
• Complex Berry phase and imperfect non-Hermitian phase transitions
• Stable Bloch oscillations and Landau-Zener tunneling in a non-Hermitian $\mathcal{P}\mathcal{T}$-symmetric flat band lattice
• Observation of period-doubling Bloch oscillations
• Irregular Bloch Zener oscillations in two-dimensional flat-band Dirac materials
• Non-Hermitian Bloch-Zener phase transition
• Artificial gauge fields and topological insulators in Moire superlattices
• Nonadiabatic transition at a band-touching point
• Topological phenomena demonstrated in photorefractive photonic lattices
• Anomalous Topological Bloch Oscillations under Non-Abelian Gauge Fields
• Multi-tunneling effect of nonreciprocal Landau-Zener tunneling: Insights from DC field responses