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Theoretical Physics

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The research in the Theoretical Physics group is primarily focused on condensed matter physics/theoretical materials science, nanoscience and electromagnetic modeling.

The group also gives a large number of courses on graduate as well as undergraduate levels.

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Highlights

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Strongly localized moving discrete dissipative breather-solitons in Kerr nonlinear media supported by intrinsic gain

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Magnus Johansson, Jaroslaw E. Prilepsky, and Stanislav A. Derevyanko

PHYSICAL REVIEW E 89 , 042912 (2014)

We investigate the mobility of nonlinear localized modes in a generalized discrete Ginzburg-Landau-type model, describing a one-dimensional waveguide array in an active Kerr medium with intrinsic, saturable gain and damping. It is shown that exponentially localized, traveling discrete dissipative breather-solitons may exist as stable attractors supported only by intrinsic properties of the medium, i.e., in the absence of any external field or symmetry-breaking perturbations. Through an interplay by the gain and damping effects, the moving soliton may overcome the Peierls-Nabarro barrier, present in the corresponding conservative system, by self-induced time-periodic oscillations of its power (norm) and energy (Hamiltonian), yielding exponential decays to zero with different rates in the forward and backward directions. In certain parameter windows, bistability appears between fast modes with small oscillations and slower, large-oscillation modes. The velocities and the oscillation periods are typically related by lattice commensurability and exhibit period-doubling bifurcations to chaotically “walking” modes under parameter variations. If the model is augmented by intersite Kerr nonlinearity, thereby reducing the Peierls-Nabarro barrier of the conservative system, the existence regime for moving solitons increases considerably, and a richer scenario appears including Hopf bifurcations to incommensurately moving solutions and phase-locking intervals. Stable moving breathers also survive in the presence of weak disorder.

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Example of a phase-locked moving dissipative lattice soliton in a model for a waveguide array in an active medium with simulateneous onsite and intersite Kerr nonlinearities. The soliton internal oscillation frequency is 2:5-locked with its velocity, so the pattern repeats itself exactly after translating 5 sites.
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Last updated:08/04/14