Title: Discovery of New Applications of Scattering Singularities in Complexnon-Hermitian Systems
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Abstract: Much of modern physics is based on the study of Hermitian quantum and classical systems in which the effects of loss or gain are either excluded or ignored. This ensures that the eigenvalues of the Hamiltonian are real and the eigenvectors are orthogonal.  However, by including interactions of the system with the environment, the Hamiltonian describing this new system is no longer Hermitian. This non-hermiticity generally renders the eigenvalues complex, and the eigenvectors are no longer orthogonal. However, non-Hermitian Hamiltonian systems offer qualitatively new phenomena and features that are not found in the Hermitian case. These include the possibility of Coherent Perfect Absorption (CPA), exceptional points (EP), and others. CPA occurs when a specific eigenvector injected into a system is completely absorbed, nothing is transmitted or reflected. EP’s are points in the parameter space of a non-Hermitian operator where its eigenvalues and associated eigenvectors coalesce and become degenerate. We can create the conditions for both CPA’s and EP’s experimentally and theoretically by perturbing a system with tunable parameters, such as frequency and the applied bias voltage on a metasurface inside the system. By parametrically varying the tunable parameters, we can controllably manipulate the locations of the CPAs and EP’s. Combining both CPA and an EP at the same point, we experimentally demonstrate a unique magnitude/phase-insensitive 50:50 In-phase/Quadrature(I/Q) power splitter.
Advisor: Steve Anlage