Freiburg 2024 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 47: Open Quantum Systems

Q 47.8: Talk

Thursday, March 14, 2024, 12:45–13:00, HS 3219

Exceptional points at x-ray wavelengths — •Fabian Richter and Adriana Pálffy — Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

Non-Hermitian Hamiltonians allow for an effective description of dissipative systems. They exhibit a variety of exciting phenomena that cannot be observed in the Hermitian realm. Exceptional Points (EPs) are a prime example thereof. At EPs not only the complex eigenvalues, but also the eigenvectors coalesce and sensitivity to perturbations is enhanced. This concept has recently found fertile ground in optics and photonics where non-Hermitian eigenstates can be created and superposed through optical gain and loss [1]. So far, these concepts have been mostly discussed in the optical regime. Similar control of x-rays is desirable due to their superior penetration power, high focusability and detection efficiency.

Here, we investigate theoretically non-Hermitian x-ray photonics in a thin-film cavity setup containing Mössbauer nuclei resonant to the x-ray radiation entering under grazing incidence. These cavities present loss that can be controlled via adjustment of the cavity geometry and the x-ray incidence angle [2]. We show that external magnetic fields may be used to tune the system towards EPs and explore the rich topological properties of the x-ray thin-film nanostructures.

[1] L. Feng et al., Nature Photon. 11, 752-762 (2017).

[2] X. Kong, D. Chang, A. Pálffy , Phys. Rev. A 102, 033710 (2020).

Keywords: Quantum Optics; Non-Hermiticity; Cavity QED