November 2018

Abstracts of the QSIT Lunch Seminar, Thursday, November 1, 2018

Axial gauge field in an acoustic Weyl metamaterial

Valerio Peri – Condensed Matter Theory and Metamaterials (Huber group), ETH Zurich

Using super-structures one can effectively change the way that sound waves propagate in space. Topological band theory, known from the description of electrons in solids, provides us with a powerful design-principle for such acoustic metamaterials. Weyl points are robust conical band crossings in three dimensional materials that are monopoles of Berry curvature. When a gauge field is applied to Weyl systems dispersing chiral channels appear along the direction parallel to the field. Here, we present the first observation of chiral Landau levels induced by an axial gauge field in a purely classical acoustic metamaterial and investigate non-local mixed bulk-boundary orbits characteristic of Weyl systems in the presence of a gauge field.

Magneto-transport ultrastongly coupled to vacuum fields

Felice Appugliese – Quantum Optoelectronics Group (Faist group), ETH Zurich

The Ultrastrong light-matter coupling regime (USC) has attracted many theoretical and experimental investigations because of its unique properties, e.g. a change in the ground state of an electronic system. One way to achieve USC is to couple inter Landau Levels transitions with planar split ring resonators operating in the microwaves [1].
Polaritons are usually accessed by their optical part; we recently developed a new experimental platform, which allows us to investigate the peculiarities of ultra strong coupling in the matter part of the polariton state, by using GaAs/AlGaAs Hall bars inside microwave cavities [2]. In such a system, the resonant photons in the cavity couple with the electrons at the Fermi level, the same that are contributing to transport.
Magneto-transport measurements, performed under weak illumination, exhibit a change in the longitudinal magnetoresistance due to the creation of mixed light-matter quasi-particles (polaritons).
We report evidences of modifications of the transport even in the dark (without external illumination and with a negligible thermal occupation of photons), due to the high vacuum Rabi splitting of the resonators.

[1] G. Scalari et al., external page Science 335, 1323 (2012)
[2] G. Paravicini-Bagliani, F. Appugliese et al., external page arXiv:1805.00846 (2018)