Tunable and Non-Reciprocal THz Wave Manipulation in Thermally Engineered Chiral Phononic Systems

Chiral phonons are collective lattice vibrations with rotational atomic motion. Recently, chiral systems have been excited with coherent light sources to achieve magnetism and micro-degree Faraday rotation in the visible. In this talk, we demonstrate that chiral phonons can be strongly excited via asymmetric thermal gradients, implemented through Joule heating in thermally engineered devices. THz time-domain spectroscopy reveals tunable responses and large Faraday rotation exceeding 3 degrees in ultrathin-samples, associated with a giant effective magnetization. This thermally driven approach offers a new and integrated paradigm to achieve magnetism, electrical tunability, and strong non-reciprocal responses at microwave, mm-wave, and THz frequencies by simply applying a DC bias.