Vacuum Bloch Siegert shift in Landau polaritons with ultra high cooperativity
A two level system resonantly interacting with an a.c. magnetic or electric field constitutes the physical basis of diverse phenomena and technologies. However, Schrodinger's equation for this seemingly simple system can be solved exactly only under the rotating wave approximation, which neglects the counter rotating field component. When the a.c. field is sufficiently strong, this approximation fails, leading to a resonance frequency shift known as the Bloch Siegert shift. Here, we report the vacuum Bloch Siegert shift, which is induced by the ultra strong coupling of matter with the counter rotating component of the vacuum fluctuation field in a cavity. Specifically, an ultra high mobility two dimensional electron gas inside a high Q terahertz cavity in a quantizing magnetic field revealed ultra narrow Landau polaritons, which exhibited a vacuum Bloch Siegert shift up to 40 GHz. This shift, clearly distinguishable from the photon field self interaction effect, represents a unique manifestation of a strong field phenomenon without a strong field.The Bloch Siegert shift a strong field phenomenon that implies a failure of the rotating wave approximation is observed in the polariton dispersion diagram of a two dimensional electron gas system inside a high Q terahertz photonic crystal cavity.
2018 Conference on Lasers and Electro Optics (CLEO)