Gate-tunable single terahertz meta-atom ultrastrong light-matter coupling

TL;DR

This paper demonstrates electrically tunable ultrastrong light-matter coupling in a terahertz system using a gate-controlled 2D electron gas, enabling in-situ adjustment of coupling strength and observing Landau polaritons.

Contribution

It introduces the first terahertz far-field spectroscopy of an electrically tunable interaction between a single resonator and electrons in a GaAs quantum well.

Findings

Normalized coupling strength tunable from 0.46 to 0.18

Confined electrons to sub-wavelength dimensions as small as 410 nm

Observed Landau polariton dispersion dependence on electric bias

Abstract

We study the electrical tunability of ultrastrong light-matter interactions between a single terahertz circuit-based complementary split ring resonator (cSRR) and a two-dimensional electron gas. For this purpose, transmission spectroscopy measurements are performed under the influence of a strong magnetic field at different set points for the electric gate bias. The resulting Landau polariton dispersion depends on the applied electric bias, as the gating technique confines the electrons in-plane down to extremely sub-wavelength dimensions as small as d = 410 nm. This confinement allows for the excitation of standing plasma waves at zero magnetic field and an effective tunability of the electron number coupled to the THz resonator. This allows the normalized coupling strength to be tuned in-situ from $\eta$ = 0.46 down to $\eta$ = 0.18. This is the first demonstration of terahertz far-field spectroscopy of an electrically tunable interaction between a single terahertz resonator and electrons in a GaAs quantum well heterostructure.