Carbon nanotube quantum dots as highly sensitive terahertz-cooled spectrometers.

Terahertz technology has recently emerged as a highly sought-after and versatile scientific tool in many fields, including medical imaging, security screening, and wireless communication. However, scientific progress has been hindered by the lack of sources and detectors in this frequency range, thereby known as the terahertz gap. Here, we show that carbon nanotube quantum dots coupled to antennas are extremely sensitive, broad-band, terahertz quantum detectors with spectral resolution. Their response is due to photon-assisted single-electron tunneling and it is substantially enhanced by a novel radiation-induced nonequilibrium cooling of the electrons, causing a sharp height increase of the Coulomb oscillation peaks.