Open AccessA terahertz-driven non-equilibrium phase transition in a room temperature atomic vapour
Author(s) -
Christopher G. Wade,
Matteo Marcuzzi,
Emanuele Levi,
Jorge Douglas Massayuki Kondo,
Igor Lesanovsky,
Charles S. Adams,
Kevin J. Weatherill
Publication year - 2018
Publication title -
nature communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.559
H-Index - 365
ISSN - 2041-1723
DOI - 10.1038/s41467-018-05597-4
Subject(s) - terahertz radiation , electric field , terahertz spectroscopy and technology , physics , optoelectronics , phase transition , excitation , rydberg formula , detector , materials science , atomic physics , optics , condensed matter physics , ion , quantum mechanics , ionization
There are few demonstrated examples of phase transitions that may be driven directly by terahertz frequency electric fields, and those that are known require field strengths exceeding 1 MV cm −1 . Here we report a non-equilibrium phase transition driven by a weak (≪1 V cm −1 ), continuous-wave terahertz electric field. The system consists of room temperature caesium vapour under continuous optical excitation to a high-lying Rydberg state, which is resonantly coupled to a nearby level by the terahertz electric field. We use a simple model to understand the underlying physical behaviour, and we demonstrate two protocols to exploit the phase transition as a narrowband terahertz detector: the first with a fast (20 μs) non-linear response to nano-Watts of incident radiation, and the second with a linearised response and effective noise equivalent power ≤1 pW Hz −1/2 . The work opens the door to a class of terahertz devices controlled with low-field intensities and operating in a room temperature environment.