Jiandong Chen, Chubin Lin, Peng Zhang, John Verboncoeur, L. K. Ang, Yangyang Fu
This Letter reports the simultaneous excitation of two terahertz plasma waves in field-emission-driven microdischarges. As demonstrated by first-principle particle-in-cell simulations, we reveal that one wave results from intermittent field emission due to space-charge effects, while the other arises from a two-stream instability between cathode field-emission electrons and anode multipactor electrons, which can trap less energetic electrons, leading to circumnutation trajectories and increased collisionality. A dispersion relation is derived from fluid equations, showing good agreement with the simulated wave parameters. The findings of this Letter provide a foundation and potential pathway for designing novel terahertz sources at miniaturized scales.