Coherence Between Different Propagating Surface Plasmon Polariton Modes Excited by Quantum Mechanical Tunnel Junctions

Coherence between different surface plasmon polariton (SPP) modes excited by inelastically tunneling electrons in biased metal–insulator–metal tunnel junctions (MIM-TJs) is demonstrated. By employing a dedicated SPP stripe waveguide with MIM-TJ, an effective double-slit configuration similar to the Young's experiment realized for electrically source. The spatial correlation originates from single inelastic event and leads strong interference far-field, observed as alternate bright dark fringes Fourier plane. measured fringe-spacing inversely follows length, upper limit dictated propagation confirming mediated correlation. Finite difference time domain simulations support experimental findings. Also, simulation results unambiguously demonstrate two-step plasmonic decay process MIM-TJs. presented here provide simple robust demonstration of inherent coherence existing channels (plasmons photons) can be exploited applications tailored implications amplification quantum information processing.