Abstract
We demonstrate manipulation of photon emission efficiency in a tunneling gap by tuning the rates of elastic and inelastic electron tunneling processes with local electronic states. The artificial local electronic states are created by a scanning tunneling microscope tip on a CuN nanoisland grown on a Cu(100) surface at cryogenic temperature. These local electronic states can either enhance or suppress the excitation of tip-induced surface plasmon modes at specific bias voltages, and thus the induced photon emission rates. A theoretical model quantitatively analyzing inelastic and elastic tunneling processes associated with characteristic electronic states shows good agreement with experiments. We also show that tip-induced photon emission measurement can be used for probing the electronic states in the tunneling gap.
Highlights
Plasmon coupled nanostructures have opened the door for emerging nanophotonics
While the dominant portion of the tunneling current arises from elastic tunneling (ET) channels, the plasmon modes and associated photon emission are mainly excited by inelastic tunneling (IET) channels [18, 19]
Under a positive bias voltage, the tip induced plasmon (TIP) photon emission efficiency can be enhanced or suppressed as large as two orders of magnitude by manipulating the local electronic states associated with these nanostructures
Summary
Plasmon coupled nanostructures have opened the door for emerging nanophotonics. As the gap between the metal nanostructures is reduced down to the subnanometer scale, coherent quantum tunneling of electrons dominates the plasmon modes and establishes a quantum limit for plasmonic confinement [1,2,3,4]. A general mechanism is the so-called tip induced plasmon (TIP), in which local plasmon modes are excited by tunneling electrons [5, 12,13,14,15,16,17]. We report on a study of using artificially-created local electronic states to enhance or suppress the efficiency of TIP photon emission. This has been achieved through altering the ratio of IET to ET in the tunneling process with local electronic states. Under a positive bias voltage, the TIP photon emission efficiency can be enhanced or suppressed as large as two orders of magnitude by manipulating the local electronic states associated with these nanostructures. Our findings may lead to applications in designing and engineering nanophotonic devices at the quantum tunneling regime
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