Effect of quantized conductivity on the anomalous photon emission radiated from atomic-size point contacts

Abstract

We observe anomalous visible to near-infrared electromagnetic emission from electrically driven atomic-size point contacts. We show that the number of photons released strongly depends on the quantized conductance steps of the contact. Counterintuitively, the light intensity features an exponential decay dependence with the injected electrical power. We propose an analytical model for the light emission considering an out-of-equilibrium electron distribution. We treat photon emission as a Bremsstrahlung process resulting from hot electrons colliding with the metal boundary, and find qualitative accord with the experimental data.

Too Cool for Blackbody Radiation: Overbias Photon Emission in Ambient STM Due to Multielectron Processes

“…Electroluminescence in tunnel junctions was first observed by Lambe and McCarthy in 1976. , More recently, light emission with photon energies exceeding the energy of tunneling electrons, so-called overbias emission, was observed, prompting a series of experimental and theoretical papers to explain the phenomena . The candidate explanations include the shape of the Fermi distribution at elevated electron temperatures, , multielectron processes, − and blackbody radiation. − Multielectron processes are particularly interesting from a technological standpoint because they offer a route to nanoscale electro-optical transducers with low operating voltage and broadband emission spectra . However, photon emission from multielectron processes has only been demonstrated at low temperatures, − which limits its use in devices, and studies at room temperature have attributed overbias emission to blackbody radiation or the shape of the Fermi distribution. ,− …”

“…The candidate explanations include the shape of the Fermi distribution at elevated electron temperatures, , multielectron processes, − and blackbody radiation. − Multielectron processes are particularly interesting from a technological standpoint because they offer a route to nanoscale electro-optical transducers with low operating voltage and broadband emission spectra . However, photon emission from multielectron processes has only been demonstrated at low temperatures, − which limits its use in devices, and studies at room temperature have attributed overbias emission to blackbody radiation or the shape of the Fermi distribution. ,− …”

Atomic-Scale Structural Fluctuations of a Plasmonic Cavity

“…Overbias emission occurs when the energy of the emitted photons exceeds the potential difference U seen by the transmitted electrons, h > eU [43][44][45][46][47]. The underlying mechanism is strongly debated in the literature and has either been assigned to plasmon-mediated coherent interaction between electrons [46,[48][49][50] or photon emission from a hot electron gas [45,47,51].…”

“… 47 − 53 The underlying mechanism is strongly debated in the literature and has either been assigned to plasmon-mediated coherent interaction between electrons 50 , 54 − 56 or photon emission from a hot electron gas. 49 , 51 , 57 …”

“…To reduce heat dissipation at high currents in our experiment, we apply a rather low voltage (on the order of 1 V) and operate the junction in an overbias light emission regime that leads to geometrically more stable junctions that undergo changes only on a time scale of seconds and remain intact over extended measurement times. Overbias emission occurs when the energy of the emitted photons exceeds the potential difference U seen by the transmitted electrons, h ν > eU . − The underlying mechanism is strongly debated in the literature and has either been assigned to plasmon-mediated coherent interaction between electrons ,− or photon emission from a hot electron gas. ,, …”