Tunneling time probed by quantum shot noise

Abstract

In typical metallic tunnel junctions, the tunneling events occur on a femtosecond timescale. An estimation of this time requires current measurements at optical frequencies and remains challenging. However, it has been known for more than 40 years that as soon as the bias voltage exceeds one volt, the junction emits infrared radiation as an electrically driven optical antenna. We demonstrate here that the photon emission results from the fluctuations of the current inside the tunneling barrier. Photon detection is then equivalent to a measurement of the current fluctuations at optical frequencies, allowing to probe the tunneling time. Based on this idea, we perform optical spectroscopy and electronic current fluctuation measurements in the far from equilibrium regime. Our experimental data are in very good agreement with theoretical predictions based on the Landauer Büttiker scattering formalism. By combining the optics and the electronics, we directly estimate the so-called traversal time.

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

“…This was experimentally measured on tunnel junctions at cryogenic temperature and emitting in the gigahertz (GHz) frequency range [15,16]. For larger driving biases, the situation becomes complicated and the standard fluctuation-dissipation theory is no longer applicable [17,18]. Electron-electron scattering must be included in the dissipation, as it contributes to the elevatation of the temperature of the Fermi-Dirac distribution.…”

Out‐of‐Equilibrium Fluctuation‐Dissipation Relations Verified by the Electrical and Thermoelectrical AC‐Conductances in a Quantum Dot

“…Note that the noise depends on the reservoir indexes when the following conditions are all filled: non‐zero frequency, energy dependent transmission coefficient and asymmetry of the potential profile across the system . It was confirmed by two recent experiments on carbon nanotube quantum dot and on tunnel junction …”

Optical antennas driven by quantum tunneling: a key issues review

“…On the other hand, the IET process constitutes an electronic drive for optical modes. It is thought to be ultrafast as the ultimate limiting time-scale of mode excitation is given by the electron tunneling time, a femtosecond scale process [73][74][75]. Moreover, a tunnel junction is arguably the smallest possible light source.…”

“…As the transfer Hamiltonian model [114][115][116][117][118][119] is of a perturbative nature its applicability is restricted to strong tunnel barriers where the interaction between the two electrodes is weak. In the high conductivity regime the current fluctuations model [46,75,99,[104][105][106][107][108][109][110][111][112][113] has proven to accurately describe experimental results. While in most works a single theoretical approach is chosen, it has been shown that the theories of spontaneous emission and finite frequency shot noise are closely related [120].…”

“…Recently, Fevrier and Gabelli used measurements of the light emission from MIM tunneling devices as a probe for the tunneling time [75]. In conjunction with a current fluctuations model based on the Landauer-Büttiker scattering formalism, tunneling times of the order of one femtosecond were inferred.…”