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We report on the observation of the giant photoconductance of a quantum point contact (QPC) in tunneling regime excited by terahertz radiation. Studied QPCs are formed in a GaAs/AlGaAs heterostructure with a high-electron-mobility two-dimensional electron gas. We demonstrate that irradiation of strongly negatively biased QPCs by laser radiation with frequency f = 0.69 THz and intensity 50 mW/cm^2 results in two orders of magnitude enhancement of the QPC conductance. The effect has a superlinear intensity dependence and increases with the dark conductivity decrease. It is also characterized by strong polarization and frequency dependencies. We demonstrate that all experimental findings can be well explained by the photon-mediated tunneling through the QPC. Corresponding calculations are in a good agreement with the experiment.
A highly superlinear in radiation intensity photoconductance induced by terahertz laser radiation with moderate intensities has been observed in quantum point contacts made of GaAs quantum wells operating in the deep tunneling regime. For very low va
A counter-intuitive disappearance of the giant terahertz photoconductance of a quantum point contact (QPC) under increase in the photon energy, which was discovered experimentally (Otteneder et al., Phys. Rev. Applied 10 (2018) 014015) and studied by
We present results for a multichannel tunneling model that describes point-contact spectra between a metallic tip and a superconducting heavy-fermion system. We calculate tunneling spectra both in the normal and superconducting state. In point-contac
We present an experimental and theoretical study of the conductance and stability of Mg atomic-sized contacts. Using Mechanically Controllable Break Junctions (MCBJ), we have observed that the room temperature conductance histograms exhibit a series
We investigate the transport properties of a superconducting quantum point contact in the presence of an arbitrary periodic drive. In particular, we calculate the dc current and noise in the tunnel limit, obtaining general expressions in terms of pho