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Register a new userFinite frequency noise of a superconductor/ferromagnet quantum point contact
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We have calculated the finite-frequency current noise of a superconductor-ferromagnet quantum point contact (SF QPC). This signal is qualitatively affected by the spin-dependence of interfacial phase shifts (SDIPS) acquired by electrons upon reflection on the QPC. For a weakly transparent QPC, noise steps appear at frequencies or voltages determined directly by the SDIPS. These steps can occur at experimentally accessible temperatures and frequencies. Finite frequency noise is thus a promising tool to characterize the scattering properties of a SF QPC.
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Nanostructured superconductor/ferromagnet heterocontacts are studied in the different transport regimes of point-contact spectroscopy. Direct measurements of the nanocontact size by scanning electron microscopy allow a comparison with theoretical models for contact-size estimates of heterocontacts. Our experimental data give evidence that size estimates yield reasonable values for the point-contact diameter $d$ as long as the samples are carefully characterized with respect to the local electronic parameters.
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We report on direct measurements of the electronic shot noise of a quantum point contact at frequencies nu in the range 4-8 GHz. The very small energy scale used ensures energy independent transmissions of the few transmitted electronic modes and their accurate knowledge. Both the thermal energy and the quantum point contact drain-source voltage Vds are comparable to the photon energy hnu leading to observation of the shot noise suppression when $V_{ds}<h u/e$. Our measurements provide the first complete test of the finite frequency shot noise scattering theory without adjustable parameters.
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