NER: Quantum Nanosensors Based on Controllable Electron-Phonon Coupling

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This proposal was received in response to NSE, NSF-0019. Sensitivity at the level of individual quanta is required for such diverse applications of nanosensors as characterization of macromolecules and biological objects, monitoring of molecular binding, and control of dephasing processes in quantum dots. In nanoscale structures the phonon exchange is too fast, and strong thermal (phonon) coupling between the sensor and its surroundings puts strict limitations on the sensitivity of ordinary bolometric sensors. In the hot-electron sensor, the incoming quanta overheat only electron states, which relax to equilibrium due to electron-phonon coupling. The sensitivity of hot-electron sensors can be improved by weakening the effective coupling between electrons and phonons. In nanoconductors, the electron-phonon interaction is substantially modified in comparison with the interaction in bulk materials. Due to the interference between electron-phonon and electron-boundary scattering, the electron relaxation/dephasing rate depends drastically on vibrations of boundaries. It may vary over a wide range, spanning several orders of magnitude, and may be controlled by selection of a substrate material. The proposed research includes complex investigations of the interference between electron scattering mechanisms in superconducting nanostructures and experimental demonstration of the electron energy relaxation controlled by elastic electron scattering from boundaries and defects as well as the design of a new hot-electron sensor with a record value of the noise equivalent power, NEP=10-20W/Hz1/2, and the energy resolution of 5 10-24J, which will be able to count individual low-energy quanta (photons or phonons).