### Séminaire de groupe

Les effets de “charge-vibration” dans des systèmes mésoscopiques |

Gianluca Rastelli |

Konstanz |

vendredi 06 avril 2018 , 10h25 |

Salle de séminaire du groupe de Physique Statistique |

Mesoscopic conductors coupled to localised, quantum harmonic resonators have now become a commonly studied system, both experimentally and theoretically. One of the most interesting phenomena in such systems is the interplay between the resonator dynamics and the quantum transport, at the level of single electron. Studying them can help us gain important insights into fundamental issues of quantum mechanics. Furthermore, such systems typically operate far from equilibrium and can be very strongly nonlinear, allowing us to unveil quantum dynamical properties unexplored in the past. For example, electro-mechanical systems pave the way for observing quantum effects in large mechanical systems containing many billions individual atoms. To achieve such a goal, a crucial requirement is cooling the mechanical resonator, integrated in an electrical circuit, to very low temperature. I will present theoretical proposals for controlling the nonequilibrium steady state of nanomechanical resonators integrating quantum dots. One of the main results is that ground state cooling of the resonator can be realistically achieved using spin-polarised current [1,2] or superconducting contacts [3,4]. In the last part, I will discuss recent results obtained in a nanomechanical system encoding a single atom (phonon) lasing. In this case, the mechanical resonator plays the role of the cavity, which is characterised by a rich phase diagram associated to multistability regions [5]. For different proposals and various regimes, I will discuss how such non-equilibrium states of the resonator can be readily detected by simple measurements of the dc current. [1] P. Stadler, W. Belzig, G. Rastelli, âGround-state cooling of a carbon nanomechanical resonator by spin-polarized currentâ, Phys. Rev. Lett. 113, 047201 (2014). [2] P. Stadler, W. Belzig, G. Rastelli, âControl of vibrational states by spin-polarized transport in a carbon nanotube resonatorâ, Phys. Rev. B 91, 085432 (2015). [3] P. Stadler, W. Belzig, G. Rastelli, "Ground-State Cooling of a Mechanical Oscillator by Interference in Andreev Reflectionâ, Phys. Rev. Lett. 117, 197202 (2016). [4] P. Stadler, W. Belzig, G. Rastelli, âCharge-vibration interaction effects in normal-superconductor quantum dotsâ, Phys. Rev. B. 96 , 045429 (2017). [5] M. Mantovani, A. Armour, W. Belzig, G. Rastelli, âMultistability in a nanomechanical single atom laserâ (to be submitted). |