Wilson-Rae, Ignacio

Date: Friday April 4, 2014
Time: 13:00
Place: ETH Zurich, Hönggerberg, HIT J 53
Host: Atac Imamoglu

Carbon-nanotube optomechanics

Ignacio Wilson-Rae
University of York, U.K.

Carbon nanotubes (CNTs) constitute a promising system for quantum optomechanics. Here we propose two optomechanical schemes for demonstrating quantum effects in the motion of a suspended CNT subjected to an inhomogeneous electric field. The first one is based on deformation-potential exciton-phonon coupling. In this case the electric field generates an optically active quantum dot featuring a tunable parametric coupling between the confined excitons and the flexural phonons of the nanotube. For a small suspended length, this interaction enables efficient optical ground-state cooling of the fundamental mode and allows to realise a mechanical analogue of cavity-QED. In turn, in the limit of large suspended length, this system exhibits a collapse of the excitonic zero-phonon line that can be ascribed to the "localised" phase of a subohmic spin-boson model, and is associated to Non-Markovian dephasing leading to sideband spectra characterised by half-integer power-law decays. The second optomechanical scheme exploits geometric nonlinearity and a softening instability of the fundamental mode induced by the electric field. Tuning "below" the instability enhances the zero-point motion leading to a sizeable geometric nonlinearity per quanta. This allows to demonstrate the quantum fine structure of a "weakly anharmonic" mode and enables cavity-optomechanical setups where a classical optical input can induce a nonclassical motional steady-state of the CNT approaching a Fock state.