Electro-Mechanical Transition in Quantum dots

TL;DR

This paper investigates the electro-mechanical transition in quantum dots coupled to nano-mechanical oscillators, analyzing how electronic transport properties relate to mechanical signatures and their robustness under various conditions.

Contribution

It provides a detailed analysis of the relation between electronic signals and mechanical properties during the transition, including effects of temperature, bias, and dissipation.

Findings

Relation between current noise and displacement spectrum established

Gate-voltage dependence of spectra at transition characterized

Transition remains robust under external fluctuations and dissipation

Abstract

The strong coupling between electronic transport in a single-level quantum dot and a capacitively coupled nano-mechanical oscillator may lead to a transition towards a mechanically-bistable and blocked-current state. Its observation is at reach in carbon-nanotube state-of-art experiments. In a recent publication [Phys. Rev. Lett. 115, 206802 (2015)] we have shown that this transition is characterized by pronounced signatures on the oscillator mechanical properties: the susceptibility, the displacement fluctuation spectrum and the ring-down time. These properties are extracted from transport measurements, however the relation between the mechanical quantities and the electronic signal is not always straightforward. Moreover the dependence of the same quantities on temperature, bias or gate voltage, and external dissipation has not been studied. The purpose of this paper is to fill this gap and provide a detailed description of the transition. Specifically we find: (i) The relation between the current-noise and the displacement spectrum. (ii) The peculiar behavior of the gate-voltage dependence of these spectra at the transition. (iii) The robustness of the transition towards the effect of external fluctuations and dissipation.