Bipolaronic blockade effect in quantum dots with negative charging energy

¹ Center for Interdisciplinary Studies, School of Physics, Lanzhou University - Lanzhou 730000, China
² Institute of Physics, Chinese Academy of Sciences - Beijing 10080, China
³ International Center for Quantum Materials, School of Physics, Peking University - Beijing 100871, China
⁴ Collaborative Innovation Center of Quantum Matter - Beijing, China

^(a) sunqf@pku.edu.cn

Received: 9 November 2013
Accepted: 10 February 2014

Abstract

We investigate single-electron transport through quantum dots with negative charging energy induced by a polaronic energy shift. For weak dot-lead tunnel couplings, we demonstrate a bipolaronic blockade effect at low biases which suppresses the oscillating linear conductance, while the conductance resonances under large biases are enhanced. A novel conductance plateau develops when the coupling asymmetry is introduced, with its height and width tuned by the coupling strength and external magnetic field. It is further shown that the amplitude ratio of the magnetic-split conductance peaks changes from 3 to 1 for increasing coupling asymmetry. Though we demonstrate all these transport phenomena in the low-order single-electron tunneling regime, they are already strikingly different from the usual Coulomb blockade physics and are easy to observe experimentally.