Quantized charge pumping and magnetic side gating in InAs nanowires

A. Baumgartner, S. d'Hollosy, G. Fábián, M. Jung, M.H. Madsen, J. Nygård and C. Schönenberger

Institute of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
Center for Quantum Devices and Nano-Science Center, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark


Semiconducting nanowires (NWs) are a versatile, highly tunable material platform at the heart of many new developments in nanoscale and quantum physics. Here report results of two separate topics: first, we demonstrate quantized charge pumping, i.e., the controlled transport of individual electrons through an InAs NW quantum dot (QD) device at frequencies up to 1.3 GHz. The QD is induced and modulated electrostatically by a series of bottom gates and a backgate. We investigate non-equilibrium effects at higher frequencies and how the dc bias, the modulation amplitude and the gate voltages can be used to control the number of charges conveyed per cycle, and discuss a simple electrostatic model that accounts for most observed effects. In a second part we report the fabrication and first magneto-resistance (MR) experiments on NW QDs equipped with ferromagnetic side gates (FSGs) with tunable switching fields, which can also be used as local electrical gates. Depending on the QD gating, we find several different MR effects, where the amplitude, resonance energy and broadening are modified by the local magnetic field. While FSGs might become useful for spin manipulation  and read-out experiments and possibly also for the creation of novel electronic states like fractional Fermions, charge pumping in InAs NWs is relevant in metrology as a current standard and opens up the opportunity to investigate exotic states of matter expected in NWs, e.g. Majorana modes or fractional Fermions, by single electron spectroscopy and correlation experiments.