QDev Seminar: Frederico Martins

Imaging and manipulating quantum transport at the nanometer scale
In the last thirty years, progresses in nanofabrication techniques have allowed to explore electron transport inside extremely small and ‘clean’ devices. Confined in such nano-devices electrons often reveal their true complex nature, and a rich spectrum of new phenomena emerges, with signatures of energy quantification, charge discreteness, and/or electron interferences and interactions.

Characterization tools followed a similar downsizing trend, concomitant with the evolution of nanodevice fabrication. In particular, the Atomic Force Microscope (AFM) and Scanning Tunneling Microscope (STM) democratized nanoprobing ‘down to the atomic scale’.

In this presentation, I will give a few examples illustrating how an AFM-derived technique (namely the "scanning gate microscopy") can give access to real-space visualization of electron transport phenomena in archetypal mesoscopic devices such as quantum rings [1] or quantum point contacts [2]. I will show that, imaging the electron behavior at the nanometer scale, one can even decrypt complex quantum transport phenomena, such as tunneling between quantum Hall edge states in mesoscopic devices [3], in a very direct way. This technique opens, therefore, the door towards a more “intimate” manipulation of charge and quasiparticle transport.

[1] B. Hackens et al., Nature Phys. 2, 826 (2006); F. Martins et al., Phys. Rev. Lett. 99, 136807 (2007); M. G. Pala et al., Phys. Rev. B 77, 125310 (2008).

[2] M. Topinka et al., Nature 410, 183 (2001); B. Brun et al. arxiv.org/abs/1307.8328

[3] B. Hackens et al., Nature Comm. 1, 39 (2010); F. Martins et al., Sci. Rep. 3, 1416 (2013); F. Martins et al., New J. of Phys. 15, 013049 (2013).