We study quantum effects in nanoelectronic systems at very low temperatures, probed both by Scanning Probe and Transport techniques. Present and recent research topics include:
Although renown for its extraordinary properties, graphene exhibits spatial doping disorder, the so-called electron-hole puddles. These local charge inhomogeneities show up particularly prominently for properties appearing at the Dirac point because they limit how close this point can actually be approached in a macroscopic sample. We are able to map the local doping level in graphene using scanning tunneling microscopy and spectroscopy (STM/STS).
We study thermal and thermoelectric effects in small devices, including Josephson junctions, single-electron transistors, and quantum dot junctions.
For example, the local temperature in a Josephson junction biased near its threshold of the transition to the dissipative state can already show signs of overheating, in particular when driven with a microwave field. We further investigate how to avoid this overheating and keep Josephson junctions non-hysteretic, which is important for applications in magnetometry.
We also study the ability of small devices to conduct heat. In most systems, heat and charge transport are interlinked by the Wiedemann-Franz law. Yet, we have shown for instance that in a single-electron transistor, this relation is violated, due to electron-electron interactions. Presently, we investigate principally the role of quantum correlations in the thermoelectric effects properties of single quantum dots junctions.
Superconductors (S) and quantum dots (Q) both have highly non-trivial electronic properties. Combining both in a SQS junction allows to study a wealth of phenomena. If driven with an ac gate signal, such a device can be tuned to deliver exactly one electron per gate cycle. This has important applications in metrology and quantum coherent single electronics.
