Postdoc position in Superconductivity and topological states in twisted bilayer graphene

The first measurements of superconductivity and correlated phases in twisted bilayer graphene (tBLG) brought a lot of attention to this new way to control the properties of matter: twisting layers in a van der Waals (vdW) heterostructure. The superconducting state in tBLG or twisted van der Waals structures is believed to have its origin in the interplay between the moiré superlattice and the interlayer interactions, which leads to the formation of a flat band in the electronic band structure. Controlling the twist angle between the layers allows playing with both of these parameters at the same time. As layers get more aligned, the moiré superlattice wavelength and the layer hybridization increases. However, as the two layers get more and more aligned, at angles >1.1°, the superconducting temperature decreases. A remarkable change of the critical superconducting temperature from 1.7 K to 0.5 K was reported for angular variations of 1.05 and 1.16 degrees in the case of tBLG [Cao et al., Nature 2018]. Given this astonishing result, we might wonder what is so special in the so-called magic-angle, 1.1 degrees and if other magic angles can be found where flat bands can be observed.  Up to now it seems that twisted bilayer graphene is the ideal playground for most of the condensed matter phenomena, from superconductivity to anomalous quantum Hall effect and other correlated phases. However, the most challenging part of this research seems to lay in a reliable fabrication of homogeneous samples. In our laboratory we have developed a new technique to continiously control the angular alignment between layers [Science 361, 690].

During this postdoctoral appointment, we propose to use a new technique to control the angular alignment between layers in a vdW heterostructure combined with low temperature measurements of electron transport to reveal the phase diagram of the superconducting state and other strongly correlated effect. This phase diagram will allow us to understand the origin of the superconducting state as well as what are the parameters increasing the critical superconducting temperature. The successful candidates will participate actively in sample fabrication (assembly of vdW heterostructures, angular control of layers using an AFM, micro and nanofabrication processes) and electronic transport measurements at low temperatures.

Qualifications:  PhD in Physics or equivalent, experience in low temperature measurements, experience with micro and nano fabrication techniques for 2D materials is a bonus, and good communication skills in English (written and spoken).

Application: Send us an email with your CV, a motivation letter and arrange for three recommendation letters to be sent directly to us. For more information: https://bit.ly/30OplnQ