Klaus Ensslin: Quantum structures in 2D materials

posted 6 Apr 2017, 09:09 by Peter Boggild

Laboratory for Solid State Physics, ETH Zurich

2D crystals are ideal systems for the realization of strongly confined quantum structures. Many experiments have focused on etched graphene quantum devices because of the missing band. Most devices were dominated by localized states along the graphene edges, which are difficult to control on the atomic scale. In this talk I will present two solutions to this problem. In bilayer graphene a bandgap arises for vertical electric fields. We demonstrate that a split-gate arrangement can be used to define a narrow 1D ballistic channel. An additional well positioned top gate allows to pinch off the channel. Furthermore a series of plateau-like features occurs when the channel is opened. An interesting level scheme arises in particular for high magnetic fields. Another approach is based on MoS2 encapsulated between layers of BN to obtain best electronic quality. At low magnetic fields we observe a degeneracy of 6, which is explained by the 3-fold valley degeneracy in the conduction band of MoS2 plus a factor of 2 for spin-degeneracy. In a quantum point contact again conductance pinch-off and quantization is observed. 2D materials have improved to an extent, that novel electronic quantum devices can be realized with great promise.

1. H. Overweg, H. Eggimann, M.-H. Liu, A. Varlet, M. Eich, P. Simonet, Y. Lee, K. Watanabe, T. Taniguchi, K. Richter, V. I. Fal'ko, K. Ensslin, and T. Ihn, “Oscillating magnetoresistance in graphene p-n junctions at intermediate magnetic fields”, arXiv:1612.07624

2. R. Pisoni, Y. Lee, H. Overweg, M. Eich, P. Simonet, K. Watanabe, T. Taniguchi, R. Gorbachev, T. Ihn, and K. Ensslin“Quantized conductance and broken symmetry states in MoS2 van der Waals heterostructures” , arXiv:1701.08619

Klaus Ensslin received his B. Sc. from the University of Munich, his M. Sc. from ETH Zurich, and his PhD from Max Planck Institute in Stuttgart. He moved on to postdocs at UC Santa Barbara and University of Munich and started as a professor at ETH Zurich in 1995. Since 2011 Klaus Ensslin is the Director of National Center for Competence in Research on “Quantum Science and Technology”.