Funded Projects

Title: 2D crystalline thin films with non-trivial topology
Acronym: 2D-TOP
Leader: Evangelia Xenogiannopoulou
Start Date: 05/09/2018
End Date: 05/09/2021
Category: HFRI/GSRT


Τhe advent of graphene has generated an enormous interest in a number of other 2D crystals (silicene, germanene, transition metal dichalcogenides MX2), creating the prospect for exciting new versatile applications. In the ‘2D-TOP’ Project we attempt the “fusion” between 2D materials and topological quantum matter worlds with the aim to unveil new electronic states with unique properties. Τhe Project focuses on the experimental realization and physical characterization of two different classes of 2D crystals with a non-trivial topological order, namely the topological insulators (TI) and the topological Weyl semimetals (WSM). It is predicted, that stanene, a 2D layer of Sn atoms, is a TI with an energy band gap of approximately 0.1 eV, that conducts electricity only in 1D edge channels with virtually no heat dissipation and remarkable spin coherence over macroscale distances. In addition, the recent discovery of topological Weyl (WSM) opens new opportunities to store and/or process information by taking benefits from the selected chirality of Weyl Fermion bands. The 2D topological materials investigated in this Project could ultimately establish topology as paradigm shift for nanoelectronics and spintronics enabling a whole new line of technology for low power electronics. Taking into account that the continued scaling of CMOS becomes limited due to power dissipation, the topological materials could have a remarkable impact in the semiconductor market in the next years.

To achieve the objectives, crystalline 2D TI (stanene/bismuthene) and WSM (MTe2, M=Mo, W, Hf, Zr) will be grown by molecular beam epitaxy (MBE). Various Surface Science techniques will be employed in order to investigate the crystallinity, the topology-related valence band features and the electrical response of the topological materials, such as Reflection High Energy Electron Diffraction (RHEED),  X-Ray Diffraction (XRD), Raman spectroscopy, Scanning Tunneling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS) and Angle Resolved Photo-Electron Spectroscopy (ARPES).