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InNaTo

Investigation of nanoscale properties of topological Weyl semimetals
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Overview

The aim of the project InNaTo is to examine the nanoscale properties of topological materials (e.g. Weyl semimetals) with a particular focus on the correlation between microstructure, composition and magnetotransport properties in the topological chiral semimetal CoSi. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska–Curie grant agreement No 898113. InNaTo started in July 2020 and ran until June 2022. The principal investigator is Dr. Alan Molinari.

InNaTo is divided into two main subprojects:

  1. Growth and characterization of CoSi thin films (thickness ≈ 20 nm) prepared by molecular beam epitaxy. The goal is to understand the impact of film microstructure and chemical composition on the magnetotransport properties and to search for potential anomalies in the magnetoresistance and Hall effect signals.
  2. Fabrication and testing of CoSi microscale Hall bars prepared by focused ion beam milling. These microscale CoSi Hall bars serve as a valuable reference between bulk single crystals and nanoscale thin films.

The CoSi samples have been systematically characterized using a variety of experimental methods, including for instance grazing-incident X-ray diffraction, X-ray reflectivity, atomic force microscopy and scanning transmission electron microscopy. The (magneto)transport properties (4-point resistivity, transverse and longitudinal magnetoresistance and Hall effect) are analyzed in a physical properties measurement system in a temperature range of 1.8 – 400 K and applied magnetic fields up to 9 T. Figures 1 and 2 show some representative experimental results obtained in case of nanoscale CoSi thin films and microscale CoSi Hall bars.

Grazing-incident X-ray diffraction of CoSi films grown at different temperatures (left). 4-point resistivity (center) and transverse magnetoresistance (right) of a representative CoSi film
Figure 1: Grazing-incident X-ray diffraction of CoSi films grown at different temperatures (left). 4-point resistivity (center) and transverse magnetoresistance (right) of a representative CoSi film grown at 360 ˚C.
Scanning electron micrograph of a CoSi micro-scale Hall bar and magnetoresistance at 1.7 K upon variation of the angle between the applied magnetic field and the current density
Figure 2: Scanning electron micrograph of a CoSi micro-scale Hall bar prepared by focused ion beam milling (left). Magnetoresistance at 1.7 K upon variation of the angle between the applied magnetic field and the current density J (right).

Publications