Low-Temperature Scanning Tunneling Microscope commissioned at CMU

  • By Ke Xu
  • 14 August 2018

A low-temperature scanning tunneling microscope (LT-STM) has recently been commissioned at Carnegie Mellon University, and is available for use by external users. Obtained through a grant from the National Science Foundation (with cost sharing from CMU), the instrument allows atomic-resolution studies of surface structure and spectroscopic studies of electronic states within a few eV on either side of the Fermi energy. Base temperature is 7 K, and there is a magnetic field capability of up to 2T perpendicular to the sample surface.

First results have been obtained by a team led by Randall Feenstra and Ben Hunt, working with postdoc Felix Lupke, grad student Dacen Waters, and undergrads Nicolas Iskos and Nick Speeney. They studied a two-dimensional (2D) material, Tungsten Ditelluride (WTe2), that is mostly an insulator whose charge carriers cannot conduct electricity. However, at low temperatures charge carriers on the surface of the material (or edge for the case of a 2D sample) can conduct electricity in a robust way insensitive to the presence of any defects. This makes WTe2  a topological insulator, with properties that will likely spur technological innovations such as spintronics and quantum computing.

Users interested in utilized the LT-STM should contact Prof. Feenstra (feenstra@cmu.edu).