Experimentelle Physik II


LT-1 stands for Low-Temperature scanning tunneling microscope #1 as it was the first of its kind commissioned at our research group.  The microscope is cooled by liquid helium and typically operated at a temperature of 5 Kelvin, which corresponds to -268.15 °C or -450.67 °F, but the sample temperature can be raised by a dedicated button heater up to about 130 K.  In order to reach such a low temperature the microscope needs to be screened from any ambient thermal radiation.  Therefore, it is located within a cryostat behind radiation shield.  To maintain highly controlled conditions samples and tips are prepared under ultra-high vacuum (UHV) conditions, i.e. at a pressure about 13 orders of magnitude lower than in ambient environment. The LT-1 is protected from environmental noise by springs and an eddy current damping system; the remaining noise is at about 1-2 pm (picometer), about one hundrets of the diameter of an atom.

The LT-1 is mainly used to investigate the electronic properties of topological and/or strongly spin-orbit-coupled sample systems, such as binary chalchogenides (e.g. Bi2Te3) or Rashba surfaces.  We are particularly interested in the interaction of surface electrons with magnetic and non-magnetic adatoms which are deliberately deposited by evaporation on the cooled sample (see, e.g., this example).