Experimentelle Physik II


    VT-STM/AFM stands for Variable-Temperature Scanning Tunneling Microscope/Atomic Force Microscope.  In two aspects it is different to the other research instruments of our group.  First, it is not housed in a cryostat but rather connected to a cold finger through a flexible copper braid.  By controlling the flow of liquid helium through the cold finger and by accurately tuning the heating current applied to the sample holder this allows for adjusting the sample temperature in a relatively wide range from about 35 Kelvin up to 400 Kelvin. Second, the microscope cannot only be operated as an STM but also in the AFM mode, thereby extendig the range of potential sample systems to poorly conducting or even insulating surfaces. 

    In the past we made use of the variable-temperature capability of this instrument by investigating phase transition phenomena.  In particular, we studied the 5d transition metal dichalcogenide IrTe2 which exhibits charge modulations at low temperatures.   By imaging the surface at temperatures between room temperature and about 50 Kelvin we found a evidence for a hysteretic melting transition of a soliton lattice, a result we published in Physical Review Letters.