Sensitive measurement of the Kosterlitz-Thouless transition

We have developed a new technique for probing the Kosterlitz - Thouless transition in thin helium films. The technique is based on operation of a single quartz crystal microbalance at two different harmonic frequencies simultaneously. The technique is insensitive to surface effects, and provides the means for monitoring the heating of the film, By suppressing heating and surface effects we were able to systematically compare the results with the existing theories of ANHS, Bowley, Armour and Benedict, and Armour and Bowley. Substantial agreement with the last model of Armour and Bowley was observed. To the best our knowledge this is the first time that the experimental data in the frequency range 10-30NMz is compared to theoretical models.