Barkhausen effect in the first order structural phase transition in type-II Weyl semimetal MoTe2

We report the first observation of the non-magnetic Barkhausen effect in van der Waals layered crystals, specifically, during transitions between the T-d and 1T' phases in type-II Weyl semimetal MoTe2. Thinning down the MoTe2 crystal from bulk material to about 25 nm results in a drastic strengthening of the hysteresis in the phase transition, with the difference in critical temperature increasing from similar to 40 K to more than 300 K. The Barkhausen effect appears for thin samples and the temperature range of the Barkhausen zone grows approximately linearly with reducing sample thickness, pointing to a surface origin of the phase pinning effects. The distribution of the Barkhausen jumps shows a power law behavior, with its critical exponent alpha = 1.27, in good agreement with existing scaling theory. Temperature-dependent Raman spectroscopy on MoTe2 crystals of various thicknesses shows results consistent with our transport measurements.