Barkhausen effects 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, between the T_d and 1T' phases in type-II Weyl semimetal MoTe₂. Thinning down the MoTe₂ crystal from bulk material to about 25nm results in a drastic strengthening of the hysteresis in the phase transition, with the difference in critical temperature increasing from ~40K to more than 300K. 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 defects. The distribution of the Barkhausen jumps shows a power law behavior, with its critical exponent α = 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.
Reference: C. Cao et al., 2D Materials 5, 044003 (2018)