Kavli Affiliate: Xiang Zhang
| First 5 Authors: Alvaro Bermejillo-Seco, Xiang Zhang, Maurits J. A. Houmes, Makars Šiškins, Herre S. J. van der Zant
| Summary:
A quantitative understanding of the microscopic mechanisms responsible for
damping in van der Waals nanomechanical resonators remains elusive. In this
work, we investigate van der Waals magnets, where the thermal expansion
coefficient exhibits an anomaly at the magnetic phase transition due to
magnetoelastic coupling. Thermal expansion mediates the coupling between
mechanical strain and heat flow and determines the strength of thermoelastic
damping (TED). Consequently, variations in the thermal expansion coefficient
are reflected directly in TED, motivating our focus on this mechanism. We
extend existing TED models to incorporate anisotropic thermal conduction, a
critical property of van der Waals materials. By combining the thermodynamic
properties of the resonator material with the anisotropic TED model, we examine
dissipation as a function of temperature. Our findings reveal a pronounced
impact of the phase transition on dissipation, along with transitions between
distinct dissipation regimes controlled by geometry and the relative
contributions of in-plane and out-of-plane thermal conductivity. These regimes
are characterized by the resonant interplay between strain and in-plane or
through-plane heat propagation. To validate our theory, we compare it to
experimental data of the temperature-dependent mechanical resonances of
FePS$_3$ resonators.
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