Mechanical and dielectric response within and beyond the linear regime

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Understanding material behavior under external stimuli is crucial.
• Dielectric and mechanical properties probe molecular and structural dynamics.
• Supercooled liquids and metallic glasses exhibit complex responses.

Purpose of the Study:

• To compare dielectric and mechanical responses of materials.
• To investigate linear and nonlinear response regimes.
• To elucidate the underlying mechanisms of observed phenomena.

Main Methods:

• Experimental measurements within the linear response limit.
• Experimental measurements beyond the linear response limit (high excitation amplitudes).
• Analysis of dielectric and shear-mechanical data.

Main Results:

• Linear dielectric and mechanical responses show identical temperature dependence, attributed to structural relaxation.
• Nonlinear mechanical experiments on metallic glasses indicate energies beyond k_BT, linked to microstructural plastic rearrangements.
• Nonlinear dielectric measurements on molecular glass-formers show energies below k_BT, attributed to field uptake or entropy changes, not plastic rearrangements.

Conclusions:

• Structural relaxation governs linear dielectric and mechanical responses.
• Nonlinear mechanical and dielectric responses stem from fundamentally different mechanisms.
• High electric fields do not typically trigger plastic rearrangements in molecular glass-formers.