High-frequency subsurface and bulk dynamics of liquid indium

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• Understanding the unique properties of liquid metals at their surfaces is crucial for various applications.
• Previous studies have indicated potential differences in dynamics between bulk and surface regions of liquids.
• Generalized hydrodynamic models provide a framework for describing liquid dynamics, but require experimental validation.

Purpose of the Study:

• To investigate the dynamic properties of liquid indium, particularly focusing on differences between bulk and near-surface regions.
• To experimentally determine the longitudinal viscosity of liquid indium with high energy resolution.
• To validate and refine generalized hydrodynamic models using experimental data.

Main Methods:

• Performed inelastic x-ray scattering (IXS) experiments on liquid indium.
• Utilized a high energy resolution of 3 meV for precise measurements.
• Employed a generalized hydrodynamic model incorporating structural and microscopic relaxation processes for data analysis.

Main Results:

• Experimental data were successfully reproduced by the generalized hydrodynamic model.
• A significantly higher longitudinal viscosity (22 mPa s) was measured in the near-surface region compared to the bulk (7.4 mPa s).
• The increased surface viscosity is attributed to a slowing down of collective dynamics within a subsurface region of approximately 4.6 nm.

Conclusions:

• Liquid indium exhibits distinct dynamic behavior at its surface compared to its bulk.
• The enhanced longitudinal viscosity at the surface is a direct consequence of altered collective dynamics.
• The findings support the validity of generalized hydrodynamic models for describing complex liquid dynamics, including surface effects.