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Electronic dynamics and plasmons of sodium under compression
Ho-Kwang Mao1, Yang Ding, Yuming Xiao
1High Pressure Synergetic Consortium, and High Pressure Collaborative Access Team, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, IL 60439, USA. mao@gl.ciw.edu
Summary
Under high pressure, sodium (Na) exhibits complex electronic behavior. Its plasmon excitations deviate from simple free-electron models at extreme compressions, revealing unexpected metallic complexities.
Area of Science:
- Condensed Matter Physics
- Materials Science
- High-Pressure Physics
Background:
- Sodium (Na) is traditionally viewed as a simple metal.
- Under extreme pressure, simple metals can exhibit complex structural, optical, and electronic properties.
Purpose of the Study:
- To investigate the plasmon excitations of sodium (Na) under high pressure.
- To explore the electronic behavior of Na in body-centered cubic (BCC) and face-centered cubic (FCC) structures up to 97 GPa.
Main Methods:
- High-pressure compression of pure Na to 52 GPa (BCC) and 64-97 GPa (FCC).
- Momentum-dependent inelastic X-ray scattering (IXS) to study plasmon excitations.
- Ab initio calculations to interpret experimental results.
Main Results:
- The square of zero-momentum plasmon energy increased linearly with densification in BCC Na up to 1.5-fold.
- Deviations from linear behavior were observed in FCC Na above 64 GPa, with densification up to 3.7-fold.
- Plasmon dispersion curves showed pressure-dependent changes in both BCC and FCC phases.
Conclusions:
- The observed deviations in plasmon energy are consistent with Na remaining a simple metal under compression.
- High pressure induces complex electronic behavior in Na, challenging its simple metal classification.
- Inelastic X-ray scattering is a powerful tool for probing electronic properties of materials under extreme conditions.
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