Intrinsic anharmonic localization in thermoelectric PbSe.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Lead chalcogenides, such as lead selenide (PbSe), possess excellent thermoelectric properties.
• Low thermal conductivity in these materials is linked to complex anharmonic lattice dynamics.
• The phonon glass-electron crystal concept guides research towards materials that scatter phonons while preserving electron transport.

Purpose of the Study:

• To experimentally investigate high-temperature phonon localization in PbSe.
• To explore the role of anharmonic dynamics in altering vibrational transport properties.
• To understand the fundamental physics governing phonon behavior in PbSe.

Main Methods:

• High-temperature neutron scattering experiments were conducted on PbSe.
• Analysis focused on phonon dynamics, including group velocity and scattering mechanisms.
• Simulations suggested the potential for intrinsic localized modes in PbSe.

Main Results:

• Experimental observation of high-temperature phonon localization in PbSe.
• Development of zero group velocity for a significant portion of the transverse optic phonon above a critical temperature.
• Unusual sharpening of the longitudinal acoustic mode due to reduced phonon scattering phase space.

Conclusions:

• Anharmonic dynamics in PbSe can lead to phonon localization beyond isolated modes.
• Nonlinear physics significantly impacts vibrational transport, offering new avenues for thermoelectric material design.
• The findings demonstrate a fundamental alteration of phonon propagation due to anharmonic effects.