Electron-Phonon Interactions in Piezoelectric Crystals and the Missing Quadrupole Term

Research Overview

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Former Resnick Fellow, Vatsal Jhalani, is a member of a research team that developed a more accurate method to study the long-range interactions between electrons and lattice vibrations in piezoelectric (PE) materials. The team's publication, "Piezoelectric Electron-Phonon Interaction from Ab Initio Dynamical Quadrupoles: Impact on Charge Transport in Wurtzite GaN", demonstrates a quantitative framework to compute the e-ph interaction due to the quadrupole term. The approach is applied to wurtzite GaN, a PE crystal, and is shown to accurately capture all short- and long-range interactions between electrons and phonons. Calculations of electronic scattering processes and mobilities in GaN are also shown, providing new insights on the electrical properties of PE materials.

Scientific Achievement

Development of a more accurate computational method to study the electron dynamics in piezoelectric (PE) materials.

Significance and Impact

A quantitative framework enabling accurate calculations of long-range interactions between electrons and lattice vibrations in PE materials.

Due to thermal atomic motions, electrons in a material feel changes in their potential energy due to both short-range and long-range electrostatic forces. An intermediate type of long-range electron-phonon (e-ph) interaction arises in piezoelectric crystals, where strain induced by acoustic phonons results in quadrupole-like potential terms. Our quantitative framework computes the e-ph interaction due to the quadrupole term for more accurate studies of electron dynamics in PE. Credit: Bernardi Group. Reprinted with permission from authors. DOI:10.1103/PhysRevLett.125.136602 Credit: Bernardi Research Group Caltech

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Due to thermal atomic motions, electrons in a material feel changes in their potential energy due to both short-range and long-range electrostatic forces. An intermediate type of long-range electron-phonon (e-ph) interaction arises in piezoelectric crystals, where strain induced by acoustic phonons results in quadrupole-like potential terms. Our quantitative framework computes the e-ph interaction due to the quadrupole term for more accurate studies of electron dynamics in PE. Credit: Bernardi Group. Reprinted with permission from authors. DOI:10.1103/PhysRevLett.125.136602

Credit: Bernardi Research Group Caltech

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Technical Details

• The framework computes the e-ph interaction due to the quadrupole term.
• Applied to wurtzite GaN, a PE crystal, and showed all short- and long-range interactions between electrons and phonons are accurately captured.

Jhalani, Vatsal A. and Zhou, Jin-Jian and Park, Jinsoo and Dreyer, Cyrus E. and Bernardi, Marco. Piezoelectric Electron-Phonon Interaction from Ab Initio Dynamical Quadrupoles: Impact on Charge Transport in Wurtzite GaN (2020) Physical Review Letters, 125 (13). DOI: 10.1103/PhysRevLett.125.136602

Contact: Marco Bernardi