Engineering Anomalously Large Electron Transport in Topological Semimetals

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Topological semimetals exhibit anomalous transport properties with mobilities far exceeding single-particle predictions.
• The underlying mechanisms for these enhanced transport properties remain largely unexplained, hindering material design.

Purpose of the Study:

• To elucidate the origin of anomalous transport in topological semimetals.
• To investigate the role of phonon-electron scattering in enhancing electron mobility.
• To provide insights for engineering topological semimetals for specific applications.

Main Methods:

• Combined de Haas-van Alphen (dHvA) measurements, electron transport, and Raman scattering.
• Utilized first-principles calculations to analyze electron and phonon dispersions.
• Systematically studied topological semimetals MX2 (M = Nb, Ta; X = Ge, Si) by substituting Ge with Si.

Main Results:

• Demonstrated that phonon-electron scattering, dominating over phonon-phonon scattering, is responsible for significant mobility enhancements.
• Observed a dramatic reduction in mobility enhancement when Ge was replaced by Si, bringing it closer to single-particle values.
• Confirmed that these changes occurred without altering crystal structure, topology, or significantly increasing disorder.

Conclusions:

• Phonon-drag, driven by dominant phonon-electron scattering, is the primary cause of anomalous transport in topological semimetals.
• Tuning electron-phonon interactions offers a viable strategy for controlling and optimizing transport properties.
• This work provides a fundamental understanding crucial for the development of next-generation optoelectronic and nanoscale devices.