Topological Electronic Transition Contributing to Improved Thermoelectric Performance in p-Type Mg₃Sb_{2- x}Bi_x Solid...

Area of Science:

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

Background:

• High band degeneracy (N_V) is crucial for optimizing thermoelectric performance.
• Topological electronic transitions offer a promising strategy to enhance N_V.

Purpose of the Study:

• To investigate the role of topological electronic transitions in p-type Mg₃Sb₂₋ₓBiₓ alloys.
• To correlate these transitions with enhanced thermoelectric properties.

Main Methods:

• Comprehensive spectroscopy characterizations.
• Theoretical calculations of electronic structures.
• Analysis of Fermi surface and valence band edge evolution.

Main Results:

• Demonstrated topological electronic transition from trivial semiconductor to topological semimetal in Mg₃Sb₂₋ₓBiₓ with increasing Bi content.
• Observed distinct Fermi surface evolution and multivalley valence band edge with N_V = 6 in Bi-rich compositions.
• Identified a unique two-step band inversion in Mg₃Bi₂.
• Achieved optimal thermoelectric power factor in p-type Mg₃Sb₀.₅Bi₁.₅.

Conclusions:

• Topological electronic transition is the key mechanism for elevating N_V in Mg₃Sb₂₋ₓBiₓ.
• The optimized Mg₃Sb₀.₅Bi₁.₅ exhibits superior thermoelectric performance.
• This work provides guidance for improving thermoelectric materials via topological strategies.