Colossal Nernst power factor in topological semimetal NbSb₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Technology

Background:

• Solid-state cooling below 77 K is vital for quantum information and probing quantum states.
• Current technologies are limited by the scarcity of effective thermoelectric and thermomagnetic materials.

Purpose of the Study:

• To discover novel materials for advanced solid-state cooling below liquid nitrogen temperature.
• To investigate the thermomagnetic properties of topological semimetals.

Main Methods:

• Experimental synthesis and characterization of topological semimetal NbSb2 single crystals.
• Measurement of Nernst power factor and Nernst figure-of-merit under applied magnetic fields (5 T) at cryogenic temperatures (20-25 K).
• Analysis of electronic structure and phonon-drag effects contributing to thermomagnetic performance.

Main Results:

• Discovery of colossal Nernst power factor (3800 × 10^-4 W m^-1 K^-2 at 25 K) and high Nernst figure-of-merit (71 × 10^-4 K^-1 at 20 K) in NbSb2.
• Observed high performance attributed to large Nernst thermopower, high longitudinal conductivity, and low transverse thermal conductivity.
• Identified unique electronic structure with compensated high-mobility electrons/holes and strong phonon-drag effect as key factors.

Conclusions:

• NbSb2 single crystals demonstrate unprecedented thermomagnetic performance at cryogenic temperatures.
• The findings pave the way for developing new solid-state heat-pumping materials for sub-77 K applications.
• This research significantly contributes to advancing quantum technology infrastructure.