Colossal Nernst power factor in topological semimetal NbSb₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Technologies

Background:

• Solid-state cooling below 77 K is crucial for quantum technologies but limited by material availability.
• Existing thermoelectric and thermomagnetic materials are insufficient for sub-liquid nitrogen temperatures.

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 NbSb2 single crystals.
• Measurement of Nernst power factor and Nernst figure-of-merit under magnetic fields.
• Analysis of electronic structure and transport properties.

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.
• NbSb2 exhibits high thermomagnetic performance due to large Nernst thermopower, high electrical conductivity, and low thermal conductivity.
• Large Nernst thermopower attributed to compensated high-mobility electrons/holes and phonon-drag effect.

Conclusions:

• NbSb2 is a promising material for solid-state cooling technologies operating below liquid nitrogen temperatures.
• This discovery opens new avenues for material exploration in low-temperature heat pumping.
• The unique electronic structure and phonon-drag effect in NbSb2 are key to its high performance.