Enhanced thermoelectric performance of heavy-fermion compounds Yb TM 2Zn20 (TM = Co, Rh, Ir) at low temperatures

Kaya Wei; Jennifer N Neu; You Lai; Kuan-Wen Chen; Dean Hobbis; George S Nolas; David E Graf; Theo Siegrist; Ryan E Baumbach

doi:10.1126/sciadv.aaw6183

Enhanced thermoelectric performance of heavy-fermion compounds Yb TM ₂Zn₂₀ (TM = Co, Rh, Ir) at low temperatures

Sci Adv. 2019 May 31;5(5):eaaw6183. doi: 10.1126/sciadv.aaw6183. eCollection 2019 May.

Authors

Kaya Wei¹, Jennifer N Neu^{1

2}, You Lai^{1

2}, Kuan-Wen Chen^{1

2}, Dean Hobbis³, George S Nolas³, David E Graf¹, Theo Siegrist^{1

4}, Ryan E Baumbach^{1

2}

Affiliations

¹ National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA.
² Department of Physics, Florida State University, Tallahassee, FL, USA.
³ Department of Physics, University of South Florida, Tampa, FL, USA.
⁴ Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL, USA.

Abstract

Thermoelectricity allows direct conversion between heat and electricity, providing alternatives for green energy technologies. Despite these advantages, for most materials the energy conversion efficiency is limited by the tendency for the electrical and thermal conductivity to be proportional to each other and the Seebeck coefficient to be small. Here we report counter examples, where the heavy fermion compounds YbTM ₂Zn₂₀ (TM = Co, Rh, Ir) exhibit enhanced thermoelectric performance including a large power factor (PF = 74 μW/cm-K²; TM = Ir) and a high figure of merit (ZT = 0.07; TM = Ir) at 35 K. The combination of the strongly hybridized electronic state originating from the Yb f-electrons and the novel structural features (large unit cell and possible soft phonon modes) leads to high power factors and small thermal conductivity values. This demonstrates that with further optimization these systems could provide a platform for the next generation of low temperature thermoelectric materials.