Bauer, G.教授

【研究概要】Bauer, G. 教授

Polarization caloritronics for heat management

Spin caloritronics is a lively field that studies the spin degree of freedom in thermoelectric and thermomagnetic phenomena, such as the spin Seebeck and spin Peltier effects in magnetic materials and devices [1]. We recently studied the option to replace magnets by ferroelectrics [2], i.e. the electron magnetic moment or spin by electric dipoles and spin waves or magnons by polarization waves or ferrons [3-5]. We predicted polarization Seebeck and Peltier effects as in Fig 1. Another observable is the electric field-dependent heat conductance observed recently by the Ohio State University group, finding good agreement of measurements with theory [6]. This device could be used a heat switch. 

Fig. 1: (Left panel) A voltage biased ferroelectric capacitor. (Right panel) A temperature bias over the capacitor leads to a polarization current and polarization accumulation on the scale of the polarization relaxation length that can be measured as a dc thermovoltage [2].
Fig. 2: A temperature gradient over the interleaved pile made from interleaved films of silver and the ferroelectric PZT leads to the heat current Jq. The heat conductivity k turns out to be modulated by the applied voltage and polarization P which is evidence for ferrons [6]. The right panel illustrates the good agreement between observations and model calculations (red line) for  where E is the electric field.

[1] G.E.W. Bauer, E. Saitoh, and B.J. van Wees, “Spin Caloritronics”, Nat. Mat. 11, 391 (2012).

[2] G.E.W. Bauer, R. Iguchi, and K. Uchida, “Theory of Transport in Ferroelectric Capacitors”, Phys. Rev. Lett. 126, 187603 (1-4) (2021).

[3] P. Tang, R. Iguchi, K. Uchida and G.E.W. Bauer, “Thermoelectric Polarization Transport in Ferroelectric Ballistic Point Contacts”, Phys. Rev. Lett. 128, 047601 (1-6) (2022).

[4] P. Tang, R. Iguchi, K. Uchida, and G.E.W. Bauer, “Excitations of the ferroelectric order”, Phys. Rev. B 106, L081105 (2022).

[5] P. Tang, K. Uchida, and G.E.W. Bauer, “Nonlocal Drag Thermoelectricity Generated by Ferroelectric Heterostructures”, arXiv:2207.00240 . 

[6] B.L. Wooten, R. Iguchi, P. Tang, J. S. Kang,4 K. Uchida, G.E.W. Bauer, J.P. Heremans, “Electric-field dependent phonon spectrum and heat conduction in ferroelectrics”, Sc. Adv., to be published.