Strongly correlated oxides for energy harvesting

Abstract

We review recent advances in strongly correlated oxides as thermoelectric materials in pursuit of energy harvesting. We discuss two topics: one is the enhancement of the ordinary thermoelectric properties by controlling orbital degrees of freedom and orbital fluctuation not only in bulk but also at the interface of correlated oxides. The other topic is the use of new phenomena driven by spin-orbit coupling (SOC) of materials. In 5d electron oxides, we show some SOC-related transport phenomena, which potentially contribute to energy harvesting. We outline the current status and a future perspective of oxides as thermoelectric materials.

Keywords: 210 Thermoelectronics / Thermal transport / insulators; 50 Energy Materials; Dirac semimetal; Seebeck effect; Thermoelectric materials; Weyl semimetal; anomalous Nernst effect; magnetic skyrmion; spin Hall effect; spin Seebeck effect; strongly correlated oxides.

Graphical abstract

Figure 1.

(a) Crystal structure of hollandite $\mathrm{B}{\mathrm{a}}_{\mathrm{x}}\mathrm{T}{\mathrm{i}}_8{\mathrm{O}}_{16+\delta }$. (b)(c) Temperature dependence of (b) the resistivity and (c) the Seebeck coefficient along the c axis (the chain direction) for $\mathrm{B}{\mathrm{a}}_{\mathrm{x}}\mathrm{T}{\mathrm{i}}_8{\mathrm{O}}_{16+\delta }$ with various values of n. Reproduced with permission from [10,11].

Figure 2.

(a)(b) Temperature dependence of the thermal conductivity for (a) BaV₁₀O₁₅ and SrV₁₀O₁₅ and (b) $\mathrm{B}\mathrm{a}\mathrm{T}{\mathrm{i}}_8{\mathrm{O}}_{16+\delta }$. Reproduced with permission from [11,29].

Figure 3.

(a) Calculated variation in the temperature after a pump pulse is applied to (SrVO₃ 30 nm–SrTiO₃ 30 nm)₂ on (La,Sr)(Al,Ta)O₃ (LSAT) substrate, where the interface thermal resistance between SrVO₃ and SrTiO₃$R_I=2.5\times {10}^{-9}$ Km²/W is assumed. (b) Experimental time dependence of the reflectivity change at $\mathrm{\hslash }\omega =1.2$ eV for (SrVO₃ 30 nm–SrTiO₃ 30 nm)₂ (a solid line) and the calculated result based on (a) (a dashed line). Reproduced with permission from [32].

Figure 4.

(a) Schematic view of Weyl band dispersion and structure of Weyl points in momentum space for (Nd_0.5Pr_0.5)₂ Ir₂O₇. Red and blue symbols denote the Weyl points. (b) Two variants of all-in all-out magnetic structure (c) Electronic phase diagram for Nd₂Ir₂O₇ under the hydrostatic pressure and (Nd_0.5Pr_0.5)₂Ir₂O₇. (d) Hall resistivity and (e) magnetization for (Nd_0.5Pr_0.5)₂Ir₂O_7.

Figure 5.

(a) Schematic of Dirac band dispersion for SrIrO₃. Temperature dependence of (b) resistivity and Hall coefficient (replotted from [51]) and (c) Seebeck and Nernst coefficient for polycrystalline SrIrO_3.

Figure 6.

Experimentally measured values of spin Hall resistivity ${\rho }_{\mathrm{S}\mathrm{H}}$ for various metals are plotted as a function of electrical resistivity ${\rho }_{\mathrm{C}}$. Replotted with permission from [61], © 2013 Macmillan Publishers Limited.

Figure 7.

(a) Magnetic field dependence of Hall resistivity (${\rho }_H$) of the (SrRuO₃)_m-(SrIrO₃)₂ bilayers ($m=5$) at various temperatures. (b) Contributions from AHE and THE of $m=5$ at 80 K. (c) Color map of topological Hall resistivity in the $T-H$ plane for $m=5$. Black open and filled symbols represent coercive field ($H_c$) and the field at which topological Hall resistivity reaches its maximum ($H_p$), respectively. From [67], © 2016 American Association for the Advancement of Science.