Anisotropic and electric-field dependent heat conduction in CuO*

CuO is unique among insulating transition-metal monoxides in possessing monoclinic crystal structure and complex magnetic phases. It received renewed attention in the past decade for multiferroicity^a in its spiral antiferromagnetic phase (213 K < T < 230 K) and quasi-one-dimensional magnetism at higher temperatures.^b We will discuss the temperature and electric field dependent thermal conductivity (κ) measured on high-quality single crystals^c along the principal crystallographic axes. Modest electric fields (up to ~5 kV/cm) were applied along the [010] direction, transverse to the heat flow. A remarkably strong reduction of κ (up to 60% near room temperature) is associated with charge flow from a very small density of charge carriers, correlating with the sample conductivity. Possible mechanisms for this effect will be discussed.

^a T. Kimura et al., Nat. Mater. 7, 291 (2008).
^b H. Jacobsen et al., Phys. Rev. B 97, 144401 (2018).
^c A. Rebello, Z. C. M. Winter, S. Viall, and J. J. Neumeier, Phys. Rev. B 88, 094420 (2013).