Thermal transport in the Kitaev spin liquid under a staggered magnetic field

Many studies have been conducted to detect Majorana fermions as fractional spin excitations in the Kitaev spin liquids. For instance, the half-quantized thermal Hall effect was observed as evidence of the Majorana Chern insulator under a magnetic field [1]. Recently, engineering of the Majorana excitation spectrum was investigated [2], which would also help to identify the fractionalizations, but how to probe the modulated spectrum is yet to be fully clarified. In this talk, we study the Kitaev honeycomb model in both uniform and staggered magnetic fields which shows an asymmetric Majorana spectrum in momentum space. We show that the linear thermal current changes with the magnitudes and directions of the magnetic fields, reflecting the modulation of the Majorana spectrum. In addition, we find that the nonlinear (nonreciprocal) thermal current is induced by the asymmetry of the spectrum and also varies with the magnetic fields. We discuss the estimates of the thermal currents in a realistic situation and the possible experimental setup. [1] Y. Kasahara et al., Nature 559, 227 (2018); T. Yokoi et al., Science 373, 568 (2021). [2] D. Takikawa and S. Fujimoto, Phys. Rev. B 99, 224409 (2019); R. Chari, R. Moessner, and J. G. Rau, Phys. Rev. B 103, 134444 (2021).