Kakeru Tanaka | Searcharxiv

arXiv2026

Raytracing and quantifying the inferior mirage

Using custom raytracing code, we explore several features of the inferior mirage that are not widely discussed, such as the blurring in the mirage image, and what happens to the light in the direct image region that is replaced by the mirage image. The raytracing model also clarifies how to quantify the mirage, and we provide expressions to calculate the angular extent of the mirage under given thermal conditions and measurement geometry.

physics.optics↗

arXiv2026

Nonlinear response theory for orbital photocurrent in semiconductors

Recent theoretical studies on the nonlinear response of spin and orbital degrees of freedom have discovered spin and orbital analogs of the photocurrent, with potential for characterizing topological materials and for applications. In this paper, we develop a general theory for calculating spin and orbital currents in semiconductors and study the properties of optical responses in the Bernevig-Hughes-Zhang and Luttinger models, where nonlinear orbital responses and a topological phase transition occur. We study the evolution of optical responses at the topological phase transition and how they manifest. In addition, we find that the relaxation time dependence of the orbital conductivity is somewhat distinct from that of the photocurrent. The theory is straightforwardly applicable to complex models of real materials, allowing quantitative predictions of the nonlinear responses of orbital and spin.

cond-mat.mes-hall↗