IAP Seminar (Orbital texture and its effects in electronic transport)
Nontrivial electronic structures in the crystal momentum space have received great attention in modern condensed matter physics. For instance, nonuniform phase of an electronic wave function in the momentum space may give rise to a nonzero Berry curvature and corresponding anomalous Hall transport. Similarly, if an electronic structure forms a spin texture in the momentum space, it may result in so-called the spin Berry curvature and the corresponding spin Hall effect, which are not only fundamentally interesting but also promising for the next generation device applications. Since the spin degree of freedom does not directly couple to the position and momentum degrees of freedom, taking into account the orbital degree of freedom is crucial for understanding the anomalous transport of electrons. The purpose of this talk is to shed light on its general understanding by introducing the concept of the orbital texture. The orbital texture is an orbital version of spin texture, but its understanding requires a far deeper concept, the orbital angular position and the orbital torsion, which are results of algebraic difference between the spin and orbital angular momentum operators. Similarly to the conventional and spin Berry curvatures, the orbital texture gives the orbital Berry curvature which describes the orbital Hall effect. The orbital texture not only provides a useful platform for understanding of known phenomena but also reveals several features of the orbital transport that are absent in spin and charge transport.