Orbital Hall effect in two-dimensional materials*

I will explore orbital effects in two-dimensional (2D) materials and the potential implications they hold. A central theme of my presentation will be the orbital Hall effect (OHE), a phenomenon closely related to the spin Hall effect (SHE). The OHE, much like the SHE, gives rise to a transverse flow of angular momentum due to a longitudinally applied electric field. However, what sets it apart is its distinct origin, emerging from the interplay between orbital attributes and crystal symmetries, free from reliance on spin-orbit coupling.

I will discuss various aspects of the OHE within the realm of 2D materials. Specifically, I will showcase how monolayers and bilayers of transition metal dichalcogenides (TMDs) display the OHE phenomenon, in their insulating phase [1]. These TMDs, when cut along precise orientations, host conductive edge states that traverse the bulk energy gap. This unique characteristic facilitates the transport of orbital angular momentum [2].

Furthermore, I will explore the emergence of the orbital Edelstein effect in 2D materials with lower symmetry [3], shedding light on its implications. The outcomes of our research offer the prospect of utilizing 2D materials for injecting orbital currents and facilitating orbital torque transfer, potentially surpassing the capabilities of their spin-based counterparts. 

[1] Tarik P. Cysne, Marcio Costa, Luis M. Canonico, M. Buongiorno Nardelli, R. B. Muniz, Tatiana G. Rappoport , Phys. Rev. Lett. 126, 056601(2021). 

[2] Marcio Costa, Bruno Focassio, Tarik P. Cysne, Luis M. Canonico, Gabriel R. Schleder, Roberto B. Muniz, Adalberto Fazzio, Tatiana G. Rappoport, Phys. Rev. Lett. 130, 116204 (2023). 

[3] Tarik P. Cysne, Marcio Costa, M. Buongiorno Nardelli, R. B. Muniz, Tatiana G. Rappoport, arXiv:2307.03866.