Dzyaloshinskii-Moriya interaction from unquenched orbital angular momentum

Orbitronics is an emerging and fascinating field that explores the utilization of the orbital degree of freedom of electrons for information processing. An increasing number of orbital phenomena are being currently discovered, with spin-orbit coupling mediating the interplay between orbital and spin effects, thus providing a wealth of control mechanisms and device applications. In this context, the orbital analog of the spin Dzyaloshinskii-Moriya interaction (DMI), i.e., orbital DMI , deserves to be explored in depth since it is believed to be capable of inducing chiral orbital structures. Here, we unveil the main features and microscopic mechanisms of the orbital DMI in a two-dimensional square lattice using a tight-binding model of t 2 g orbitals in combination with the Berry phase theory. This approach allows us to investigate and transparently disentangle the role of inversion symmetry breaking, strength of orbital-exchange interaction, and spin-orbit coupling in shaping the properties of the orbital DMI. By scrutinizing the band-resolved contributions, we are able to understand the microscopic mechanisms and guiding principles behind the orbital DMI and its anisotropy in two-dimensional magnetic materials, and uncover a fundamental relation between the orbital DMI and its spin counterpart, which is currently being explored very intensively. The insights gained from our work contribute to advancing our knowledge of orbital-related effects and their potential applications in spintronics, providing a path for future research in the field of chiral orbitronics.