Past Events

The moiré system involving stacked two-dimensional materials has become a particularly intriguing platform in recent years, thank to its flexible tunability and applicability, especially in subfields like Twistronics and Straintronics. Meanwhile, the emergence of layer as a quantum degree-of-freedom has made possible many fascinating properties unique to layered structures. The Bloch electrons carrying the layer pseudospin can exhibit anomalous polarization/transport responses when coupled to fields that are ordinarily unresponsive, which also shape the quantum geometry in momentum and extended parameter spaces. In short, I will provide a multifaceted theoretical investigation of the twist, strain, and magnetic control of the electronic and excitonic states in van der Waals (vdW) moiré materials.

 

In this Defense, we first unveil efficient control of layer polarizations in vdW layered structures with an in-plane electric field, akin to the Edelstein effect. Such response is rooted in several intrinsic band geometric quantities defined in extended parameter spaces characteristic of layer hybridized electrons. Rich linear and nonlinear effects of multipole responses emerge in TMD trilayers. Turning towards the magnetic control, the intrinsic planar Hall effect induced from the layer pseudospin will be introduced, where electron’s orbital with layer components will couple to the in-plane magnetic field, breaking time reversal symmetry. We access the Hall current responding to linear and nonlinear order of the electric field and apply formalism to the twisted bilayer graphene. For excitonic states, in-plane magnetic field will influence the dipolar IXs through magneto-Stark effect, and chiral light-matter interface can be realized by hybridizing with intralayer excitons in TMD homobilayers with BN inserted.