EventDetails

Speaker:
Prof. Dr. Michele Governale, School of Chemical and Physical Sciences and Mac Diarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington (New Zealand)

Quantum rings are paradigmatic systems to study phenomena associated with geometrical phases such as the
Aharano-Bohm and Aharonov-Casher effects as well as their non-Abelian generalisations. We present a unified
approach [1] to study of quantum rings realised in materials where the charge carriers mimic two-dimensional
Dirac electrons, including single-layer graphene, single-layer transition-metal dichalcogenides and quantum
wells in narrow-gap semiconductors. We develop a general theoretical description of the ring sub-band
structure based on a k • p approach. This theoretical framework is used to derive an effective Hamiltonian for
the azimuthal motion of the charge carriers in the ring that yields a deeper insight into the physical origin of the
observed transport effects. In particular, we consider the ring attached to leads and we calculate the twoterminal
conductance by means of the scattering approach to mesoscopic transport. We focus on the effect of
the interplay of pseudospin chirality and quantum confinement on the geometric phase, a quantity
experimentally accessible through conductance measurements. For example, the transition between massless-
Dirac and Schrödinger-like behaviour manifests itself clearly in the interference pattern of the conductance. The
dependence of interference effects on the charge carriers’ flavour degree of freedom opens up the possibility to
use quantum rings as flavourtronic devices.

[1] L. Gioia, U. Zülicke, M. Governale, and R. Winkler, Phys. Rev. B 97, 205421 (2018).