Electromagnetic response of quantum Hall systems in dimensions five and six and beyond

TL;DR

This paper derives the electromagnetic response of quantum Hall systems in arbitrary dimensions, revealing how higher Chern numbers and phase space modifications influence their topological Hall conductivities, with potential experimental realizations.

Contribution

It provides a first-principles derivation of electromagnetic responses in high-dimensional QH systems and links phase space non-commutativity to quantized Hall conductivities.

Findings

Hall conductivity quantized by higher Chern numbers

Phase space density modification relates to non-commutativity

Unconventional responses appear with Fermi surfaces

Abstract

Quantum Hall (QH) states are arguably the most ubiquitous examples of nontrivial topological order, requiring no special symmetry and elegantly characterized by the first Chern number. Their higher dimension generalizations are particularly interesting from both mathematical and phenomenological perspectives, and have attracted recent attention due to a few high profile experimental realizations. In this work, we derive from first principles the electromagnetic response of QH systems in arbitrary number of dimensions, and elaborate on the crucial roles played by their modified phase space density of states under the simultaneous presence of magnetic field and Berry curvature. We provide new mathematical results relating this phase space modification to the non-commutativity of phase space, and show how they are manifested as a Hall conductivity quantized by a higher Chern number. When a Fermi surface is present, additional response currents unrelated to these Chern numbers also appear. This unconventional response can be directly investigated through a few minimal models with specially chosen fluxes. These models, together with more generic 6D QH systems, can be realized in realistic 3D experimental setups like cold atom systems through possibly entangled synthetic dimensions.