I will present recent work on magnon-skyrmion crystal scattering in quantum Hall heterojunctions, which establish these neutral collective excitations of the quantum Hall ferromagnet, as a new probe for topology in such systems. In doing so, I will first review a series of pioneering experiments which allow for the emission and detection of such magnons in a scattering experiment setup. Then, I will explain a theoretical framework [1] to extract magnon scattering signatures for a skyrmion crystal a Wigner crystal where the charged particles have an associated topological invariant. This work will highlight how magnon diffraction can serve as an analogue for Bragg scattering, in suchcrystals. Finally, I will discuss work from a recent theory-experiment collaboration [2], which explores such scattering but in a different limit, where the magnons can be treated as particles, and their interaction with skyrmions can be thought of simplistically as Rutherford-type scattering. In this geometric optics limit, I will present the back-action of magnons on a linear array of confined skyrmions as an explanation for sharp and narrow windows of noise in the magnon detectors. I will also highlight the dipole nature of such magnons in quantum Hall ferromagnets and explore their dynamics in presence of a confining potential. I will end with a discussion on future use-cases of such quantum Hall magnons as a spin-valley entanglement witness, to detect complex internal entanglement patterns in multi-component skyrmion crystals [3], and also potentially as a resource for non-equilibrium exploration in the quantum Hall paradigm.
[1] N. Chakraborty, R. Moessner and B. Doucot: Physical Review B 112 (15), 155111
[2]R. Ayache*, N. Chakraborty* et. al:
[3] N. Chakraborty, R. Moessner and B. Doucot: Physical Review Letters 133 (20), 206604