Magnetoresistance due to classical memory effects in 3D conductors
Dr. Sarbajaya Kundu
Postdoctoral Research Associate
Department of Physics and Astronomy, University of Notre Dame
Postdoctoral Research Associate
Department of Physics and Astronomy, University of Notre Dame
Abstract follows below.
Optical absorption signatures to probe van-Hove fermiology
Dr. Hyeok-Jun Yang
Society of Science Research Fellow
Department of Physics and Astronomy, University of Notre Dame
Society of Science Research Fellow
Department of Physics and Astronomy, University of Notre Dame
Abstract follows below.
Dr. Kundu's abstract: Magnetoresistance (MR) provides a powerful tool for probing the non-Markovian nature of transport in a magnetic field. In the semiclassical limit, sufficiently long-range disorder can give rise to a nontrivial magnetoresistance due to classical memory effects, associated with multiple returns of electron trajectories between scattering events. Such non-Markovian effects can be taken into account within the semiclassical Boltzmann equation, provided the disorder is treated as a random force term in the Liouville operator. While the presence of such disorder has been indicated in different materials, there have been few rigorous studies on these effects in 3D systems. In this talk, I will be discussing our recent results for the semiclassical magnetoresistivity due to a weak, long-range a) random magnetic field (RMF), b) random potential (RP) in a 3D electron gas at classically strong fields. For our analysis, we write down a perturbative expansion for the Green’s function of the modified Liouville operator, and therefore for the conductivity, in the correlation function of long-range disorder. In the absence of short-range disorder, the Green’s function is found to be singular due to a zero mode, and the field-dependence of the conductivity is obtained by re-summing the perturbation series to all orders. We find a significant transverse as well as longitudinal magnetoresistance, with different field-dependencies, which either peak, or saturate, at a characteristic field scale, where the correlation length of the disorder becomes comparable to the cyclotron radius.
Dr. Yang's abstract: Van-Hove singularity (VHS) in Van der Waals materials enhances interaction effects and can host various symmetry breaking and topological phases, including conventional and unconventional superconductivity. While the nature of VHS significantly influences the density of states and susceptibilities, its qualitative impact on experimental observables remains elusive. In our work, we demonstrate that optical absorption spectra in the superconducting state can be utilized to experimentally deduce the VHS fermiology in the normal state. We highlight the optical selection rule imposed by current relaxation and find that the anisotropy of the absorption peak is qualitatively influenced by the number and type of VHS. In this talk, I will discuss the optical selection rule and how it can be employed to distinguish different VHS fermiologies.
Hosted by Prof. Huang