The Joint Condensed Matter Seminar (JCMS) series is organised by KTH Royal Insitute of Technology, Nordita, and Stockholm University.
On Thursday, June 1st, 2023 from 10 am to 11 am we will host a seminar by Marcus Stålhammar from Nordita.
Fractal nodal band structures and Fermi surfaces
The studies of fractal lines and surfaces comprise a promising venue within complex dynamics and topology, with profound applications in various venues in physics. Here, condensed matter physics comprise one example, where factuality marks a transition between the ergodic and localized phase. On the other hand, recent years have marked a paradigm shift within physics research as non-effective Hamiltonians have gained vastly increased attention. This has lead to the discovery of numerous novel and uniquely non-Hermitian topological phenomena, many of which are related to the ubiquitous appearance of exceptional points where both eigenvalues and eigenvectors coalesce, leaving the parent Hamiltonian defective.
In this talk, I merge these two concepts by illustrating the appearance of fractal lines of exceptional points and fractal Fermi surfaces in 2D non-Hermitian systems subject to parity-time symmetry. I also show how the notion of factuality can be generalized to 3D by considering various setups, both in the Hermitian and the non-Hermitian realms, and how the presence/absence of parity-time symmetry affects the systems. These results are of experimental relevance within a wide range of different areas of physics, which I will briefly discuss, and might thus have interesting applications on the physics of Fermi surface instability driven phenomena, such as superconductivity and charge-density waves, but also in the context of analogue gravity and black hole physics.