Wydarzenia

Seminarium Instytutu Fizyki Teoretycznej Uniwersytetu Wrocławskiego

Fractional skyrmions in quantum Hall systems

prof. dr hab. inż. Arkadiusz Wójs

Politechnika Wrocławska

The talk will review the physics of skyrmions formed in ferromagnetic quantum Hall states of two-dimensional electrons in a high magnetic field. Skyrmions carry electric charge, angular momentum, and massive spin, and their emergence as lowest energy charged quasiparticles in a ferromagnetic ground state causes its spin depolarization. It also supports spin-flip excitations with energies below the single-electron spin splitting which can be probed by spectroscopy. Skyrmions have also been predicted in ferromagnetic fractional quantum Hall (FQH) systems, such as Laughlin incompressible liquid at the Landau level filling factor ν=1/3. Understanding of the FQH effect involves a variety of exotic emergent topological particles, such as fractionally charged quasiparticles, composite fermions (CFs), nonabelian anyons, or Majorana fermions. In particular, the incompressibility and the nature of excitation spectrum of the many known FQH ground states is underlied by the formation of essentially free CFs from strongly correlated electrons – through binding of pairs of quantized vortices of the many-electron wave-function as a result of Coulomb interaction within a degenerate Landau level. As fractional quantum Hall states of electrons correspond to integral quantum Hall states of CFs, so do fractional skyrmions emerge as topological spin textures in the CF ferromagnets.