Interview for Faculty Position

Disorder as a window to the (Fermi) sea

Tami Pereg-Barnea

California Institute of Technology

Rather than regarding disorder as an obstacle, in this talk I will show how disorder may be used to extract information about the underlying structure. When the disorder is weak, its effect on the Fermionic sea is to introduce scattering processes. These processes cause interference which leads to spatial modulations in the local density of states. In two dimensions these modulations are accessible by scanning tunneling spectroscopy. Combining the measured local density of states with perturbative calculations enables the extraction of information about the quantum state of the underlying system which is otherwise beyond reach. In addition to mapping the momentum and density of excitations it also reveals their “quantum phase”. Such phase may be, for example, the chirality angle of a Dirac quasiparticle in graphene, the amount of particle-hole mixing in a superconducting state and more. I will present calculations in various systems and compare with measurements whenever possible.