title: Gradient catastrophe and Fermi-edge resonances in Fermi gas.
abstract: Any smooth spatial disturbance of a degenerate Fermi gas inevitably becomes sharp. This phenomenon, called the gradient catastrophe, causes the breakdown of a Fermi sea to multiconnected components characterized by multiple Fermi points. We argue that the gradient catastrophe can be probed through a Fermi-edge singularity measurement. In the regime of the gradient catastrophe the Fermi-edge singularity problem becomes a nonequilibrium and nonstationary phenomenon. We show that the gradient catastrophe transforms the single-peaked Fermi-edge singularity of the tunneling (or absorption) spectrum to a sequence of multiple asymmetric singular resonances. An extension of the bosonic representation of the electronic operator to nonequilibrium states captures the singular behavior of the resonances.
authors: Racah Institute of Physics, Hebrew University, Jerusalem, Israel.
authors: E
authors: E
authors: Bettelheim
authors: Y
authors: Y
authors: Kaplan
authors: P
authors: P
authors: Wiegmann