Merging of single-particle levels in finite Fermi systems
V. A. Khodel +*, J. W. Clark *, Haochen Li *, M. V. Zverev +
+Russian Research Centre Kurchatov Institute, 123182 Moscow, Russia
*McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130, USA
PACS: 21.10.-k, 21.60.-n, 36.20.Kd
Abstract
Properties of the distribution of single-particle levels adjacent
to the Fermi surface in finite Fermi systems are studied, focusing
on the case in which these levels are degenerate. The
interaction of the quasiparticles occupying these levels lifts
the degeneracy and affects the distance between the closest
levels on opposite sides of the Fermi surface, as the number
of particles in the system is varied. In addition to the familiar
scenario of level crossing, a new phenomenon is uncovered,
in which the merging of single-particle levels results in
the disappearance of well-defined single-particle excitations.
Implications of this finding are discussed for nuclear, solid-state,
and atomic systems.