  Strong correlation effects on electron transport through a spinless quantum
dot are considered. When two single-particle levels in the quantum dot are
degenerate, a conserved pseudospin degree of freedom appears for general
tunneling matrix elements between the quantum dot and leads. Local fluctuations
of the pseudospin in the quantum dot give rise to a pair of asymmetric
conductance peaks near the center of a Coulomb valley. An exact relation to the
population switching is provided.
