  A Kbar N-pi Sigma-pi Lambda coupled-channel potential is constructed on the
basis of chiral SU(3) dynamics. Several matching conditions are introduced to
formulate an equivalent local potential that reproduces the coupled-channel
scattering amplitudes resulting from chiral SU(3)_L times SU(3)_R meson-baryon
effective field theory. In contrast to a previously constructed effective
single-channel Kbar N potential, the explicit treatment of the pi Sigma channel
yields a natural description of the low-mass pole as part of the two-pole
structure of the Lambda(1405) resonance. The energy dependence of the potential
can now be parametrized with a minimum of polynomial orders. To study the
properties of the Lambda(1405) as a quantum-mechanical quasibound state, we
derive the normalization condition of its wave function generated by the
energy-dependent coupled-channel potential, using the Feshbach projection
method. This framework provides an improved understanding of this system from
the viewpoint of the compositeness of hadrons. With the properly normalized
wave function, we demonstrate and confirm that the high-mass pole of the
Lambda(1405) is dominated by the Kbar N component.
