Collective modes and electronic spectral function in smooth edges of quantum hall systems

We present a microscopic theory of the collective modes of a ``smooth'' edge of a quantum Hall system, showing under what conditions these modes can be described as a set of independent bosons. We then calculate the electronic spectral function in an independent-boson model---a procedure that reduces to standard bosonization in the limit of ``sharp'' edge. The I-V tunneling characteristics deduced from this model exhibit, for low voltage, a power-law behavior, with exponents that differ significantly from those of the sharp edge model. {} 1996 The American Physical Society.