Multichannel Kondo effect in an interacting electron system: Exact results for the low-temperature thermodynamics

We study the low-temperature thermodynamics of a spin-S magnetic impurity coupled to m>2 degenerate bands of interacting electrons in one dimension. By exploiting boundary-conformal-field-theory techniques, we derive exact results for the possible impurity thermal and magnetic response. The leading behavior of the impurity magnetic susceptibility is shown to be insensitive to the electron-electron interaction. In contrast, there are two types of scaling behavior of the impurity specific heat consistent with the symmetries of the problem: Either it remains the same as for the ordinary multichannel Kondo problem for noninteracting electrons or it acquires a new leading term governed by a critical exponent am5(gm 21)/m , where gm<1 is a generalized ~m channel! Luttinger-liquid charge parameter measuring the strength of the repulsive electronelectron interaction. We conjecture that the latter behavior is indeed realized when the impurity is exactly screened (m52S). @S0163-1829~98!05002-4#