We consider the Heisenberg chain of spin 1/2 with a concentration x of impurity spins S. The thermodynamic Bethe ansatz equations are stated for this model. The ground-state equations are analyzed as a function of x and magnetic field. In zero field the ground state is a singlet for finite x, but non-Fermi-liquid-like for x\ensuremath{\rightarrow}0. Two energy bands play a role at T=0. The Van Hove singularities of the empty bands define two critical fields, ${\mathit{H}}_{\mathit{c}1}$ (x) and ${\mathit{H}}_{\mathit{c}2}$ (x), at which the susceptibility diverges. The non-Fermi-liquid behavior as x\ensuremath{\rightarrow}0 arises from nonanalyticities as ${\mathit{H}}_{\mathit{c}2}$ vanishes.We consider the Heisenberg chain of spin 1/2 with a concentration x of impurity spins S. The thermodynamic Bethe ansatz equations are stated for this model. The ground-state equations are analyzed as a function of x and magnetic field. In zero field the ground state is a singlet for finite x, but non-Fermi-liquid-like for x\ensuremath{\rightarrow}0. Two energy bands play a role at T=0. The Van Hove singularities of the empty bands define two critical fields, ${\mathit{H}}_{\mathit{c}1}$(x) and ${\mathit{H}}_{\mathit{c}2}$(x), at which the susceptibility diverges. The non-Fermi-liquid behavior as x\ensuremath{\rightarrow}0 arises from nonanalyticities as ${\mathit{H}}_{\mathit{c}2}$ vanishes.

Physical review. B, Condensed matterApr 1, 199436 citations

{\mathit{H}}_{\mathit{c}1}

(x) and

{\mathit{H}}_{\mathit{c}2}

(x), at which the susceptibility diverges. The non-Fermi-liquid behavior as x\ensuremath{\rightarrow}0 arises from nonanalyticities as

{\mathit{H}}_{\mathit{c}2}

vanishes.