Critical Ising modes in low-dimensional Kondo insulators

We present an Ising-like intermediate phase for one-dimensional Kondo insulator systems. Resulting from a spinon splitting, its low-energy excitations are critical Ising modes, whereas the triplet sector has a spectral gap. It should occur as long as the Ruderman-Kittel-Kasuya-Yosida oscillation amplitude dominates over any direct exchange between localized spins. The chiral fixed point, however, becomes unstable in the far-infrared limit due to prevalent fluctuations among localized spins that induce gapless triplet excitations in the spectrum. Based on previous numerical results, we obtain a paramagnetic disordered state ruled by the correlation length of the single impurity Kondo model.