Quantum critical behavior at the Kondo insulator–non-Fermi liquid boundary for CeRhSb 1−xSn x

Abstract

We have observed a critical behavior at x ⩾ 0.13 for CeRhSb 1− x Sn x , where a transition from Kondo insulator to critical regime for a non-Fermi liquid takes place. The non-Fermi liquid (NFL) state emerges from a moderately heavy Fermi liquid state ( γ ≈ 63 mJ / K 2 mol ) upon cooling. Both the specific heat C/ T and the magnetic susceptibility χ diverge on the metallic side with temperature T → 0 . The divergent character of the susceptibility and the specific heat is attributed to the quantum critical behavior χ = a T - m and C / T = b T - s in the whole metallic (non-Fermi liquid) region; the corresponding critical exponents for x = 0.13 are m = 0.17 and s ≈ 0.3 . The resistivity then diverges logarithmically. On the insulating side, x ⩽ 0.12 , it has been observed that the resistivity scales linearly with χ - 1 in the temperature regime below the coherence peak. On the basis of the experimental results we propose a schematic T– x phase diagram with the quantum critical point (QCP) separating Kondo insulating (KI) and the NFL phases.