Field-Induced Quantum Critical Point inCeCoIn5

Abstract

The resistivity of the heavy-fermion superconductor CeCoIn5 was measured as a function of temperature, down to 25 mK and in magnetic fields of up to 16 T applied perpendicular to the basal plane. With increasing field, we observe a suppression of the non-Fermi liquid behavior, rho approximately T, and the development of a Fermi liquid state, with its characteristic rho=rho(0)+AT2 dependence. The field dependence of the T2 coefficient shows critical behavior with an exponent of 1.37. This is evidence for a field-induced quantum critical point (QCP), occurring at a critical field which coincides, within experimental accuracy, with the superconducting critical field H(c2). We discuss the relation of this field-tuned QCP to a change in the magnetic state, seen as a change in magnetoresistance from positive to negative, at a crossover line that has a common border with the superconducting region below approximately 1 K.

Superconductivity and Non-Fermi-Liquid Behavior in the Heavy-Fermion Compound CeCo1−xNixIn5

“…35) It is known that ρ(T ) between T c and T max for CeCoIn 5 exhibits the NFL behavior with the T -linear dependence. 6,20) A similar NFL behavior is also seen in the Ni substitutions. The exponent n of the T n function in ρ(T ), obtained by simply fitting the ρ(T ) data between 2.5 and 15 K, decreases to 0.65(5) at x = 0.125, but then recovers to 0.85(4) at x = 0.25 and 1.00(5) at x = 0.30 (2) [lower inset of Fig.…”

“…[13][14][15][16][17][18] Furthermore, the existence of the AFM-QCP at ∼ H c2 is strongly suggested from the observations of the NFL behavior in the paramagnetic phase above H c2 , including the − ln T divergence in specific heat divided by temperature, the T -linear dependence in magnetization, and electrical resistivity. 10,19,20) In fact, the long-range AFM orders are generated by substituting the ions for the elements in CeCoIn 5 , such as Nd for Ce, 21,22) Rh for Co, [23][24][25][26] and Cd, Hg, and Zn for In. [27][28][29][30] In contrast to the doping effect by those ions, the substitution of Sn for In simply suppresses the SC phase without generating the AFM order.…”

New hints on the origin of quantum criticality in CeCoIn5: A Hall effect study

“…In the unusual case of CeCoIn 5 [7], however, a magnetic field tuned QCP [8] is suggested. The corresponding critical field coincides with H c2 in the H-T phase diagram at ambient pressure [5][6][7]9]. The pressure evolution implies that this coincidence is accidental and that the origin of the QCP is not SC [10].…”

Erratum: Coherence in molecular nitrogen

“…1), not a magnetic QCP. Note, however, that it would not be the fi rst time that a magnetic QCP is avoided in favour of superconductivity 8,9 .…”