Abstract
We study the quantum phase transitions in the nickel pnctides, CeNi2−δ(As1−xPx)2 (δ ≈ 0.07–0.22) polycrystalline samples. This series displays the distinct heavy fermion behavior in the rarely studied parameter regime of dilute carrier limit. We systematically investigate the magnetization, specific heat and electrical transport down to low temperatures. Upon increasing the P-content, the antiferromagnetic order of the Ce-4f moment is suppressed continuously and vanishes at xc ~ 0.55. At this doping, the temperature dependences of the specific heat and longitudinal resistivity display non-Fermi liquid behavior. Both the residual resistivity ρ0 and the Sommerfeld coefficient γ0 are sharply peaked around xc. When the P-content reaches close to 100%, we observe a clear low-temperature crossover into the Fermi liquid regime. In contrast to what happens in the parent compound x = 0.0 as a function of pressure, we find a surprising result that the non-Fermi liquid behavior persists over a nonzero range of doping concentration, xc < x < 0.9. In this doping range, at the lowest measured temperatures, the temperature dependence of the specific-heat coefficient is logarithmically divergent and that of the electrical resistivity is linear. We discuss the properties of CeNi2−δ(As1−xPx)2 in comparison with those of its 1111 counterpart, CeNi(As1−xPx)O. Our results indicate a non-Fermi liquid phase in the global phase diagram of heavy fermion metals.
Highlights
As a result of a continuous phase transition at zero temperature, quantum criticality has been broadly discussed in connection with remarkable low temperature properties such as non-Fermi liquid (NFL) and unconventional superconductivity in a number of strongly correlated electron systems[1,2,3]
We discuss the properties of CeNi2−δ(As1−xPx)[2] together with those of its 1111 counterpart, CeNi(As1−xPx)O, and draw implications for the global phase diagram of the heavy fermion metals
CeNi2−δAs2 as a function of hydrostatic pressure[9], here we find a surprising result in the T − x phase diagram of CeNi2−δ(As1−xPx)[2] that the NFL behavior persists over a nonzero range of doping concentration, xc < x < 0.9
Summary
As a result of a continuous phase transition at zero temperature, quantum criticality has been broadly discussed in connection with remarkable low temperature properties such as non-Fermi liquid (NFL) and unconventional superconductivity in a number of strongly correlated electron systems[1,2,3]. The energy scale for the Kondo effect, Kondo temperature TK, depends on the c-f hybridization and the density of states at the Fermi energy, and can be tuned by non-thermal parameters such as external pressure, chemical doping or applied magnetic field, etc This allows to probe a possible QCP by identifying the associated NFL behavior in its vicinity[5,6]. The idea behind this problem is that the collective Kondo screening can still take place in the limit of dilute conduction electrons but with delayed development of coherent paramagnetic Kondo singlet state This scenario has recently been evidenced in the cerium based nickle arsenide, CeNi2−δAs28, where the unconventional quantum criticality has been revealed by tuning the physical pressure[9]. If the Ni vacancies do not change very much under the As/P substitution, we anticipate that CeNi2−δ(As1−xPx)[2] should be a suitable system to investigate whether there is a QCP in a Kondo lattice with a low carrier density
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