Heavy fermion quantum criticality at dilute carrier limit in CeNi$_{2-\delta}$(As$_{1-x}$P$_{x}$)$_{2}$

TL;DR

This study investigates quantum criticality in a heavy fermion series CeNi$_{2- ext{delta}}$(As$_{1-x}$P$_{x}$)$_{2}$, revealing a persistent non-Fermi liquid phase over a range of doping levels near the magnetic quantum critical point.

Contribution

It provides the first detailed exploration of heavy fermion quantum criticality in the dilute carrier limit of CeNi$_{2- ext{delta}}$(As$_{1-x}$P$_{x}$)$_{2}$, highlighting a broad non-Fermi liquid region.

Findings

Antiferromagnetic order vanishes at $x_c \,\sim\, 0.55$

Non-Fermi liquid behavior persists over a doping range $x_c < x < 0.9$

Logarithmic divergence in specific heat and linear resistivity at low temperatures

Abstract

We study the quantum phase transitions in the nickel pnctides, CeNi$_{2-\delta}$(As$_{1-x}$P$_{x}$)$_{2}$ ($\delta$ $\approx$ 0.07-0.22). 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-4$f$ moment is suppressed continuously and vanishes at $x_c \sim$ 0.55. At this doping, the temperature dependences of the specific heat and longitudinal resistivity display non-Fermi liquid behavior. Both the residual resistivity $\rho_0$ and the Sommerfeld coefficient $\gamma_0$ are sharply peaked around $x_c$. 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, $x_c<x<0.9$. 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 CeNi$_{2-\delta}$(As$_{1-x}$P$_{x}$)$_{2}$ in comparison with those of its 1111 counterpart, CeNi(As$_{1-x}$P$_{x}$)O. Our results indicate a non-Fermi liquid phase in the global phase diagram of heavy fermion metals.