Pressure-tuned quantum criticality in the antiferromagnetic Kondo semimetal CeNi2−δAs2

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 44; pp. 13520 - 13524
• Main Authors: Luo, Yongkang, Ronning, F, Wakeham, N, Lu, Xin, Park, Tuson, Xu, Z-A, Thompson, J D
• Format: Journal Article
• Language: English
• Published: United States National Acad Sciences 03.11.2015; National Academy of Sciences, Washington, DC (United States); National Academy of Sciences
• Subjects: anomalous Hall effect; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; heavy Fermion; Kondo effect; MATERIALS SCIENCE; Nozieres exhaustion; Physical Sciences; quantum criticality; quantum criticality; anomalous Hall effect; Kondo effect; Nozières exhaustion; heavy Fermion
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1509581112

The easily tuned balance among competing interactions in Kondo-lattice metals allows access to a zero-temperature, continuous transition between magnetically ordered and disordered phases, a quantum-critical point (QCP). Indeed, these highly correlated electron materials are prototypes for discovering and exploring quantum-critical states. Theoretical models proposed to account for the strange thermodynamic and electrical transport properties that emerge around the QCP of a Kondo lattice assume the presence of an indefinitely large number of itinerant charge carriers. Here, we report a systematic transport and thermodynamic investigation of the Kondo-lattice system CeNi2-δAs2 (δ ≈ 0.28) as its antiferromagnetic order is tuned by pressure and magnetic field to zero-temperature boundaries. These experiments show that the very small but finite carrier density of ~0.032 E-/formular unit in CeNi2-δAs2 leads to unexpected transport signatures of quantum criticality and the delayed development of a fully coherent Kondo-lattice state with decreasing temperature. The small carrier density and associated semimetallicity of this Kondo-lattice material favor an unconventional, local-moment type of quantum criticality and raises the specter of the Nozières exhaustion idea that an insufficient number of conduction-electron spins to separately screen local moments requires collective Kondo screening.