Non-Fermi liquid regimes with and without quantum criticality in Ce^sub 1-x^Yb^sub x^CoIn^sub 5

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 18; p. 7160
• Main Authors: Hu, Tao, Singh, Yogesh P, Shu, Lei, Janoschek, Marc, Dzero, Maxim, Maple, M Brian, Almasan, Carmen C
• Format: Journal Article
• Language: English
• Published: Washington National Academy of Sciences 30-04-2013
• Subjects: Correlation analysis; Magnetic fields; Phase transitions; Superconductivity; Thermodynamics
• ISSN: 0027-8424; 1091-6490

One of the greatest challenges to Landau's Fermi liquid theory -- the standard theory of metals -- is presented by complex materials with strong electronic correlations. In these materials, non-Fermi liquid transport and thermodynamic properties are often explained by the presence of a continuous quantum phase transition that happens at a quantum critical point (QCP). A QCP can be revealed by applying pressure, magnetic field, or changing the chemical composition. In the heavy-fermion compound CeCoIn5, the QCP is assumed to play a decisive role in defining the microscopic structure of both normal and superconducting states. However, the question of whether a QCP must be present in the material's phase diagram to induce non-Fermi liquid behavior and trigger superconductivity remains open. Here, we show that the full suppression of the field-induced QCP in CeCoIn5 by doping with Yb has surprisingly little impact on both unconventional superconductivity and non-Fermi liquid behavior. This implies that the non-Fermi liquid metallic behavior could be a new state of matter in its own right rather than a consequence of the underlying quantum phase transition. [PUBLICATION ABSTRACT]