Mixed-Valence-Driven Heavy-Fermion Behavior and Superconductivity in KNi${}_2$Se${}_2$

Abstract

Based on specific heat and magnetoresistance measurements, we report that a "heavy" electronic state exists below $T\approx$ 20 K in KNi${}_2$Se${}_2$, with an increased carrier mobility and enhanced effective electronic band mass, $m$* = 6$m_b$ to 18$m_b$. This "heavy" state evolves into superconductivity at $T_c$ = 0.80(1) K. These properties resemble that of a many-body heavy-fermion state, which derives from the hybridization between localized magnetic states and conduction electrons. Yet, no evidence for localized magnetism or magnetic order is found in KNi${}_2$Se${}_2$ from magnetization measurements or neutron diffraction. Instead, neutron pair-distribution-function analysis reveals the presence of local charge-density-wave distortions that disappear on cooling, an effect opposite to what is typically observed, suggesting that the low-temperature electronic state of KNi${}_2$Se${}_2$ arises from cooperative Coulomb interactions and proximity to, but avoidance of, charge order.

References in corpus (7)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Giant Anharmonic Phonon Scattering in PbTe
• Unified explanation of the Kadowaki-Woods ratio in strongly correlated materials
• Possible valence-bond condensation in the frustrated cluster magnet LiZn2Mo3O8
• Direct Observation of Quadrupolar Excitons in the Heavy-Fermion Superconductor PrOs${}_4$Sb${}_{12}$
• Metal-Insulator Transition and Orbital Order in PbRuO3
• Stoichiometry, Spin Fluctuations, and Superconductivity in LaNiPO

Cited by in corpus (5)

• Multi-gap nodeless superconductivity in nickel chalcogenide TlNi2Se2
• Lattice dynamics of KNi2Se2
• Electronic tunability of the frustrated triangular-lattice cluster magnet LiZn${}_{2-x}$Mo${}_3$O${}_8$
• Theory of Charge Order and Heavy-Electron Formation in the Mixed-Valence Compound KNi${}_2$Se${}_2$
• The weak electronic correlations and absence of heavy Fermion state in KNi${}_2$Se${}_2$