title: Characteristic signatures of quantum criticality driven by geometrical frustration.
abstract: Geometrical frustration describes situations where interactions are incompatible with the lattice geometry and stabilizes exotic phases such as spin liquids. Whether geometrical frustration of magnetic interactions in metals can induce unconventional quantum critical points is an active area of research. We focus on the hexagonal heavy fermion metal CeRhSn, where the Kondo ions are located on distorted kagome planes stacked along the c axis. Low-temperature specific heat, thermal expansion, and magnetic Grüneisen parameter measurements prove a zero-field quantum critical point. The linear thermal expansion, which measures the initial uniaxial pressure derivative of the entropy, displays a striking anisotropy. Critical and noncritical behaviors along and perpendicular to the kagome planes, respectively, prove that quantum criticality is driven be geometrical frustration. We also discovered a spin flop-type metamagnetic crossover. This excludes an itinerant scenario and suggests that quantum criticality is related to local moments in a spin liquid-like state.
authors.affiliation: I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Tokiwa
authors.affiliation: I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany. ; Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Stingl
authors.affiliation: Department of Quantum Matter, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima 739-8530, Japan.
authors.forename: Moo-Sung
authors.initials: MS
authors.lastname: Kim
authors.affiliation: Department of Quantum Matter, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima 739-8530, Japan.
authors.forename: Toshiro
authors.initials: T
authors.lastname: Takabatake
authors.affiliation: I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany. ; Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Gegenwart
keywords: Non-Fermi liquid; Quantum Critical Point; geometrical frustration; heavy fermion system; spin liquid; thermal expansion,specific heat