Kondo destruction in a quantum paramagnet with magnetic frustration

This is the authors' abstract. We don't add key points for this paper.

We report results of isothermal magnetotransport and susceptibility measurements at elevated magnetic fields B down to very low temperatures T on single crystals of the frustrated Kondo-lattice system CePdAl. They reveal a B*(T) line within the paramagnetic part of the phase diagram. This line denotes a thermally broadened ``small''--to-``large'' Fermi-surface crossover which substantially narrows upon cooling. At B₀*=B*(T=0)=(4.6±0.1)T, this B*(T) line merges with two other crossover lines, viz. Tₚ(B) below and TFL(B) above B₀*. Tₚ characterizes a frustration-dominated spin-liquid state, while TFL is the Fermi-liquid temperature associated with the lattice Kondo effect. Non-Fermi-liquid phenomena which are commonly observed near a ``Kondo-destruction'' quantum-critical point cannot be resolved in CePdAl. Our observations reveal a rare case where Kondo coupling, frustration, and quantum criticality are closely intertwined.