Localized 4f-electrons in the quantum critical heavy fermion ferromagnet CeRhGe.

Ferromagnetic quantum critical points were predicted to be prohibited in clean itinerant ferromagnetic systems, yet such a phenomenon was recently revealed in CeRhGe, where the Curie temperature can be continuously suppressed to zero under a moderate hydrostatic pressure. Here we report the observation of quantum oscillations in CeRhGe from measurements using the cantilever and tunnel-diode oscillator methods in fields up to 45 T, clearly demonstrating that the ferromagnetic quantum criticality occurs in a clean system. In order to map the Fermi surface of CeRhGe, we performed angle-dependent measurements of quantum oscillations at ambient pressure, and compared the results to density functional theory calculations.

Anisotropic c-f Hybridization in the Ferromagnetic Quantum Critical Metal CeRh_{6}Ge_{4}.

Heavy fermion compounds exhibiting a ferromagnetic quantum critical point have attracted considerable interest. Common to two known cases, i.e.

Recent progress on superconductors with time-reversal symmetry breaking.

Superconductivity and magnetism are adversarial states of matter. The presence of spontaneous magnetic fields inside the superconducting state is, therefore, an intriguing phenomenon prompting extensive experimental and theoretical research. In this review, we discuss recent experimental discoveries of unconventional superconductors which spontaneously break time-reversal symmetry and theoretical efforts in understanding their properties.

Strange-metal behaviour in a pure ferromagnetic Kondo lattice.

A wide range of metals exhibit anomalous electrical and thermodynamic properties when tuned to a quantum critical point (QCP), although the origins of such strange metals have posed a long-standing mystery. The frequent association of strange metals with unconventional superconductivity and antiferromagnetic QCPs has led to the belief that they are highly entangled quantum states. By contrast, ferromagnets are regarded as an unlikely setting for strange metals, because they are weakly entangled and their QCPs are often interrupted by competing phases or first-order phase transitions.

Physical properties and field-induced metamagnetic transitions in UAuSb.

We have successfully synthesized single crystals of UAuSb using a flux method and present a comprehensive study of its physical properties by measuring the magnetic susceptibility, electrical resistivity and specific heat. Evidence for at least three magnetic phases is observed in the field-temperature phase diagram of UAuSb. In zero field, the system undergoes an antiferromagnetic transition at 71 K, and upon further cooling it passes through another antiferromagnetic phase with a ferromagnetic component, before reaching a ferromagnetic ground state.

Fully gapped -wave superconductivity in CeCuSi.

The nature of the pairing symmetry of the first heavy fermion superconductor CeCuSi has recently become the subject of controversy. While CeCuSi was generally believed to be a d-wave superconductor, recent low-temperature specific heat measurements showed evidence for fully gapped superconductivity, contrary to the nodal behavior inferred from earlier results. Here, we report London penetration depth measurements, which also reveal fully gapped behavior at very low temperatures.

Evidence for nodal superconductivity in a layered compound TaPdTe.

We report an investigation of the London penetration depth [Formula: see text] on single crystals of the layered superconductor TaPdTe, where the crystal structure has quasi-one-dimensional characteristics. A linear temperature dependence of [Formula: see text] is observed for [Formula: see text], in contrast to the exponential behavior of fully gapped superconductors. This indicates the existence of line nodes in the superconducting energy gap.