Field-induced compensation of magnetic exchange as the possible origin of reentrant superconductivity in UTe.

The potential spin-triplet heavy-fermion superconductor UTe exhibits signatures of multiple distinct superconducting phases. For field aligned along the b axis, a metamagnetic transition occurs at μH ≈ 35 T. It is associated with magnetic fluctuations that may be beneficial for the field-reinforced superconductivity surviving up to H.

Unveiling the double-peak structure of quantum oscillations in the specific heat.

Quantum oscillation phenomenon is an essential tool to understand the electronic structure of quantum matter. Here we report a systematic study of quantum oscillations in the electronic specific heat C in natural graphite. We show that the crossing of a single spin Landau level and the Fermi energy give rise to a double-peak structure, in striking contrast to the single peak expected from Lifshitz-Kosevich theory.

Quantum-well states at the surface of a heavy-fermion superconductor.

Two-dimensional electronic states at surfaces are often observed in simple wide-band metals such as Cu or Ag (refs. ). Confinement by closed geometries at the nanometre scale, such as surface terraces, leads to quantized energy levels formed from the surface band, in stark contrast to the continuous energy dependence of bulk electron bands.

Dimensionality Driven Enhancement of Ferromagnetic Superconductivity in URhGe.

In most unconventional superconductors, like the high-T_{c} cuprates, iron pnictides, or heavy-fermion systems, superconductivity emerges in the proximity of an electronic instability. Identifying unambiguously the pairing mechanism remains nevertheless an enormous challenge. Among these systems, the orthorhombic uranium ferromagnetic superconductors have a unique position, notably because magnetic fields couple directly to ferromagnetic order, leading to the fascinating discovery of the reemergence of superconductivity in URhGe at a high field.

Field-induced magnetic instability within a superconducting condensate.

The application of magnetic fields, chemical substitution, or hydrostatic pressure to strongly correlated electron materials can stabilize electronic phases with different organizational principles. We present evidence for a field-induced quantum phase transition, in superconducting NdCeCoIn, that separates two antiferromagnetic phases with identical magnetic symmetry. At zero field, we find a spin-density wave that is suppressed at the critical field μ* = 8 T.

Lifshitz Transitions in the Ferromagnetic Superconductor UCoGe.

We present high field magnetoresistance, Hall effect and thermopower measurements in the Ising-type ferromagnetic superconductor UCoGe. A magnetic field is applied along the easy magnetization c axis of the orthorhombic crystal. In the different experimental probes, we observed five successive anomalies at H≈4, 9, 12, 16, and 21 T.