Normal Fermi Surface in the Nodal Superconductor CeCoIn_{5} Revealed via Thermal Conductivity.

The thermal conductivity of heavy-fermion superconductor CeCoIn_{5} was measured with a magnetic field rotating in the tetragonal a-b plane, with the heat current in the antinodal direction, J|| [100]. We observe a sharp resonance in thermal conductivity for the magnetic field at an angle Θ≈12°, measured from the heat current direction [100]. This resonance corresponds to the reported resonance at an angle Θ^{'}≈33° from the direction of the heat current applied along the nodal direction, J||[110].

Light-driven nanoscale vectorial currents.

Controlled charge flows are fundamental to many areas of science and technology, serving as carriers of energy and information, as probes of material properties and dynamics and as a means of revealing or even inducing broken symmetries. Emerging methods for light-based current control offer particularly promising routes beyond the speed and adaptability limitations of conventional voltage-driven systems. However, optical generation and manipulation of currents at nanometre spatial scales remains a basic challenge and a crucial step towards scalable optoelectronic systems for microelectronics and information science.

Microscopic Imaging Homogeneous and Single Phase Superfluid Density in UTe_{2}.

Odd-parity superconductor UTe_{2} shows spontaneous time-reversal symmetry breaking and multiple superconducting phases, which imply chiral superconductivity, but only in a subset of samples. Here we microscopically observe a homogeneous superfluid density n_{s} on the surface of UTe_{2} and an enhanced superconducting transition temperature near the edges. We also detect vortex-antivortex pairs even at zero magnetic field, indicating the existence of a hidden internal field.

Kondo quasiparticle dynamics observed by resonant inelastic x-ray scattering.

Effective models focused on pertinent low-energy degrees of freedom have substantially contributed to our qualitative understanding of quantum materials. An iconic example, the Kondo model, was key to demonstrating that the rich phase diagrams of correlated metals originate from the interplay of localized and itinerant electrons. Modern electronic structure calculations suggest that to achieve quantitative material-specific models, accurate consideration of the crystal field and spin-orbit interactions is imperative.

Temperature dependence of quantum oscillations from non-parabolic dispersions.

The phase offset of quantum oscillations is commonly used to experimentally diagnose topologically nontrivial Fermi surfaces. This methodology, however, is inconclusive for spin-orbit-coupled metals where π-phase-shifts can also arise from non-topological origins. Here, we show that the linear dispersion in topological metals leads to a T-temperature correction to the oscillation frequency that is absent for parabolic dispersions.

Colossal anomalous Nernst effect in a correlated noncentrosymmetric kagome ferromagnet.

The transverse voltage generated by a temperature gradient in a perpendicularly applied magnetic field, termed the Nernst effect, has promise for thermoelectric applications and for probing electronic structure. In magnetic materials, an anomalous Nernst effect (ANE) is possible in a zero magnetic field. We report a colossal ANE in the ferromagnetic metal UCoRuAl, reaching 23 microvolts per kelvin.

Evidence for a pressure-induced antiferromagnetic quantum critical point in intermediate-valence UTe.

UTe is a recently discovered unconventional superconductor that has attracted much interest because of its potentially spin-triplet topological superconductivity. Our ac calorimetry, electrical resistivity, and x-ray absorption study of UTe under applied pressure reveals key insights on the superconducting and magnetic states surrounding pressure-induced quantum criticality at = 1.3 GPa.

Non-monotonic pressure dependence of high-field nematicity and magnetism in CeRhIn.

CeRhIn provides a textbook example of quantum criticality in a heavy fermion system: Pressure suppresses local-moment antiferromagnetic (AFM) order and induces superconductivity in a dome around the associated quantum critical point (QCP) near p ≈ 23 kbar. Strong magnetic fields also suppress the AFM order at a field-induced QCP at B ≈ 50 T. In its vicinity, a nematic phase at B ≈ 28 T characterized by a large in-plane resistivity anisotropy emerges.

Interplay of the Spin Density Wave and a Possible Fulde-Ferrell-Larkin-Ovchinnikov State in CeCoIn_{5} in Rotating Magnetic Field.

The d-wave superconductor CeCoIn_{5} has been proposed as a strong candidate for supporting the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state near the low-temperature boundary of its upper critical field. Neutron diffraction, however, finds spin-density-wave (SDW) order in this part of the phase diagram for field in the a-b plane, and evidence for the SDW disappears as the applied field is rotated toward the tetragonal c axis. It is important to understand the interplay between the SDW and a possible FFLO state in CeCoIn_{5}, as the mere existence of an SDW does not necessarily exclude an FFLO state.

Author Correction: Thermodynamic Signatures of Weyl Fermions in NbP.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Magnetic field-tuned Fermi liquid in a Kondo insulator.

Kondo insulators are expected to transform into metals under a sufficiently strong magnetic field. The closure of the insulating gap stems from the coupling of a magnetic field to the electron spin, yet the required strength of the magnetic field-typically of order 100 T-means that very little is known about this insulator-metal transition. Here we show that Ce[Formula: see text]Bi[Formula: see text]Pd[Formula: see text], owing to its fortuitously small gap, provides an ideal Kondo insulator for this investigation.

Spatial control of heavy-fermion superconductivity in CeIrIn.

Although crystals of strongly correlated metals exhibit a diverse set of electronic ground states, few approaches exist for spatially modulating their properties. In this study, we demonstrate disorder-free control, on the micrometer scale, over the superconducting state in samples of the heavy-fermion superconductor CeIrIn We pattern crystals by focused ion beam milling to tailor the boundary conditions for the elastic deformation upon thermal contraction during cooling. The resulting nonuniform strain fields induce complex patterns of superconductivity, owing to the strong dependence of the transition temperature on the strength and direction of strain.

Quantum Oscillations in Flux-Grown SmB_{6} with Embedded Aluminum.

SmB_{6} is a candidate topological Kondo insulator that displays surface conduction at low temperatures. Here, we perform torque magnetization measurements as a means to detect de Haas-van Alphen (dHvA) oscillations in SmB_{6} crystals grown by aluminum flux. We find that dHvA oscillations occur in single crystals containing embedded aluminum, originating from the flux used to synthesize SmB_{6}.

Enhanced Hybridization Sets the Stage for Electronic Nematicity in CeRhIn_{5}.

High magnetic fields induce a pronounced in-plane electronic anisotropy in the tetragonal antiferromagnetic metal CeRhIn_{5} at H^{*}≳30  T for fields ≃20° off the c axis. Here we investigate the response of the underlying crystal lattice in magnetic fields to 45 T via high-resolution dilatometry. At low fields, a finite magnetic field component in the tetragonal ab plane explicitly breaks the tetragonal (C_{4}) symmetry of the lattice revealing a finite nematic susceptibility.

Thermodynamic Signatures of Weyl Fermions in NbP.

We present a high magnetic field study of NbP-a member of the monopnictide Weyl semimetal (WSM) family. While the monoarsenides (NbAs and TaAs) have topologically distinct left and right-handed Weyl fermi surfaces, NbP is argued to be "topologically trivial" due to the fact that all pairs of Weyl nodes are encompassed by a single Fermi surface. We use torque magnetometry to measure the magnetic response of NbP up to 60 tesla and uncover a Berry paramagnetic response, characteristic of the topological Weyl nodes, across the entire field range.

From Ising Resonant Fluctuations to Static Uniaxial Order in Antiferromagnetic and Weakly Superconducting CeCo(In_{1-x}Hg_{x})_{5}(x=0.01).

CeCo(In_{0.990}Hg_{0.010})_{5} is a charge doped variant of the d-wave CoCoIn_{5} superconductor with coexistent antiferromagnetic and superconducting transitions occurring at T_{N}=3.

Quantum limit transport and destruction of the Weyl nodes in TaAs.

Weyl fermions are a recently discovered ingredient for correlated states of electronic matter. A key difficulty has been that real materials also contain non-Weyl quasiparticles, and disentangling the experimental signatures has proven challenging. Here we use magnetic fields up to 95 T to drive the Weyl semimetal TaAs far into its quantum limit, where only the purely chiral 0th Landau levels of the Weyl fermions are occupied.

Tuning the Pairing Interaction in a d-Wave Superconductor by Paramagnons Injected through Interfaces.

Unconventional superconductivity and magnetism are intertwined on a microscopic level in a wide class of materials. A new approach to this most fundamental and hotly debated issue focuses on the role of interactions between superconducting electrons and bosonic fluctuations at the interface between adjacent layers in heterostructures. Here we fabricate hybrid superlattices consisting of alternating atomic layers of the heavy-fermion superconductor CeCoIn_{5} and antiferromagnetic (AFM) metal CeRhIn_{5}, in which the AFM order can be suppressed by applying pressure.

Spectroscopic evidence for two-gap superconductivity in the quasi-1D chalcogenide NbPdS.

Low-dimensional electronic systems with confined electronic wave functions have attracted interest due to their propensity toward novel quantum phases and their use in wide range of nanotechnologies. The newly discovered chalcogenide NbPdS possesses a quasi-one-dimensional electronic structure and becomes superconducting. Here, we report spectroscopic evidence for two-band superconductivity, where soft point-contact spectroscopic measurements in the superconducting (SC) state reveal Andreev reflection in the differential conductance G.

Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn.

Electronic nematic materials are characterized by a lowered symmetry of the electronic system compared to the underlying lattice, in analogy to the directional alignment without translational order in nematic liquid crystals. Such nematic phases appear in the copper- and iron-based high-temperature superconductors, and their role in establishing superconductivity remains an open question. Nematicity may take an active part, cooperating or competing with superconductivity, or may appear accidentally in such systems.

Inducing superconductivity in Weyl semimetal microstructures by selective ion sputtering.

By introducing a superconducting gap in Weyl or Dirac semimetals, the superconducting state inherits the nontrivial topology of their electronic structure. As a result, Weyl superconductors are expected to host exotic phenomena, such as nonzero-momentum pairing due to their chiral node structure, or zero-energy Majorana modes at the surface. These are of fundamental interest to improve our understanding of correlated topological systems, and, moreover, practical applications in phase-coherent devices and quantum applications have been proposed.

Resonances in the Field-Angle-Resolved Thermal Conductivity of CeCoIn_{5}.

The thermal conductivity measurement in a rotating magnetic field is a powerful probe of the structure of the superconducting energy gap. We present high-precision measurements of the low-temperature thermal conductivity in the unconventional heavy-fermion superconductor CeCoIn_{5}, with the heat current J along the nodal [110] direction of its d_{x^{2}-y^{2}} order parameter and the magnetic field up to 7 T rotating in the ab plane. In contrast to the smooth oscillations found previously for J∥[100], we observe a sharp resonancelike peak in the thermal conductivity when the magnetic field is also in the [110] direction, parallel to the heat current.