Connection between -electron correlations and magnetic excitations in UTe.

The detailed anisotropic dispersion of the low-temperature, low-energy magnetic excitations of the candidate spin-triplet superconductor UTe is revealed using inelastic neutron scattering. The magnetic excitations emerge from the Brillouin zone boundary at the high symmetry and points and disperse along the crystallographic -axis. In applied magnetic fields to at least = 11 T along the , the magnetism is found to be field-independent in the ( 0) plane.

Inhomogeneous high temperature melting and decoupling of charge density waves in spin-triplet superconductor UTe.

Charge, spin and Cooper-pair density waves have now been widely detected in exotic superconductors. Understanding how these density waves emerge - and become suppressed by external parameters - is a key research direction in condensed matter physics. Here we study the temperature and magnetic-field evolution of charge density waves in the rare spin-triplet superconductor candidate UTe using scanning tunneling microscopy/spectroscopy.

Skyrmion lattice formation and destruction mechanisms probed with TR-SANS.

Magnetic skyrmions are topologically protected, nanoscale whirls of the spin configuration that tend to form hexagonally ordered arrays. As a topologically non-trivial structure, the nucleation and annihilation of the skyrmion, as well as the interaction between skyrmions, varies from conventional magnetic systems. Recent works have suggested that the ordering kinetics in these materials occur over millisecond or longer timescales, which is unusually slow for magnetic dynamics.

Orphan high field superconductivity in non-superconducting uranium ditelluride.

Reentrant superconductivity is an uncommon phenomenon in which the destructive effects of magnetic field on superconductivity are mitigated, allowing a zero-resistance state to survive under conditions that would otherwise destroy it. Typically, the reentrant superconducting region derives from a zero-field parent superconducting phase. Here, we show that in UTe crystals extreme applied magnetic fields give rise to an unprecedented high-field superconductor that lacks a zero-field antecedent.

Resonant Ultrasound Spectroscopy for Irregularly Shaped Samples and Its Application to Uranium Ditelluride.

Resonant ultrasound spectroscopy (RUS) is a powerful technique for measuring the full elastic tensor of a given material in a single experiment. Previously, this technique was practically limited to regularly shaped samples such as rectangular parallelepipeds, spheres, and cylinders [W. M.

A review of UTeat high magnetic fields.

Uranium ditelluride (UTe) is recognized as a host material to unconventional spin-triplet superconductivity, but it also exhibits a wealth of additional unusual behavior at high magnetic fields. One of the most prominent signatures of the unconventional superconductivity is a large and anisotropic upper critical field that exceeds the paramagnetic limit. This superconductivity survives to 35 T and is bounded by a discontinuous magnetic transition, which itself is also field-direction-dependent.

Detection of a pair density wave state in UTe.

Spin-triplet topological superconductors should exhibit many unprecedented electronic properties, including fractionalized electronic states relevant to quantum information processing. Although UTe may embody such bulk topological superconductivity, its superconductive order parameter Δ(k) remains unknown. Many diverse forms for Δ(k) are physically possible in such heavy fermion materials.

CHESS: The future direct geometry spectrometer at the second target station.

CHESS, chopper spectrometer examining small samples, is a planned direct geometry neutron chopper spectrometer designed to detect and analyze weak signals intrinsic to small cross sections (e.g., small mass, small magnetic moments, or neutron absorbing materials) in powders, liquids, and crystals.

Non-magnetic ion site disorder effects on the quantum magnetism of a spin-1/2 equilateral triangular lattice antiferromagnet.

With the motivation to study how non-magnetic ion site disorder affects the quantum magnetism of BaCoSbO, a spin-1/2 equilateral triangular lattice antiferromagnet, we performed DC and AC susceptibility, specific heat, elastic and inelastic neutron scattering measurements on single crystalline samples of BaSrCoSbOwith Sr doping on non-magnetic Baion sites. The results show that BaSrCoSbOexhibits (i) a two-step magnetic transition at 2.7 K and 3.

Multicomponent superconducting order parameter in UTe.

An unconventional superconducting state was recently discovered in uranium ditelluride (UTe), in which spin-triplet superconductivity emerges from the paramagnetic normal state of a heavy-fermion material. The coexistence of magnetic fluctuations and superconductivity, together with the crystal structure of this material, suggests that a distinctive set of symmetries, magnetic properties, and topology underlie the superconducting state. Here, we report observations of a nonzero polar Kerr effect and of two transitions in the specific heat upon entering the superconducting state, which together suggest that the superconductivity in UTe is characterized by a two-component order parameter that breaks time-reversal symmetry.

Comparison of Two Different Synthesis Methods of Single Crystals of Superconducting Uranium Ditelluride.

Single crystal specimens of the actinide compound uranium ditelluride, UTe2, are of great importance to the study and characterization of its dramatic unconventional superconductivity, believed to entail spin-triplet electron pairing. A variety in the superconducting properties of UTe2 reported in the literature indicates that discrepancies between synthesis methods yield crystals with different superconducting properties, including the absence of superconductivity entirely. This protocol describes a process to synthesize crystals that exhibit superconductivity via chemical vapor transport, which has consistently exhibited a superconducting critical temperature of 1.

Magnetic ordering in the Ising antiferromagnetic pyrochlore NdScNbO.

The question of structural disorder and its effects on magnetism is relevant to a number of spin liquid candidate materials. Although commonly thought of as a route to spin glass behaviour, here we describe a system in which the structural disorder results in long-range antiferromagnetic order due to local symmetry breaking. NdScNbOis shown to have a dispersionless gapped excitation observed in other neodymium pyrochlores below= 0.

Van Hove singularity in the magnon spectrum of the antiferromagnetic quantum honeycomb lattice.

In quantum magnets, magnetic moments fluctuate heavily and are strongly entangled with each other, a fundamental distinction from classical magnetism. Here, with inelastic neutron scattering measurements, we probe the spin correlations of the honeycomb lattice quantum magnet YbCl. A linear spin wave theory with a single Heisenberg interaction on the honeycomb lattice, including both transverse and longitudinal channels of the neutron response, reproduces all of the key features in the spectrum.

Frustrated Heisenberg model within the stretched diamond lattice of LiYbO.

We investigate the magnetic properties of LiYbO, containing a three-dimensionally frustrated, diamond-like lattice via neutron scattering, magnetization, and heat capacity measurements. The stretched diamond network of Yb ions in LiYbO enters a long-range incommensurate, helical state with an ordering wave vector that "locks-in" to a commensurate phase under the application of a magnetic field. The spiral magnetic ground state of LiYbO can be understood in the framework of a Heisenberg Hamiltonian on a stretched diamond lattice, where the propagation vector of the spiral is uniquely determined by the ratio of .

Topologically driven linear magnetoresistance in helimagnetic FeP.

The helimagnet FeP is part of a family of binary pnictide materials with the MnP-type structure, which share a nonsymmorphic crystal symmetry that preserves generic band structure characteristics through changes in elemental composition. It shows many similarities, including in its magnetic order, to isostructural CrAs and MnP, two compounds that are driven to superconductivity under applied pressure. Here we present a series of high magnetic field experiments on high-quality single crystals of FeP, showing that the resistance not only increases without saturation by up to several hundred times its zero-field value by 35 T, but that it also exhibits an anomalously linear field dependence over the entire range when the field is aligned precisely along the crystallographic c-axis.

Effect of chemical substitution on the skyrmion phase in CuOSeO.

Magnetic skyrmions have been the focus of intense research due to their unique qualities which result from their topological protections. Previous work on CuOSeO, the only known insulating multiferroic skyrmion material, has shown that chemical substitution alters the skyrmion phase. We chemically substitute Zn, Ag, and S into powdered CuOSeO to study the effect on the magnetic phase diagram.

Low-temperature crystal structure of the unconventional spin-triplet superconductor UTe from single-crystal neutron diffraction.

The crystal structure of a new superconductor UTe has been investigated using single-crystal neutron diffraction for the first time at the low temperature (LT) of 2.7 K, just above the superconducting transition temperature of ∼1.6 K, in order to clarify whether the orthorhombic structure of type Immm (No.

Quantum Versus Classical Spin Fragmentation in Dipolar Kagome Ice HoMgSbO.

A promising route to realize entangled magnetic states combines geometrical frustration with quantum-tunneling effects. Spin-ice materials are canonical examples of frustration, and Ising spins in a transverse magnetic field are the simplest many-body model of quantum tunneling. Here, we show that the tripod-kagome lattice material HoMgSbO unites an icelike magnetic degeneracy with quantum-tunneling terms generated by an intrinsic splitting of the Ho ground-state doublet, which is further coupled to a nuclear spin bath.

Three-dimensional magnetism and the Dzyaloshinskii-Moriya interaction in = 3/2 kagome staircase CoVO.

Time-of-flight neutron data reveal spin waves in the ferromagnetic ground state of the kagome staircase material CoVO. While previous work has treated this material as quasi-two-dimensional, we find that an inherently three-dimensional description is needed to describe the spin wave spectrum throughout reciprocal space. Moreover, spin wave branches show gaps that point to an unexpectedly large Dzyaloshinskii-Moriya interaction on the nearest-neighbor bond, with ≥ /2.

Enhancement and reentrance of spin triplet superconductivity in UTe under pressure.

Spin triplet superconductivity in the Kondo lattice UTe appears to be associated with spin fluctuations originating from incipient ferromagnetic order. Here we show clear evidence of twofold enhancement of superconductivity under pressure, which discontinuously transitions to magnetic order, likely of ferromagnetic nature, at higher pressures. The application of a magnetic field tunes the system back across a first-order phase boundary.

Chiral superconductivity in heavy-fermion metal UTe.

Spin-triplet superconductors are condensates of electron pairs with spin 1 and an odd-parity wavefunction. An interesting manifestation of triplet pairing is the chiral p-wave state, which is topologically non-trivial and provides a natural platform for realizing Majorana edge modes. However, triplet pairing is rare in solid-state systems and has not been unambiguously identified in any bulk compound so far.

Low Energy Band Structure and Symmetries of UTe_{2} from Angle-Resolved Photoemission Spectroscopy.

The compound UTe_{2} has recently been shown to realize spin triplet superconductivity from a nonmagnetic normal state. This has sparked intense research activity, including theoretical analyses that suggest the superconducting order parameter to be topologically nontrivial. However, the underlying electronic band structure is a critical factor for these analyses, and remains poorly understood.

Quasi-Two-Dimensional Magnon Identification in Antiferromagnetic FePS Magneto-Raman Spectroscopy.

Recently it was discovered that van der Waals-bonded magnetic materials retain long range magnetic ordering down to a single layer, opening many avenues in fundamental physics and potential applications of these fascinating materials. One such material is FePS, a large spin (S=2) Mott insulator where the Fe atoms form a honeycomb lattice. In the bulk, FePS has been shown to be a quasi-two-dimensional-Ising antiferromagnet, with additional features in the Raman spectra emerging below the Néel temperature () of approximately 120 K.