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The unconventional superconductor UTe2 exhibits numerous signatures of spin-triplet superconductivity--a rare state of matter which could enable quantum computation protected against decoherence. UTe2 possesses a complex phase landscape comprising two magnetic field-induced superconducting phases, a metamagnetic transition to a field-polarized state, along with pair- and charge-density wave orders. However, contradictory reports between studies performed on UTe2 specimens of varying quality have severely impeded theoretical efforts to understand the microscopic origins of the exotic superconductivity. Here, we report a comprehensive suite of high magnetic field measurements on a generation of pristine quality UTe2 crystals. Our experiments reveal a significantly revised high magnetic field superconducting phase diagram in the ultraclean limit, showing a pronounced sensitivity of field-induced superconductivity to the presence of crystalline disorder. We employ a Ginzburg-Landau model that excellently captures this acute dependence on sample quality. Our results suggest that in close proximity to a field-induced metamagnetic transition the enhanced role of magnetic fluctuations--that are strongly suppressed by disorder--is likely responsible for tuning UTe2 between two distinct spin-triplet superconducting phases. [ABSTRACT FROM AUTHOR]

The heavy fermion paramagnet UTe2 exhibits numerous characteristics of spin-triplet superconductivity. Efforts to understand the microscopic details of this exotic superconductivity have been impeded by uncertainty regarding the underlying electronic structure. Here we directly probe the Fermi surface of UTe2 by measuring magnetic quantum oscillations in pristine quality crystals. We find an angular profile of quantum oscillatory frequency and amplitude that is characteristic of a quasi-2D Fermi surface, which we find is well described by two cylindrical Fermi sheets of electron- and hole-type respectively. Additionally, we find that both cylindrical Fermi sheets possess considerable undulation but negligible small-scale corrugation, which may allow for their near-nesting and therefore promote magnetic fluctuations that enhance the triplet pairing mechanism. Importantly, we find no evidence for the presence of any 3D Fermi surface sections. Our results place strong constraints on the possible symmetry of the superconducting order parameter in UTe2. A. G. Eaton et al. directly probe the Fermi surface of the candidate triplet superconductor UTe2 by measuring magnetic quantum oscillations in ultra-pure crystals. By comparison with model calculations, the data are found to be consistent with a Fermi surface that consists of two cylindrical sections of electron and hole-type respectively. [ABSTRACT FROM AUTHOR]

Homojunctions between Bi2Se3 and its Mn-doped phase are investigated as a sample geometry to study the influence of spin degrees of freedom on topological insulator properties. n quintuple layers of Bi2Se3 are grown on top of Mn-doped Bi2Se3 by molecular beam epitaxy for 0 ≤ n ≤ 30QLs, allowing to unhamperedly monitor the development of electronic and topological properties by surface sensitive techniques like angle resolved photoemission spectroscopy. With increasing n, a Mninduced gap at the Dirac point is gradually filled in an "hourglass" fashion to reestablish a topological surface state at n ∼ 9QLs. Our results suggest a competition of upward and downward band bending effects due to the presence of an n-p type interface, which can be used to tailor topological and quantum well states independently. [ABSTRACT FROM AUTHOR]

The unconventional superconductor UTe2 exhibits numerous signatures of spin-triplet superconductivity--a rare state of matter which could enable quantum computation protected against decoherence. UTe2 possesses a complex phase landscape comprising two magnetic field-induced superconducting phases, a metamagnetic transition to a field-polarized state, along with pair- and charge-density wave orders. However, contradictory reports between studies performed on UTe2 specimens of varying quality have severely impeded theoretical efforts to understand the microscopic origins of the exotic superconductivity. Here, we report a comprehensive suite of high magnetic field measurements on a generation of pristine quality UTe2 crystals. Our experiments reveal a significantly revised high magnetic field superconducting phase diagram in the ultraclean limit, showing a pronounced sensitivity of field-induced superconductivity to the presence of crystalline disorder. We employ a Ginzburg-Landau model that excellently captures this acute dependence on sample quality. Our results suggest that in close proximity to a field-induced metamagnetic transition the enhanced role of magnetic fluctuations--that are strongly suppressed by disorder--is likely responsible for tuning UTe2 between two distinct spin-triplet superconducting phases. [ABSTRACT FROM AUTHOR]

UCoGe is an archetype of coexisting weak itinerant 5f-electron ferromagnetism (TC ~ 3 K,μs = 0:03μB/f.u.) and superconductivity (TSC ~ 0:6 K) at ambient pressure. The Ru substitution for Co leads to an initial sharp increase of the TC up to the maximum of TC = 8:5 K for x = 0:12, increase of spontaneous magnetic moment and suppression of superconductivity. We have grown the UCo0:88Ru0:12Ge single crystal and studied magnetization along the principal crystallographic axes. To see the microscopic background of these findings we performed a polarized neutron diffraction experiment on D3 diffractometer in ILL. We have found that the Co and U moments are parallel in UCo0:88Ru0:12Ge, in contrast to the antiparallel configuration in UCoGe. This is probably the reason of the spontaneous magnetization increase with Ru doping. [ABSTRACT FROM AUTHOR]

Magnetotransport constitutes a useful probe to understand the interplay between electronic band topology and magnetism in spintronic devices. A recent theory of Lu and Shen [Phys. Rev. Lett. 112, 146601 (2014)] on magnetically doped topological insulators predicts that quantum corrections Δκ to the temperature dependence of conductivity can change sign across the Curie transition. This phenomenon has been attributed to a suppression of the Berry phase of the topological surface states at the Fermi level, caused by a magnetic energy gap. Here, we demonstrate experimentally that Δκ can reverse its sign even when the Berry phase at the Fermi level remains unchanged. The contradictory behavior to theory predictions is resolved by extending the model by Lu and Shen to a nonmonotonic temperature scaling of the inelastic scattering length showing a turning point at the Curie transition. [ABSTRACT FROM AUTHOR]

Below a critical temperature [Formula: see text], superconductors transport electrical charge without dissipative energy losses. The application of a magnetic field [Formula: see text] generally acts to suppress [Formula: see text], up to some critical field strength at which [Formula: see text] 0 K. Here, we investigate magnetic field-induced superconductivity in high-quality specimens of the triplet superconductor candidate UTe[Formula: see text] in pulsed magnetic fields up to [Formula: see text] [Formula: see text] 70 T. Strikingly, we find that this material has a higher [Formula: see text] when [Formula: see text] 40 T ([Formula: see text] 2.4 K) than it does for [Formula: see text] 0 T ([Formula: see text] 2.1 K). This observation points to a fundamentally distinct mechanism for the formation of superconductivity at high [Formula: see text] in UTe[Formula: see text] compared to the case of [Formula: see text] [Formula: see text] 0 T., Competing Interests: Competing interests statement:The authors declare no competing interest.

The study of magnetic frustration in classical spin systems is motivated by the prediction and discovery of classical spin liquid states. These uncommon magnetic phases are characterized by a massive degeneracy of their ground state implying a finite magnetic entropy at zero temperature. While the classical spin liquid state is originally predicted in the Ising triangular lattice antiferromagnet in 1950, this state has never been experimentally observed in any triangular magnets. The discovery of an electric analogue of classical spin liquids on a triangular lattice of uniaxial electric dipoles in EuAl 12 O 19 is reported here. This new type of frustrated antipolar phase is characterized by a highly-degenerate state at low temperature implying an absence of long-range antiferroelectric order, despite short-range antipolar correlations. Its dynamics are governed by a thermally activated process, slowing down upon cooling toward a complete freezing at zero temperature., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

The unconventional superconductor UTe[Formula: see text] exhibits numerous signatures of spin-triplet superconductivity-a rare state of matter which could enable quantum computation protected against decoherence. UTe[Formula: see text] possesses a complex phase landscape comprising two magnetic field-induced superconducting phases, a metamagnetic transition to a field-polarized state, along with pair- and charge-density wave orders. However, contradictory reports between studies performed on UTe[Formula: see text] specimens of varying quality have severely impeded theoretical efforts to understand the microscopic origins of the exotic superconductivity. Here, we report a comprehensive suite of high magnetic field measurements on a generation of pristine quality UTe[Formula: see text] crystals. Our experiments reveal a significantly revised high magnetic field superconducting phase diagram in the ultraclean limit, showing a pronounced sensitivity of field-induced superconductivity to the presence of crystalline disorder. We employ a Ginzburg-Landau model that excellently captures this acute dependence on sample quality. Our results suggest that in close proximity to a field-induced metamagnetic transition the enhanced role of magnetic fluctuations-that are strongly suppressed by disorder-is likely responsible for tuning UTe[Formula: see text] between two distinct spin-triplet superconducting phases., Competing Interests: Competing interests statement:The authors declare no competing interest.

UTe_{2} is a spin-triplet superconductor candidate for which high quality samples with long mean free paths have recently become available, enabling quantum oscillation measurements to probe its Fermi surface and effective carrier masses. It has recently been reported that UTe_{2} possesses a 3D Fermi surface component [Phys. Rev. Lett. 131, 036501 (2023)PRLTAO0031-900710.1103/PhysRevLett.131.036501]. The distinction between 2D and 3D Fermi surface sections in triplet superconductors can have important implications regarding the topological properties of the superconductivity. Here we report the observation of oscillatory components in the magnetoconductance of UTe_{2} at high magnetic fields. We find that these oscillations are well described by quantum interference between quasiparticles traversing semiclassical trajectories spanning magnetic breakdown networks. Our observations are consistent with a quasi-2D model of this material's Fermi surface based on prior dHvA-effect measurements. Our results strongly indicate that UTe_{2}-which exhibits a multitude of complex physical phenomena-possesses a remarkably simple Fermi surface consisting exclusively of two quasi-2D cylindrical sections.

We present acoustic signatures of the electric quadrupolar degrees of freedom in the honeycomb-layer compound UNi_{4}B. The transverse ultrasonic mode C_{66} shows softening below 30 K both in the paramagnetic phase and antiferromagnetic phases down to ∼0.33  K. Furthermore, we traced magnetic field-temperature phase diagrams up to 30 T and observed a highly anisotropic elastic response within the honeycomb layer. These observations strongly suggest that Γ_{6}(E_{2g}) electric quadrupolar degrees of freedom in localized 5f^{2} (J=4) states are playing an important role in the magnetic toroidal dipole order and magnetic-field-induced phases of UNi_{4}B, and evidence some of the U ions remain in the paramagnetic state even if the system undergoes magnetic toroidal ordering.

There is an ongoing dispute in the community about the absence of a magnetic quantum critical point (QCP) in the noncentrosymmetric heavy fermion compound CeRhSi 3 . In order to explore this question we prepared single crystals of CeRh(Si 1- x Ge x ) 3 with x = 0.05 and 0.15 and determined the temperature-pressure ( T - p ) phase diagram by means of measurements of the electrical resistivity. The substitution of isoelectronic but large Ge enforces a lattice volume increase resulting in a weakening of the Kondo interaction. As a result, the x = 0.05 and x = 0.15 compound exhibit a transition into the antiferromagnetic (AFM) at higher temperatures being T N = 4.7 K and T N1 = 19.7 K, respectively. Application of pressure suppresses T N ( T N1 ) monotonically and pressure induced superconductivity is observed in both Ge-substituted compounds above p ⩾ 2.16 GPa ( x = 0.05) and p ⩾ 2.93 GPa ( x = 0.15). Extrapolation of T N ( p ) → 0 of CeRh(Si 0.95 Ge 0.05 ) 3 yields a critical pressure of p c ≈ 3.4 GPa (in CeRh(Si 0.85 Ge 0.15 ) 3   p c ≈ 3.5 GPa) pointing to the presence of an AFM QCP located deep inside the superconducting state., (© 2020 IOP Publishing Ltd.)