Study of magnetoelastic interaction in MnF2_2 by the acoustoelectric transformation method

The mechanisms of magnetoelastic interaction in MnF$_2$ are studied using the method of acoustoelectric transformation. The temperature dependence of the piezomagnetic coupling coefficient and its anisotropy are determined in the antiferromagnetic phase. We observe a new effect consisting in the appearance of a non-diagonal component of the magnetic susceptibility tensor, which is proportional to the square of the order parameter, under the action of the shear wave. A phenomenological interpretation of the effect, which takes into account a small-angle rotation of the crystal lattice, is presented. In the paramagnetic state, the effect of acoustic deformation is reduced to the modulation of the diagonal component of the susceptibility tensor

Enhanced triplet superconductivity in next generation ultraclean UTe2

The spin-triplet superconductor UTe$_2$ exhibits a myriad of exotic physical phenomena, including the possession of three distinct superconducting phases at ambient pressure for magnetic field $\mu_0 H \leq$ 40 T aligned in certain orientations. However, contradictory reports between studies performed on UTe$_2$ specimens of varying quality have severely impeded theoretical efforts to understand the microscopic properties of this material. Here, we report high magnetic field measurements on a new generation of ultraclean UTe$_2$ specimens, which possess enhanced superconducting critical temperatures and fields compared to previous sample generations. Remarkably, for $H$ applied close to the hard magnetic $b$ direction, we find that the angular extent of magnetic field-reinforced superconductivity is significantly increased in these high purity crystals. This suggests that, in 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$_2$ between two distinct spin-triplet superconducting phases. Our results reveal a strong sensitivity to crystalline disorder of the field-reinforced superconducting state of UTe$_2$

Research data supporting: "Quantum interference between quasi-2D Fermi surface sheets in UTe2" Weinberger, T.I. et al.

Supporting research data of quantum interference oscillations. Data were measured in the 41 T all-resistive magnet in NHMFL, Tallahassee, by the TDO technique, and in a 70 T coil in HLD, Dresden, by the PDO technique

Quantum Interference between Quasi-2D Fermi Surface Sheets in UTe2

UTe2 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 UTe2 possesses a 3D Fermi surface component [Phys. Rev. Lett. 131, 036501 (2023)]. 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 UTe2 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 UTe2—which exhibits a multitude of complex physical phenomena—possesses a remarkably simple Fermi surface consisting exclusively of two quasi-2D cylindrical section

Research data supporting "Quasi-2D Fermi surface in the anomalous superconductor UTe2"

Research data supporting "Quasi-2D Fermi surface in the anomalous superconductor UTe2" Quantum oscillation data were obtained by the capacitive cantilever beam magnetometry method. Data were recorded at the National High Magnetic Field Lab, Tallahassee, Florida, USA. Measurements were performed in SCM4, an all-superconducting magnet, which enabled a sample environment of 19-200 mK with applied fields of 0-28 T

Quasi-2D Fermi surface in the anomalous superconductor UTe2

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

Research data supporting: Enhanced triplet superconductivity in next generation ultraclean UTe₂

Research data supporting "Enhanced triplet superconductivity in next generation ultraclean UTe₂" High magnetic field data were obtained at NHMFL Florida and HLD Dresden, by contacted and contactless conductivity techniques. Low field data were obtained in the Department of Physics, University of Cambridge, including the Advanced Materials Characterisation Suite, Maxwell Centre, University of Cambridge

Quasi-2D Fermi surface in the anomalous superconductor UTe2

Funder: MEXT | Japan Atomic Energy Agency (JAEA); doi: https://doi.org/501100005118Funder: Czech Science Foundation (GACR) 22-22322S; Czech Research Infrastructures LM2018096AbstractThe 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.</jats:p

Enhanced triplet superconductivity in next-generation ultraclean UTe2.

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