77 research outputs found
Magnetic Properties of YbBe13 Probed by Neutron Scattering and Thermodynamic Measurements
We examined the magnetic properties of YbBe13, which exhibits an
antiferromagnetic order below TN = 1.2 K. Unlike other MBe13 compounds (M =
rare earth/actinide elements), based on elastic neutron scattering, we observed
an incommensurate magnetic propagation vector {\tau} = (0,0,{\tau}z), where
{\tau}z = 0.5385 is in the reciprocal lattice unit. Additionally, we
constructed a precise magnetic phase diagram for YbBe13. We observed
non-trivial magnetic anomalies in YbBe13, which cannot be understood based on a
simple helical order. Our results for YbBe13 provide an opportunity to
reconsider the electron state of UBe13 and present an important step toward a
comprehensive understanding of magnetic correlations in MBe13 series.Comment: 5 pages, 5 figure
Pressure-induced structural phase transition and new superconducting phase in UTe2
We report on the crystal structure and electronic properties of the heavy
fermion superconductor UTe2 at high pressure up to 11 GPa, as investigated by
X-ray diffraction and electrical resistivity experiments. The X-ray diffraction
measurements under high pressure using a synchrotron light source reveal
anisotropic linear compressibility of the unit cell up to 3.5 GPa, while a
pressure-induced structural phase transition is observed above 3.5-4GPa at room
temperature, where the body-centered orthorhombic crystal structure with the
space group Immm changes into a body-centered tetragonal structure with the
space group I4/mmm. The molar volume drops abruptly at the critical pressure,
while the distance between the first-nearest neighbor of U atoms increases,
implying a switch from the heavy electronic states to the weakly correlated
electronic states. Surprisingly, a new superconducting phase at pressures
higher than 7 GPa was detected at Tsc above 2K with a relatively low
upper-critical field, Hc2(0). The resistivity above 3.5GPa, thus, in the
high-pressure tetragonal phase, shows a large drop below 230 K, which may also
be related to a considerable change from the heavy electronic states to the
weakly correlated electronic states.Comment: 11 pages, 9 figure
Orientation of point nodes and nonunitary triplet pairing tuned by the easy-axis magnetization in UTe2
The gap structure of a novel uranium-based superconductor UTe, situated
in the vicinity of ferromagnetic quantum criticality, has been investigated via
specific-heat measurements in various field orientations. Its
angular variation shows a characteristic shoulder anomaly
with a local minimum in at moderate fields rotated within the
and planes. Based on the theoretical calculations, these features can
be attributed to the presence of point nodes in the superconducting gap along
the direction. Under the field orientation along the easy-magnetization
axis, an unusual temperature dependence of the upper critical field at low
fields together with a convex downward curvature in were observed. These
anomalous behaviors can be explained on the basis of a nonunitary triplet state
model with equal-spin pairing whose is tuned by the magnetization
along the axis. From these results, the gap symmetry of UTe is most
likely described by a vector order parameter of .Comment: 6 pages, 4 figures (main text) + 7 pages, 5 figures (Supplementary
Material), accepted for publication in Phys. Rev. Researc
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