115 research outputs found
Angular variation of the magnetoresistance of the superconducting ferromagnet UCoGe
We report a magnetoresistance study of the superconducting ferromagnet UCoGe.
The data, taken on single-crystalline samples, show a pronounced structure at
~T for a field applied along the ordered moment . Angle
dependent measurements reveal this field-induced phenomenon has an uniaxial
anisotropy. Magnetoresistance measurements under pressure show a rapid increase
of to 12.8~T at 1.0~GPa. We discuss in terms of a field induced
polarization change. Upper critical field measurements corroborate the unusual
S-shaped -curve for a field along the -axis of the orthorhombic
unit cell.Comment: 6 pages, 5 figures; accepted for publication in Phys. Rev.
Balanced electron-hole transport in spin-orbit semimetal SrIrO3 heterostructures
Relating the band structure of correlated semimetals to their transport
properties is a complex and often open issue. The partial occupation of
numerous electron and hole bands can result in properties that are seemingly in
contrast with one another, complicating the extraction of the transport
coefficients of different bands. The 5d oxide SrIrO3 hosts parabolic bands of
heavy holes and light electrons in gapped Dirac cones due to the interplay
between electron-electron interactions and spin-orbit coupling. We present a
multifold approach relying on different experimental techniques and theoretical
calculations to disentangle its complex electronic properties. By combining
magnetotransport and thermoelectric measurements in a field-effect geometry
with first-principles calculations, we quantitatively determine the transport
coefficients of different conduction channels. Despite their different
dispersion relationships, electrons and holes are found to have strikingly
similar transport coefficients, yielding a holelike response under field-effect
and thermoelectric measurements and a linear, electronlike Hall effect up to 33
T.Comment: 5 pages, 4 figure
Characterization of fast magnetosonic waves driven by interaction between magnetic fields and compact toroids
Magnetosonic waves are low-frequency, linearly polarized magnetohydrodynamic
(MHD) waves that can be excited in any electrically conducting fluid permeated
by a magnetic field. They are commonly found in space, responsible for many
well-known features, such as heating of the solar corona and acceleration of
energetic electrons in Earth's inner magnetosphere. In this work, we present
observations of magnetosonic waves driven by injecting compact toroid (CT)
plasmas into a static Helmholtz magnetic field at the Big Red Ball (BRB)
Facility at Wisconsin Plasma Physics Laboratory (WiPPL). We first identify the
wave modes by comparing the experimental results with the MHD theory, and then
study how factors such as the background magnetic field affect the wave
properties. Since this experiment is part of an ongoing effort of forming a
target plasma with tangled magnetic fields as a novel fusion fuel for
magneto-inertial fusion (MIF, aka magnetized target fusion), we also discuss a
future possible path of forming the target plasma based on our current results
Emergence of the nematic electronic state in FeSe
We present a comprehensive study of the evolution of the nematic electronic
structure of FeSe using high resolution angle-resolved photoemission
spectroscopy (ARPES), quantum oscillations in the normal state and
elastoresistance measurements. Our high resolution ARPES allows us to track the
Fermi surface deformation from four-fold to two-fold symmetry across the
structural transition at ~87 K which is stabilized as a result of the dramatic
splitting of bands associated with dxz and dyz character. The low temperature
Fermi surface is that a compensated metal consisting of one hole and two
electron bands and is fully determined by combining the knowledge from ARPES
and quantum oscillations. A manifestation of the nematic state is the
significant increase in the nematic susceptibility as approaching the
structural transition that we detect from our elastoresistance measurements on
FeSe. The dramatic changes in electronic structure cannot be explained by the
small lattice effects and, in the absence of magnetic fluctuations above the
structural transition, points clearly towards an electronically driven
transition in FeSe stabilized by orbital-charge ordering.Comment: Latex, 8 pages, 4 figure
Evolution of the Fermi surface of BaFe_2(As_{1-x}P_x)_2 on entering the superconducting dome
Using the de Haas-van Alphen effect we have measured the evolution of the
Fermi surface of BaFe_2(As_{1-x}P_x)_2 as function of isoelectric substitution
(As/P) for 0.41<x<1 (T_c up to 25 K). We find that the volume of electron and
hole Fermi surfaces shrink linearly with decreasing x. This shrinking is
accompanied by a strong increase in the quasiparticle effective mass as x is
tuned toward the maximum T_c. It is likely that these trends originate from the
many-body interaction which give rise to superconductivity, rather than the
underlying one-electron bandstructure.Comment: 4 page
- …