41 research outputs found
Magnetoelastics of High Field Phenomena in Antiferromagnets UO2 and CeRhIn5
We use a recently developed optical fiber Bragg grating technique, in
continuous and pulsed magnetic fields in excess of 90T, to study magnetoelastic
correlations in magnetic materials at cryogenic temperatures. Both insulating
UO2 and metallic CeRhIn5 present antiferromagnetic ground states, at T_N =
30.3K and T_N = 3.85K respectively. A strong coupling of the magnetism to the
crystal lattice degrees of freedom in UO2 is found, revealing piezomagnetism as
well as the dynamics of antiferromagnetic domain switching between spin
arrangements connected by time reversal. The AFM domains become harder to
switch as the temperature is reduced, reaching a record value H_PZ(T = 4K) =
18T. The effect of strong magnetic fields is also studied in CeRhIn5, where an
anomaly in the sample crystallographic c-axis of magnitude Delta_c/c = 2 ppm is
found associated to a recently proposed electronic nematic state at H_en = 30T
applied 11o off the c-axis. Here we show that while this anomaly is absent when
the magnetic field is applied 18o off the a-axis, strong magnetoelastic quantum
oscillations attest to the high quality of the single crystal samples.Comment: 5 pages, figures include
Boundary scattering in micro-size crystal of topological Kondo insulator SmB
We have studied the effects of phonon-boundary scattering on the thermal
transport in topological Kondo insulator, SmB. The studies have been
performed by using the method in the temperature range 300K - 3K. We
show that the observed thermal conductivity of micro-size SmB is of the
order of magnitude smaller than for a bulk single-crystal. Using the Callaway
model we analyzed the low-temperature lattice thermal conductivity of the micro
crystal and show that phonon scattering by sample boundaries plays a major role
in the thermal resistance in this topological material. In addition, we show
that the temperature dependence of the lattice thermal conductivity shows a
double peak structure that suggests complex phonon-phonon or phonon-defects
interactions in SmB. These findings provide guidance for the understanding
of the thermal transport of advanced materials and devices at a micro-scale.Comment: 5 pages including references, 3 figure
Phonon thermal transport in UO via self-consistent perturbation theory
Computing thermal transport from first-principles in UO is complicated
due to the challenges associated with Mott physics. Here we use irreducible
derivative approaches to compute the cubic and quartic phonon interactions in
UO from first-principles, and we perform enhanced thermal transport
computations by evaluating the phonon Green's function via self-consistent
diagrammatic perturbation theory. Our predicted phonon lifetimes at K
agree well with our inelastic neutron scattering measurements across the entire
Brillouin zone, and our thermal conductivity predictions agree well with
previous measurements. Both the changes due to thermal expansion and
self-consistent contributions are nontrivial at high temperatures, though the
effects tend to cancel, and interband transitions yield a substantial
contribution
Unusual magnetic and transport properties in HoMnSn kagome magnet
With intricate lattice structures, kagome materials are an excellent platform
to study various fascinating topological quantum states. In particular, kagome
materials, revealing large responses to external stimuli such as pressure or
magnetic field, are subject to special investigation. Here, we study the
kagome-net HoMnSn magnet that undergoes paramagnetic to ferrimagnetic
transition (below 376 K) and reveals spin-reorientation transition below 200 K.
In this compound, we observe the topological Hall effect and substantial
contribution of anomalous Hall effect above 100 K. We unveil the pressure
effects on magnetic ordering at a low magnetic field from the pressure tunable
magnetization measurement. By utilizing high-resolution angle-resolved
photoemission spectroscopy, Dirac-like dispersion at the high-symmetry point K
is revealed in the vicinity of the Fermi level, which is well supported by the
first-principles calculations, suggesting a possible Chern-gapped Dirac cone in
this compound. Our investigation will pave the way to understand the
magneto-transport and electronic properties of various rare-earth-based kagome
magnets