2,463 research outputs found
Anomalous Anisotropic Magnetoresistance in Heavy-Fermion PrFe4P12
We have investigated the anisotropy of the magnetoresistance in the Pr-based
HF compound PrFe4P12. The large anisotropy of effective mass and its strong
field dependence have been confirmed by resistivity measurements. Particularly
for H||[111], where the effective mass is most strongly enhanced, the non-Fermi
liquid behavior has been observed. Also, we have found the angular dependence
of the magnetoresistance sharply enhanced at H||[111], which is evidently
correlated with both the non-Fermi liquid behavior and the high-field ordered
state (B-phase).Comment: 3 pages, 3 figures. J. Phys. Soc. Jpn. Vol.77, No.8, in pres
Evolution of superconducting order in Pr(OsRu)Sb
We report measurements of the magnetic penetration depth in single
crystals of Pr(OsRu)Sb down to 0.1 K. Both
and superfluid density exhibit an exponential behavior for the
0.4 samples, going from weak (=0.4,0.6), to moderate, coupling
(=0.8). For the 0.2 samples, both and vary as
at low temperatures, but is s-wave-like at intermediate to
high temperatures. Our data are consistent with a three-phase scenario, where a
fully-gapped phase at undergoes two transitions: first to an
unconventional phase at , then to a nodal low-
phase at , for small values of .Comment: Changed title, enlarged numbering in figures 5 pages, 4 figures, 1
tabl
Anomalous Metal-Insulator Transition in Filled Skutterudite CeOsSb
Anomalous metal-insulator transition observed in filled skutterudite
CeOsSb is investigated by constructing the effective tight-binding
model with the Coulomb repulsion between f electrons. By using the mean field
approximation, magnetic susceptibilities are calculated and the phase diagram
is obtained. When the band structure has a semimetallic character with small
electron and hole pockets at and H points, a spin density wave
transition with the ordering vector occurs due to the
nesting property of the Fermi surfaces. Magnetic field enhances this phase in
accord with the experiments.Comment: 4 pages, 4 figure
High magnetic field phase diagram of PrOs4Sb12
The magnetic phase diagram of PrOsSb has been investigated by
specific heat measurements between 8 and 32 T. A new Schottky anomaly due to
excitations between two lowest crystalline-electric-field (CEF) singlets, has
been found for both and above the field
where the field-induced ordered phase (FIOP) is suppressed. The constructed
phase diagram shows weak magnetic anisotropy and implies a crossing of
the two CEF levels at about 8 - 9 T for both field directions. These results
provide an unambiguous evidence for the singlet being the CEF ground
state and suggest the level crossing (involving lowest CEF levels) as the
driving mechanism of FIOP.Comment: Submitted to Phys. Rev. Let
Thermodynamics of Superstring on Near-extremal NS5 and Effective Hagedorn Behavior
We study the thermodynamical torus partition function of superstring on the
near-extremal black NS5-brane background. The exact partition function has been
computed with the helps of our previous works:[arXiv:1012.5721 [hep-th]],
[arXiv:1109.3365 [hep-th]], and naturally decomposed into two parts. The first
part is contributed from strings freely propagating in the asymptotic region,
which are identified as the superstring gas at the Hawking temperature on the
linear-dilaton background. The second part includes the contribution localized
around the `tip of cigar', which characterizes the non-extremality. Remarkably,
the latter part includes massless excitations with non-vanishing thermal
winding, which signifies that the Hagedorn-like behavior effectively appears,
even though the Hawking temperature is much lower than the Hagedorn
temperature. We also explore the high-temperature backgrounds defined by the
orbifolding along the Euclidean time direction. In those cases, the thermal
winding modes localized around the tip are found to be tachyonic, reflecting
the singularities of Euclidean backgrounds caused by orbifolding.Comment: 1+29 pages, no figure; v2 the footnote 1 is enhanced, to appear in
JHE
Penetration depth study of LaOsSb: Multiband s-wave superconductivity
We measured the magnetic penetration depth in single crystals of
LaOsSb (=0.74 K) down to 85 mK using a tunnel diode
oscillator technique. The observed low-temperature exponential dependence
indicates a s-wave gap. Fitting the low temperature data to BCS s-wave
expression gives the zero temperature gap value which is significantly smaller than the BCS value of 1.76. In
addition, the normalized superfluid density shows an unusually long
suppression near , and are best fit by a two-band s-wave model.Comment: 5 pages, 2 figure
High-Field de Haas-van Alphen Effect in non-centrosymmetric CeCoGe3 and LaCoGe3
We report on de Haas-van Alphen effect measurements in the
non-centrosymmetric systems CeCoGe3 and LaCoGe3 in magnetic field up to 28
Tesla. In both compounds, two new high frequencies were observed in high
fields. The frequencies were not detected in previous lower field measurements.
The frequencies do not originate from magnetic breakdown, and, therefore, are
likely to be intrinsic features of the compounds. In CeCoGe3, the corresponding
effective masses are strongly enhanced, being of the order of 30 bare electron
masses.Comment: 3 pages, 4 figures, to be published in Proc. Int. Conf. Heavy
Electrons (ICHE2010) J. Phys. Soc. Jpn. 80 (2011
- …