584 research outputs found
Crossed Andreev reflection as a probe for the pairing symmetry of Ferromagnetic Superconductors
The coexistence of superconductivity and ferromagnetism has brought about the
phenomena of ferromagnetic superconductors. The theory needed to understand the
compatibility of such antagonistic phenomena cannot be built until the pairing
symmetry of such superconductors is correctly identified. The proper and
unambiguous identification of the pairing symmetry of such superconductors is
the subject of this paper. This work shows that crossed Andreev reflection can
be a very effective tool in order to identify the pairing symmetry of these
superconductors.Comment: 5 pages, 1 figure, 1 table. Accepted for publication in Phys. Rev.
B(Rapid Communication
Fermi Surface Instabilities in Ferromagnetic Superconductor URhGe
The field-reentrant (field-reinforced) superconductivity on ferromagnetic
superconductors is one of the most interesting topics in unconventional
superconductivity. The enhancement of effective mass and the induced
ferromagnetic fluctuations play key roles for reentrant superconductivity.
However, the associated change of the Fermi surface, which is often observed at
(pseudo-) metamagnetic transition, can also be a key ingredient. In order to
study the Fermi surface instability, we performed Hall effect measurements in
the ferromagnetic superconductor URhGe. The Hall effect of URhGe is well
explained by two contributions, namely by the normal Hall effect and by the
large anomalous Hall effect due to skew scattering. The large change in the
Hall coefficient is observed at low fields between the paramagnetic and
ferromagnetic states for H // c-axis (easy-magnetization axis) in the
orthorhombic structure, indicating that the Fermi surface is reconstructed in
the ferromagnetic state below the Curie temperature (T_Curie=9.5K). At low
temperatures (T << T_Curie), when the field is applied along the b-axis, the
reentrant superconductivity was observed in both the Hall resistivity and the
magnetoresistance below 0.4K. Above 0.4K, a large jump with the first-order
nature was detected in the Hall resistivity at a spin-reorientation field H_R ~
12.5T, demonstrating that the marked change of the Fermi surface occurs between
the ferromagnetic state and the polarized state above H_R. The results can be
understood by the Lifshitz-type transition, induced by the magnetic field or by
the change of the effective magnetic field.Comment: 7 pages, 6 figures, accepted for publication in J. Phys. Soc. Jp
Similarity of Fermi Surface in the Hidden Order State and in the Antiferromagnetic State of URu2Si2
Shubnikov-de Haas measurements of high quality URu2Si2 single crystals reveal
two previously unobserved Fermi surface branches in the so-called hidden order
phase. Therefore about 55% of the enhanced mass is now detected. Under pressure
in the antiferromagnetic state, the Shubnikov-de Haas frequencies for magnetic
fields applied along the crystalline c axis show little change compared with
the zero pressure data. This implies a similar Fermi surface in both the hidden
order and antiferromagnetic states, which strongly suggests that the lattice
doubling in the antiferromagnetic phase due to the ordering vector QAF = (0 0
1) already occurs in the hidden order. These measurements provide a good test
for existing or future theories of the hidden order parameter.Comment: 4 pages, 4 figure
On the destruction of the hidden order in URuSi by a strong magnetic field
We present a study of transport properties of the heavy fermion URuSi
in pulsed magnetic field. The large Nernst response of the hidden order state
is found to be suppressed when the magnetic field exceeds 35 T. The combination
of resistivity, Hall and Nernst data outlines the reconstruction of the Fermi
surface in the temperature-field phase diagram. The zero-field ground state is
a compensated heavy-electron semi-metal, which is destroyed by magnetic field
through a cascade of field-induced transitions. Above 40 T, URuSi
appears to be a polarized heavy fermions metal with a large density of carriers
whose effective mass rapidly decreases with increasing magnetic polarization.Comment: published versio
Thermoelectric response near a quantum critical point of beta-YbAlB4 and YbRh2Si2: A comparative study
The thermoelectric coefficients have been measured on the Yb-based heavy
fermion compounds beta-YbAlB4 and YbRh2Si2 down to a very low temperature. We
observe a striking difference in the behavior of the Seebeck coefficient, S in
the vicinity of the Quantum Critical Point (QCP) in the two systems. As the
critical field is approached, S/T enhances in beta-YbAlB4 but is drastically
reduced in YbRh2Si2. While in the former system, the ratio of
thermopower-to-specific heat remains constant, it drastically drops near the
QCP in YbRh2Si2. In both systems, on the other hand, the Nernst coefficient
shows a diverging behavior near the QCP. The results provide a new window to
the way various energy scales of the system behave and eventually vanish near a
QCP
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