118 research outputs found
Intrinsically Legal-For-Trade Objects by Digital Signatures
The established techniques for legal-for-trade registration of weight values
meet the legal requirements, but in praxis they show serious disadvantages. We
report on the first implementation of intrinsically legal-for-trade objects,
namely weight values signed by the scale, that is accepted by the approval
authority. The strict requirements from both the approval- and the
verification-authority as well as the limitations due to the hardware of the
scale were a special challenge. The presented solution fulfills all legal
requirements and eliminates the existing practical disadvantages.Comment: 4 pages, 0 figure
Andreev reflection at point contacts with heavy-fermion UBe13 ?
We comment on a recent Letter by Waelti et al. (PRL 84, 5616 (2000)) on
'Spectroscopic evidence for unconventional superconductivity in UBe13'. We show
- by using the basic Wexler formula - that it is unlikely to observe Andreev
reflection at point contacts between UBe13 and a normal metal. The large
superconducting anomalies usually found for those contacts are mainly due to
the resistive Maxwell resistance vanishing below Tc of UBe13.Comment: 1 page, no figures, RevTeX, submitted to Phys. Rev. Let
Competition between phonon superconductivity and Kondo screening in mixed valence and heavy fermion compounds
We consider competition of Kondo effect and s-wave superconductivity in heavy
fermion and mixed valence superconductors, using the phenomenological approach
for the periodic Anderson model. Similar to the well known results for
single-impurity Kondo effect in superconductors, we have found principal
possibility of a re-entrant regime of the superconducting transition
temperature, , in heavy fermion superconductors in a narrow range of model
parameters and concentration of f-electrons. Suppression of in mixed
valence superconductors is much weaker. Our theory has most validity in the
low-temperature Fermi liquid regime, without re-entrant behavior of . To
check its applicability, we performed the fit for the -dependence of
in CeLaRuSi and obtained an excellent agreement with the
experimental data, although no re-entrance was found in this case. Other
experimental data are discussed in the light of our theoretical analysis. In
particular, we compare temperatures of the superconducting transition for some
known homologs, i.e., the analog periodic lattice compounds with and without
f-elements. For a few pairs of homologs superconductivity exists only in the
heavy fermion materials, thus confirming uniqueness of superconductivity
mechanisms for the latter. We suggest that for some other compounds the value
of may remain of the same order in the two homologs, if superconductivity
originates mainly on some light Fermi surface, but induces sizable
superconducting gap on another Fermi surface,for which hybridization or other
heavy fermion effects are more significant.Comment: 11 pages, 4 figures, pd
Heavy fermion superconductivity and magnetic order in non-centrosymmetric
is a novel heavy fermion superconductor, crystallising in the
structure as a tetragonally distorted low symmetry variant of the
structure type. exhibits antiferromagnetic order at
K and enters into a heavy fermion superconducting state at
K. Large values of T/K and T refer to heavy quasiparticles forming Cooper pairs. Hitherto, is the first heavy fermion superconductor without a center of
symmetry.Comment: 4 pages, 4 figure
Critical Fields of the "Heavy-Fermion" Superconductor CeCu2Si2
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Effects of La substitution on superconducting state of CeCoIn5
We report effects of La substitution on superconducting state of heavy
fermion superconductor CeCoIn5, as seen in transport and magnetization
measurements. As opposed to the case of conventional superconductors, pair
breaking by nonmagnetic La results in depression of Tc and indicates strong gap
anisotropy. Upper critical field Hc2 values decrease with increased La
concentration, but the critical field anisotropy, gamma=Hc2(a)/Hc2(c), does not
change in the Ce_{1-x}La_xCoIn5 (x=0-0.15). The electronic system is in the
clean limit for all values of x.Comment: Submitted to Phys. Rev.
Superconductivity in the Ferroquadrupolar State in the Quadrupolar Kondo Lattice PrTiAl
The cubic compound PrTiAl is a quadrupolar Kondo lattice system
that exhibits quadrupolar ordering due to the non-Kramers ground
doublet and has strong hybridization between and conduction electrons. Our
study using high-purity single crystal reveals that PrTiAl exhibits
type-II superconductivity at mK in the nonmagnetic
ferroquadrupolar state. The superconducting critical temperature and field
phase diagram suggests moderately enhanced effective mass of
Superconductivity on the threshold of magnetism in CePd2Si2 and CeIn3
The magnetic ordering temperature of some rare earth based heavy fermion
compounds is strongly pressure-dependent and can be completely suppressed at a
critical pressure, p, making way for novel correlated electron states close
to this quantum critical point. We have studied the clean heavy fermion
antiferromagnets CePdSi and CeIn in a series of resistivity
measurements at high pressures up to 3.2 GPa and down to temperatures in the mK
region. In both materials, superconductivity appears in a small window of a few
tenths of a GPa on either side of p. We present detailed measurements of
the superconducting and magnetic temperature-pressure phase diagram, which
indicate that superconductivity in these materials is enhanced, rather than
suppressed, by the closeness to magnetic order.Comment: 11 pages, including 9 figure
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