22,216 research outputs found
Transport properties and anisotropy in rare earth doped CaFe2As2 single crystals with Tc above 40 K
In this paper we report the superconductivity above 40 K in the electron
doping single crystal Ca1-xRexFe2As2 (Re = La, Ce, Pr). The x-ray diffraction
patterns indicate high crystalline quality and c-axis orientation. the
resistivity anomaly in the parent compound CaFe2As2 is completely suppressed by
partial replacement of Ca by rare earth and a superconducting transition
reaches as high as 43 K, which is higher than the value in electron doping
FeAs-122 compounds by substituting Fe ions with transition metal, even
surpasses the highest values observed in hole doping systems with a transition
temperature up to 38 K. The upper critical field has been determined with the
magnetic field along ab-plane and c-axis, yielding the anisotropy of 2~3.
Hall-effect measurements indicate that the conduction in this material is
dominated by electron like charge carriers. Our results explicitly demonstrate
the feasibility of inducing superconductivity in Ca122 compounds via electron
doping using aliovalent rare earth substitution into the alkaline earth site,
which should add more ingredients to the underlying physics of the iron-based
superconductors.Comment: 21 pages, 7 figure
Observation of Landau quantization and standing waves in HfSiS
Recently, HfSiS was found to be a new type of Dirac semimetal with a line of
Dirac nodes in the band structure. Meanwhile, Rashba-split surface states are
also pronounced in this compound. Here we report a systematic study of HfSiS by
scanning tunneling microscopy/spectroscopy at low temperature and high magnetic
field. The Rashba-split surface states are characterized by measuring Landau
quantization and standing waves, which reveal a quasi-linear dispersive band
structure. First-principles calculations based on density-functional theory are
conducted and compared with the experimental results. Based on these
investigations, the properties of the Rashba-split surface states and their
interplay with defects and collective modes are discussed.Comment: 6 pages, 5 figure
A New Solution of the Yang-Baxter Equation Related to the Adjoint Representation of
A new solution of the Yang-Baxter equation, that is related to the adjoint
representation of the quantum enveloping algebra , is obtained by
fusion formulas from a non-standard solution.Comment: 16 pages (Latex), Preprint BIHEP-TH-93-3
Chiral bands for quasi-proton and quasi-neutron coupling with a triaxial rotor
A particle rotor model (PRM) with a quasi-proton and a quasi-neutron coupled
with a triaxial rotor is developed and applied to study chiral doublet bands
with configurations of a proton and a quasi-neutron. With
pairing treated by the BCS approximation, the present quasi-particle PRM is
aimed at simulating one proton and many neutron holes coupled with a triaxial
rotor. After a detailed analysis of the angular momentum orientations, energy
separation between the partner bands, and behavior of electromagnetic
transitions, for the first time we find aplanar rotation or equivalently chiral
geometry beyond the usual one proton and one neutron hole coupled with a
triaxial rotor.Comment: 25 pages, 10 figures, accepted for publication in Physical Review
Entropy and Its Quantum Thermodynamical Implication for Anomalous Spectral Systems
The state function entropy and its quantum thermodynamical implication for
two typical dissipative systems with anomalous spectral densities are studied
by investigating on their low-temperature quantum behavior. In all cases it is
found that the entropy decays quickly and vanishes as the temperature
approaches zero. This reveals a good conformity with the third law of
thermodynamics and provides another evidence for the validity of fundamental
thermodynamical laws in the quantum dissipative region.Comment: 10 pages, 3 figure
Superconductivity induced by doping Rh in CaFe2-xRhxAs2
In this paper we report the synthesis of iron-based superconductors
CaFe2-xRhxAs2 using one-step solid state reaction method, which crystallizes in
the ThCr2Si2-type structure with a space group I4/mmm. The systematic evolution
of the lattice constants demonstrates that the Fe ions are successfully
replaced by the Rh. By increasing the doping content of Rh, the
spin-density-wave (SDW) transition in the parent compound is suppressed and
superconductivity emerges. The maximum superconducting transition temperature
is found at 18.5 K with the doping level of x = 0.15. The temperature
dependence of DC magnetization confirms superconducting transitions at around
15 K. The general phase diagram was obtained and found to be similar to the
case of Rh-doping Sr122 system. Our results explicitly demonstrate the
feasibility of inducing superconductivity in Ca122 compounds by higher
d-orbital electrons doping, however, different Rh-doping effect between FeAs122
compounds and FeAs1111 systems still remains an open question.Comment: 15 pages, 6 figure
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