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Register a new userLow-energy magnetic response of the noncentrosymmetric heavy-fermion superconductor CePt3Si studied via inelastic neutron scattering
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The low-energy magnetic excitations of the noncentrosymmetric heavy-fermion superconductor CePt3Si have been measured with inelastic neutron scattering on a single crystal. Kondo-type spin fluctuations with an anisotropic wave vector dependence are observed in the paramagnetic state. These fluctuations do not survive in the antiferromagnetically ordered state below TN=2.2 K but are replaced by damped spin waves, whose dispersion is much stronger along the c-axis than in other directions. No change is observed in the excitation spectrum or the magnetic order as the system enters the superconducting state below Tc=0.7 K.
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Nuclear quadrupole resonance (NQR) measurements were performed on the heavy fermion superconductor Ce3PtIn11 with Tc = 0.32 K. The temperature dependence of both spin-lattice relaxation rate 1/T1 and NQR spectra evidences the occurrence of two successive magnetic transitions with TN1 = 2.2 K and TN2 = 2.0 K. In successive magnetic transitions, even though the magnetic moment at the Ce(2) site plays a major role, the magnetic moment at the Ce(1) site also contributes to some extent. While a commensurate antiferromagnetic ordered state appears for TN2 < T < TN1, a partially incommensurate antiferromagnetic ordered state is suggested for T < TN2.
The superconducting order parameter of the first heavy-fermion superconductor CeCu2Si2 is currently under debate. A key ingredient to understand its superconductivity and physical properties is the quasiparticle dispersion and Fermi surface, which remains elusive experimentally. Here we present measurements from angle-resolved photoemission spectroscopy. Our results emphasize the key role played by the Ce 4f electrons for the low-temperature Fermi surface, highlighting a band-dependent conduction-f electron hybridization. In particular, we find a very heavy quasi-two-dimensional electron band near the bulk X point and moderately heavy three-dimensional hole pockets near the Z point. Comparison with theoretical calculations reveals the strong local correlation in this compound, calling for further theoretical studies. Our results provide the electronic basis to understand the heavy fermion behavior and superconductivity; implications for the enigmatic superconductivity of this compound are also discussed.
We report detailed very low temperature resistivity measurements on the heavy fermion compounds Ce_{1-x}La_{x}CoIn5 (x=0 and x=0.01), with current applied in two crystallographic directions [100] (basal plane) and [001] (perpendicular to the basal plane) under magnetic field applied in the [001] or [011] direction. We found a Fermi liquid (rho propto T^{2}) ground state, in all cases, for fields above the superconducting upper critical field. We discuss the possible location of a field induced quantum critical point with respect to Hc2(0), and compare our measurements with the previous reports in order to give a clear picture of the experimental status on this long debated issue.
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Field-angle dependent specific heat measurement has been done on the heavy-fermion superconductor CeCoIn5 down to ~ 0.29 K, in a magnetic field rotating in the tetragonal c-plane. A clear fourfold angular oscillation is observed in the specific heat with the minima (maxima) occurring along the [100] ([110]) directions. Oscillation persists down to low fields H << Hc2, thus directly proving the existence of gap nodes. The results indicate that the superconducting gap symmetry is most probably of dxy type.
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