Rikio Settai

High-field state of the flux-line lattice in the unconventional superconductor CeCoIn5

Ultrasound velocity measurements of the unconventional superconductor CeCoIn_5 with extremely large Pauli paramagnetic susceptibility reveal an unusual structural transformation of the flux line lattice (FLL) in the vicinity of the upper critical field. The transition field coincides with that at which heat capacity measurements reveal a second order phase transition. The lowering of the sound velocity at the transition is consistent with the collapse of the FLL tilt modulus and a crossover to quasi two-dimensional FLL pinning. These results provide a strong evidence that the high field state is the Fulde-Ferrel-Larkin-Ovchinikov phase, in which the order parameter is spatially modulated and has planar nodes aligned perpendicular to the vortices.

Normal-state Hall Angle and Magnetoresistance in Quasi-2D Heavy Fermion CeCoIn5 near a Quantum Critical Point

The normal-state Hall effect and magnetoresisitance (MR) have been measured in the quasi two dimensional (2D) heavy fermion superconductor CeCoIn 5 . In the non-Fermi liquid region where the reistivity ρ x x exhibits an almost perfect T -linear dependence, the Hall angle varies as cot θ H ∝ T 2 and MR displays a strong violation of Kohlers rule. We demonstrate a novel relation between the MR and the Hall conductivity, Δρ x x /ρ x x ∝(σ x y ρ x x ) 2 . These results bear a striking resemblance to the normal-state properties of high- T c cuprates, indicating universal transport properties in the presence of quasi-2D antiferromagnetic fluctuations near a quantum critical point.The normal-state Hall effect and magnetoresisitance (MR) have been measured in the quasi-2D heavy fermion superconductor CeCoIn_5. In the non-Fermi liquid region where the reistivity rho_xx exhibits an almost perfect T-linear dependence, the Hall angle varies as cot theta_H propto T^2 and the MR displays a strong violation of Kohlers rule. We demonstrate a novel relation between the MR and the Hall conductivity, Delta rho_xx/rho_xx propto (sigma_xy rho_xx)^2. These results bear a striking resemblance to the normal-state properties of high-T_c cuprates, indicating universal transport properties in the presence of quasi-2D antiferromagnetic fluctuations near a quantum critical point.

Differential Paramagnetic Effect of Non-Centrosymmetric Superconductor LaPt3Si

We report the superconducting properties of LaPt 3 Si poly and single crystals with non-centrosymmetric structure. We have measured ac magnetic susceptibility, χ ac = χ + iχ, under sweeping magnetic fields. On the χ, a peak ascribed to the differential paramagnetic effect DPE is observed just below critical fields, where the superconducting state of LaPt 3 Si collapses completely by an external magnetic field. However this DPE behavior disappears below 0.40 K. Additionally, in this temperature range, the width of the magnetic field of collapsing superconductivity becomes broader and the superconducting domains survive even in higher magnetic fields.

Neutron Scattering Study on High-Quality Single Crystals of Non-Centrosymmetric Heavy-Fermion Superconductor CePt3Si

In order to get detailed insights into magnetism and its relationship with superconductivity, neutron scattering experiments were carried out on high-quality single crystals of the non-centrosymmetric heavy-fermion superconductor CePt 3 Si, with T N =2.2 K and T sc ∼0.45 K. All the samples used in this study were characterised via specific heat measurements. Sharp specific heat jumps at T sc =0.45 K, and T N =2.2 K for all samples prove the high quality of the crystal.The neutron diffraction study confirms that an antiferromagnetic peak described with the propagation vector q =(0,0,1/2) persists inside the superconducting state, with a tiny suppression of the magnetic intensity below T sc . In contrast, an external magnetic field along the [001] direction causes a drastic change in the antiferromagnetic state; the antiferromagnetic intensity shows an enormous enhancement with increasing applied field. The magnetic intensity does not show any anomaly at B c2 , instead there exists a small inflection at aro...

Phase diagram for antiferromagnetism and superconductivity in the pressure-induced heavy-fermion superconductor Ce2RhIn8 probed by 115In-NQR

We present a novel phase diagram for the antiferromagnetism and superconductivity in Ce

Superconducting Properties and de Haas-van Alphen Effect in CeCo2 Single Crystal

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Search for Spontaneous Magnetization of Superconductors with Broken Time-Reversal Symmetry

RhIn

Transport Properties of UT2Zn20 (T: Co, Ir)

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Precise Thermal Expansion Measurements on Heavy Fermion Compounds YbT2Zn20(T: Co, Rh, Ir)

probed by In-NQR studies under pressure (

Drastic Change of Electronic Properties in Ce2MgSi2 and CeNiIn4 under High Pressure

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