Nobuyuki Kurita

Fermi Surface and Mass Enhancement in KFe2As2 from de Haas-van Alphen Effect Measurements

We report on a band structure calculation and de Haas–van Alphen measurements of KFe 2 As 2 . Three cylindrical Fermi surfaces are found. Effective masses of electrons range from 6 to 18 m e , m e being the free electron mass. Remarkable discrepancies between the calculated and observed Fermi surface areas and the large mass enhancement (\({\gtrsim}3\)) highlight the importance of electronic correlations in determining the electronic structures of iron pnicitide superconductors.

Complete Fermi surface in BaFe2As2 observed via Shubnikov-de Haas oscillation measurements on detwinned single crystals.

We show that the Fermi surface (FS) in the antiferromagnetic phase of BaFe(2)As(2) is composed of one hole and two electron pockets, all of which are three dimensional and closed, in sharp contrast to the FS observed by angle-resolved photoemission spectroscopy. Considerations on the carrier compensation and Sommerfeld coefficient rule out existence of unobserved FS pockets of significant sizes. A standard band structure calculation reasonably accounts for the observed FS, despite the overestimated ordered moment. The mass enhancement, the ratio of the effective mass to the band mass, is 2-3.

Determination of the Upper Critical Field of a Single Crystal LiFeAs: The Magnetic Torque Study up to 35 Tesla

We report on the upper critical field B_c2 of a superconducting LiFeAs single crystal with T_c~16 K, determined from magnetic torque measurements in dc-magnetic fields up to 35 T and at temperatures down to 0.3 K. B_c2 at 0.3 K is obtained to be 26.4 T and 15.5 T for the applied field B_a||ab and B_a||c, respectively. The anisotropy parameter

Phase diagram of pressure-induced superconductivity in EuFe2As2probed by high-pressure resistivity up to 3.2 GPa

\Gamma

On the Mechanism of the Spin State Transition of (Pr1-ySmy)1-xCaxCoO3

=

Magnetization process and collective excitations in the S=1/2 triangular-lattice Heisenberg antiferromagnet Ba3CoSb2O9.

B_c2^ab / B_c2^c

Fermi surface in KFe2As2determined via de Haas–van Alphen oscillation measurements

is ~ 3 at T_c and decreases to 1.7 as

Magnetic phase diagram of theS=12triangular-lattice Heisenberg antiferromagnetBa3CoNb2O9

T \rightarrow 0

Vortex Dynamics and Diamagnetic Torque Signals in Two Dimensional Organic Superconductor λ-(BETS)2GaCl4

, showing rather isotropic superconductivity. While B_c2 is orbitally-limited for B_a||c, the spin-paramagnetic effect is evident in the temperature dependence of B_c2 for B_a||ab

Orbital Effect on FFLO Phase and Energy Dissipation due to Vortex Dynamics in Magnetic-Field-Induced Superconductor λ-(BETS)2FeCl4

We have constructed a pressure