Searcharxiv⌕ Search

arXiv subjects

T. Kondo

Publications and source records attributed to T. Kondo.

43 records · Page 3Linked to original sources
arXiv2005

High-energy spectroscopic study of the III-V nitride-based diluted magnetic semiconductor Ga$_{1-x}$Mn$_{x}$N

We have studied the electronic structure of the diluted magnetic semiconductor Ga$_{1-x}$Mn$_{x}$N ($x$ = 0.0, 0.02 and 0.042) grown on Sn-doped $n$-type GaN using photoemission and soft x-ray absorption spectroscopy. Mn $L$-edge x-ray absorption have indicated that the Mn ions are in the tetrahedral crystal field and that their valence is divalent. Upon Mn doping into GaN, new state were found to form within the band gap of GaN, and the Fermi level was shifted downward. Satellite structures in the Mn 2$p$ core level and the Mn 3$d$ partial density of states were analyzed using configuration-interaction calculation on a MnN$_{4}$ cluster model. The deduced electronic structure parameters reveal that the $p$-$d$ exchange coupling in Ga$_{1-x}$Mn$_{x}$N is stronger than that in Ga$_{1-x}$Mn$_{x}$As.

cond-mat.mtrl-sci↗
arXiv2004

Magnetization measurements on Li2Pd3B superconductor

Magnetization in DC magnetic fields and at different temperatures have been measured on the Li2Pd3B compound. This material was recently found to show superconductivity at 7-8K. Critical fields Hc1(0) and Hc2(0) have been determined to be 135Oe and 4T, respectively. Critical current density, scaling of the pinning force within the Kramer model and the irreversibility field data are presented. Several superconductivity parameters were deduced: x(csi)=9.1 nm, l(lamda)=194nm and k=21. The material resembles other boride superconductors from the investigated points of view.

cond-mat.supr-con↗
arXiv2002

Fermion Mass Hierarchy in Six Dimensional SO(10) Grand Unified Theory on a $T^2/Z_2$ Orbifold

We suggest a simple supersymmetric SO(10) grand unified theory in 6 dimensions which produces the suitable fermion mass hierarchies. The 5th and 6th dimensional coordinates are compactified on a $T^2/Z_2$ orbifold. The gauge and Higgs fields propagate in 6 dimensions while ordinal chiral matter fields are localized in 4 dimensions. The orbifolding and boundary conditions realize the gauge symmetry reduction, $SU(3)_C\times SU(2)_L \times U(1)_Y \times U(1)_X$, and the triplet-doublet mass splitting. We introduce extra three sets of vector-like heavy fields: two sets propagate in 6 dimensions and chiral fields which couple to them are defined as the 1st generation, and one set propagates in 5 dimensions and chiral fields which couple to them are defined as the 2nd generation. The suitable fermion mass hierarchies are generated by integrating out these vector-like heavy fields.

hep-ph↗
arXiv2002

Fermion Mass Hierarchy in 6 dimensional SO(10) SUSY GUT

We suggest simple models which produce the suitable fermion mass hierarchies and flavor mixing angles based on the supersymmetric SO(10) grand unified theory in 6 dimensions compactified on a T^2/Z_2 orbifold. The gauge and Higgs fields propagate in 6 dimensions while ordinal chiral matter fields are localized in 4 dimensions. We introduce extra vector-like heavy fields in the extra dimensions. We show three models according to the configurations of vector-like fields in extra dimensions. The suitable fermion mass hierarchies and flavor mixings are generated by integrating out these vector-like heavy fields.

hep-ph↗
arXiv2001

Model with Gauge Coupling Unification on $S^1/(Z_2 \times Z_2')$ Orbifold

We suggest a simple grand unified theory where the fifth dimensional coordinate is compactified on an $S^1/(Z_2 \times Z_2')$ orbifold. This model contains additional ${\bf 10 + \overline{10}}$, (${\bf 15 + \overline{15}}$) and two ${\bf 24}$ Higgs multiplets in the non-supersymmetric SU(5) grand unified theory. Although this model is non-supersymmetric theory, the gauge coupling unification is realized due to the mass splittings of Higgs multiplets by $S^1/(Z_2 \times Z_2')$ orbifolding. The constraints from the $b \to s γ$, $μ\to e γ$, and electron and muon anomalous magnetic moments are also discussed.

hep-ph↗
arXiv2000

Superconducting Fluctuations and the Pseudogap in the Slightly-overdoped High-Tc Superconductor TlSr2CaCu2O6.8: High Magnetic Field NMR Studies

From measurements of the ^{63}Cu Knight shift (K) and the nuclear spin-lattice relaxation rate (1/T_{1}) under magnetic fields from zero up to 28 T in the slightly overdoped superconductor TlSr_{2}CaCu_{2}O_{6.8} (T_{c}=68 K), we find that the pseudogap behavior, {\em i.e.}, the reductions of 1/T_{1}T and K above T_{c} from the values expected from the normal state at high T, is strongly field dependent and follows a scaling relation. We show that this scaling is consistent with the effects of the Cooper pair density fluctuations. The present finding contrasts sharply with the pseudogap property reported previously in the underdoped regime where no field effect was seen up to 23.2 T. The implications are discussed.

cond-mat.supr-con↗