New Superconducting and Magnetic Phases Emerge on the Verge of Antiferromagnetism in CeIn3_3

We report the discovery of new superconducting and novel magnetic phases in CeIn$_3$ on the verge of antiferromagnetism (AFM) under pressure ($P$) through the In-nuclear quadrupole resonance (NQR) measurements. We have found a $P$-induced phase separation of AFM and paramagnetism (PM) without any trace for a quantum phase transition in CeIn$_3$. A new type of superconductivity (SC) was found in $P=2.28-2.5$ GPa to coexist with AFM that is magnetically separated from PM where the heavy fermion SC takes place. We propose that the magnetic excitations such as spin-density fluctuations induced by the first-order magnetic phase transition might mediate attractive interaction to form Cooper pairs.Comment: 4 pages, 4 EPS figures, submitted to J. Phys. Soc. Jp

A Study of Gaussianity in CMB band maps

The detection of non-Gaussianity in the CMB data would rule out a number of inflationary models. A null detection of non-Gaussianity, instead, would exclude alternative models for the early universe. Thus, a detection or non-detection of primordial non-Gaussianity in the CMB data is crucial to discriminate among inflationary models, and to test alternative scenarios. However, there are various non-cosmological sources of non-Gaussianity. This makes important to employ different indicators in order to detect distinct forms of non-Gaussianity in CMB data. Recently, we proposed two new indicators to measure deviation from Gaussianity on large angular scales, and used them to study the Gaussianity of the raw band WMAP maps with and without the KQ75 mask. Here we extend this work by using these indicators to perform similar analyses of deviation from Gaussianity of the foreground-reduced Q, V, and W band maps. We show that there is a significant deviation from Gaussianity in the considered full-sky maps, which is reduced to a level consistent with Gaussianity when the KQ75 mask is employed.Comment: 5 pages, 2 PS figures, uses ws-ijmpd.cls ; to be published in the International Journal of Modern Physics

Gapless Magnetic and Quasiparticle Excitations due to the Coexistence of Antiferromagnetism and Superconductivity in CeRhIn5_5 : A study of 115^{115}In-NQR under Pressure

We report systematic measurements of ac-susceptibility, nuclear-quadrupole-resonance spectrum, and nuclear-spin-lattice-relaxation time ($T_1$) on the pressure ($P$)- induced heavy-fermion (HF) superconductor CeRhIn$_5$. The temperature ($T$) dependence of $1/T_1$ at $P$ = 1.6 GPa has revealed that antiferromagnetism (AFM) and superconductivity (SC) coexist microscopically, exhibiting the respective transition at $T_N = 2.8$ K and $T^{MF}_c$ = 0.9 K. It is demonstrated that SC does not yield any trace of gap opening in low-lying excitations below $T_c^{onset} = 2$ K, but $T_c^{MF} = 0.9$ K, followed by a $T_1T$ = const law. These results point to the unconventional characteristics of SC coexisting with AFM. We highlight that both of the results deserve theoretical work on the gapless nature in low-lying excitation spectrum due to the coexistence of AFM and SC and the lack of the mean-field regime below $T_c^{onset} = 2$ K.Comment: 4pages,5figures,revised versio

General treatment of isocurvature perturbations and non-Gaussianities

We present a general formalism that provides a systematic computation of the linear and non-linear perturbations for an arbitrary number of cosmological fluids in the early Universe going through various transitions, in particular the decay of some species (such as a curvaton or a modulus). Using this formalism, we revisit the question of isocurvature non-Gaussianities in the mixed inflaton-curvaton scenario and show that one can obtain significant non-Gaussianities dominated by the isocurvature mode while satisfying the present constraints on the isocurvature contribution in the observed power spectrum. We also study two-curvaton scenarios, taking into account the production of dark matter, and investigate in which cases significant non-Gaussianities can be produced.Comment: Substantial improvements with respect to the first version. In particular, we added a discussion on the confrontation of the models with future observational data. This version is accepted for publication in JCA

Coexistence of Superconductivity and Antiferromagnetism in Heavy-Fermion Superconductor CeCu_{2}(Si_{1-x}Ge_{x})_{2} Probed by Cu-NQR --A Test Case for the SO(5) Theory--

We report on the basis of Cu-NQR measurements that superconductivity (SC) and antiferromagnetism (AF) coexist on a microscopic level in CeCu_{2}(Si_{1-x}Ge_{x})_{2}, once a tiny amount of 1%Ge (x = 0.01) is substituted for Si. This coexistence arises because Ge substitution expands the unit-cell volume in nearly homogeneous CeCu2Si2 where the SC coexists with slowly fluctuating magnetic waves. We propose that the underlying exotic phases of SC and AF in either nearly homogeneous or slightly Ge substituted CeCu2Si2 are accountable based on the SO(5) theory that unifies the SC and AF. We suggest that the mechanism of the SC and AF is common in CeCu2Si2.Comment: 7 pages with 6 figures embedded in the text. To be published in J. Phys. Condens. Matter, 200

Exotic superconductivity in the coexistent phase of antiferromagnetism and superconductivity in CeCu2(Si0.98Ge0.02)2: A Cu-NQR study under hydrostatic pressure

We report a pressure ($P$) effect on CeCu$_2$(Si$_{0.98}$Ge$_{0.02}$)$_2$ where an antiferromagnetic (AFM) order at $T_N \sim$ 0.75 K coexists with superconductivity below $T_c \sim$ 0.4 K\@. At pressures exceeding $P = 0.19$ GPa, the AFM order is suppressed, which demonstrates that the sudden emergence of AFM order due to the Ge doping is ascribed to the intrinsic lattice expansion. The exotic superconductivity at $P = 0$ GPa is found to evolve into a typical heavy-fermion one with a line-node gap above $P = 0.91$ GPa\@. We highlight that the anomalous enhancement in nuclear spin-lattice relaxation rate $1/T_1$ that follows a $T_1T$ = const. behavior well below $T_c$ at $P$ = 0 GPa is characterized by the persistence of low-lying magnetic excitations, which may be inherent to the coexistent state of antiferromagnetism and superconductivity.Comment: 5 pages with 4 figures embedded in the text. To be published in J. Phys. Soc. Jp