We report a genuine phase diagram for a disorder-free CuO 2 plane based on the precise evaluation of the local hole density (N h ) by site-selective Cu-NMR studies on five-layered high-T c cuprates. It has been unraveled that (1) the antiferromagnetic metallic state (AFMM) is robust up to N h % 0:17, (2) the uniformly mixed phase of superconductivity (SC) and AFMM is realized at N h 0:17, (3) the tetracritical point for the AFMM/(AFMM+SC)/SC/PM (paramagnetism) phases may be present at N h % 0:15 and T % 75 K, (4) T c is maximum close to a quantum critical point (QCP) at which the AFM order collapses, suggesting the intimate relationship between the high-T c SC and the AFM order. The results presented here strongly suggest that the AFM interaction plays the vital role as the glue for the Cooper pairs, which will lead us to a genuine understanding of why the T c of cuprate superconductors is so high.

We study heavy baryons with an exotic flavor quantum number formed by a heavy meson and a nucleon ( " DN and BN) through a long range one pion exchange interaction. The bound state found previously in the ðI; J P Þ ¼ ð0; 1=2 À Þ channel survives when short range interaction is included. In addition, we find a resonant state with ðI; J P Þ ¼ ð0; 3=2 À Þ as a Feshbach resonance predominated by a heavy vector meson and a nucleon ( " D Ã N and B Ã N). We find that these exotic states exist for the charm and heavier flavor region.

We consider a uniform dipolar Fermi gas in two-dimensions (2D) where the dipole moments of fermions are aligned by an orientable external field. We obtain the ground state of the gas in HartreeFock approximation and investigate RPA stability against density fluctuations of finite momentum. It is shown that the density wave instability takes place in a broad region where the system is stable against collapse. We also find that the critical temperature can be a significant fraction of Fermi temperature for a realistic system of polar molecules.

Photoluminescence ͑PL͒ properties of heavily P-and B-doped Si nanocrystals ͑nc-Si͒ are studied. By simultaneously doping two types of impurities, nc-Si exhibit strong PL at around 0.9 eV at room temperature. The temperature quenching of the PL is very small. Although the PL peak energy is very close to that of dangling-bond related PL previously observed, all of the observed properties, i.e., decay dynamics, degree of temperature quenching, etc., are apparently different. The transition between donor and acceptor states in nc-Si is the possible origin of the low-energy PL.

The effects of B and P codoping on photoluminescence (PL) properties of Si nanocrystals (nc-Si) are studied systematically. It is shown that the PL intensity of codoped nc-Si is always higher than that of either P-or B-doped nc-Si. The intensity is sometimes even higher than that of pure nc-Si at relatively low P and B concentrations and low annealing temperatures. By doping P and B simultaneously to very high concentrations, the PL peak shifts below the band gap of bulk Si.

資源タイプ Resource TypeJournal Article / 学術雑誌論文 版区分 Resource Version publisher権利 Rights

We study exotic mesons with double charm and bottom flavor, whose quark configuration is \bar{Q}\bar{Q}qq. This quark configuration has no annihilation process of quark and antiquark, and hence is a genuinely exotic states. We take a hadronic picture by considering the molecular states composed of a pair of heavy mesons, such as DD, DD* and D*D* for charm flavor, and BB, BB* and B*B* for bottom flavor. The interactions between heavy mesons are derived from the heavy quark effective theory. All molecular states are classified by I(J^P) quantum numbers, and are systematically studied up to the total angular momentum J \leq 2. By solving the coupled channel Schrodinger equations, due to the strong tensor force of one pion exchanging, we find bound and/or resonant states of various quantum numbers.Comment: 24 pages, 3 figure

Current studies on heavy hadrons in nuclear medium are reviewed with a summary of the basic theoretical concepts of QCD, namely chiral symmetry, heavy quark spin symmetry, and the effective Lagrangian approach. The nuclear matter is an interesting place to study the properties of heavy hadrons from many different points of view. We emphasize the importance of the following topics: (i) charm/bottom hadron-nucleon interaction, (ii) structure of charm/bottom nuclei, and (iii) QCD vacuum properties and hadron modifications in nuclear medium. We pick up three different groups of heavy hadrons, quarkonia (J/ψ, Υ), heavy-light mesons (D/D,B/B) and heavy baryons (Λ c , Λ b ). The modifications of those hadrons in nuclear matter provide us with important information to investigate the essential properties of heavy hadrons. We also give the discussions about the heavy hadrons, not only in infinite nuclear matter, but also in finite-size atomic nuclei with finite baryon numbers, to serve future experiments. but it is "renormalized" to the low energy degrees of freedom such as the collective modes (e.g. surface vibration, rotation, nucleon pairings) [9].2 We notice that, for the light u and d flavors, the first excited state of the nucleon, N (1535) with spin-parity J P = 1/2 − , is well explained as an orbital excitation of valence quarks (P-wave excitation), but with an s quark the corresponding state, Λ(1405) with J P = 1/2 − , shows up with very different structure governed by theKN -πΣ dynamics.4 See for example Ref. [28]. 5 This is an example of the quantum fluctuations, which are important in the state with finite baryon number density.Such fluctuation effect is suppressed at finite temperature. 6 The Kondo effect is a known phenomena caused by the Fermi instability when the heavy impurity particle with non-Abelian interaction exists (see Sect. 4).(j ) J with total spin J and brown muck spin j decays to the final heavy hadron Ψ (j) J with total spin J and brown muck spin j by emitting a light hadron, e.g. a pion π with relative angular momentum L. Due to the independent conservations of the heavy quark spin S and the brown muck spin j, we see that the strength of the decay widths is parametrized as(2.2.45) by neglecting the corrections with the heavy hadron mass M [57]. Here J ( ) = j ( ) ± 1/2. In realistic application to experimental data, we need to include the phase space factor due to the different mass thresholds. Including this factor, we can reproduce the branching ratios of the known decay patterns of 8 We notice the conservation of J is valid only when the vacuum is rotationally invariant. If the rotational symmetry is broken, we cannot apply the following discussion. For example, such situation can happen when the external field (e.g. a magnetic field [56]) breaks the rotational symmetry.11 Note that the notations are different from those in Sect. 2.3.1 as fπ = √ 2F , ξ = u, V µ = −a µ , A µ = −a µ ⊥ and Uq = h. 12 We note that the covariant derivative forqQ meson is defined by D µ Hv = ∂ µ Hv + iHvV µ [26]...