Extended Gross-Pitaevskii equations for the rotating F=2 condensate in a harmonic trap are solved both numerically and variationally using trial functions for each component of the wave function. Axially symmetric vortex solutions are analyzed and energies of polar and cyclic states are calculated. The equilibrium transitions between different phases with changing of the magnetization are studied. We show that at high magnetization the ground state of the system is determined by interaction in "density" channel, and at low magnetization spin interactions play a dominant role. Although there are five hyperfine states, all the particles are always condensed in one, two, or three states. Two interesting types of vortex structures are also discussed.
en-copyright= kn-copyright= en-aut-name=PogosovW V en-aut-sei=Pogosov en-aut-mei=W V kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KawateR en-aut-sei=Kawate en-aut-mei=R kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=MizushimaT en-aut-sei=Mizushima en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=MachidaK en-aut-sei=Machida en-aut-mei=K kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil= kn-affil=Okayama University affil-num=2 en-affil= kn-affil=Okayama University affil-num=3 en-affil= kn-affil=Okayama University affil-num=4 en-affil= kn-affil=Okayama University en-keyword=vortices kn-keyword=vortices END start-ver=1.4 cd-journal=joma no-vol=72 cd-vols= no-issue=5 article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2005 dt-pub=200511 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Multibranch Bogoliubov-Bloch spectrum of a cigar-shaped Bose condensate in an optical lattice en-subtitle= kn-subtitle= en-abstract= kn-abstract=We study properties of excited states of an array of weakly coupled quasi-two-dimensional Bose condensates by using the hydrodynamic theory. The spectrum of the axial excited states strongly depends on the coupling among the various discrete radial modes in a given symmetry. By including mode coupling within a given symmetry, the complete excitation spectrum of axial quasiparticles with various discrete radial nodes are presented. A single parameter which determines the strength of the mode coupling is identified. The excitation spectrum in the zero angular momentum sector can be observed by using the Bragg scattering experiments.
en-copyright= kn-copyright= en-aut-name=GhoshTarun Kanti en-aut-sei=Ghosh en-aut-mei=Tarun Kanti kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MachidaK. en-aut-sei=Machida en-aut-mei=K. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil= kn-affil=Okayama University affil-num=2 en-affil= kn-affil=Okayama University en-keyword=einstein kn-keyword=einstein en-keyword=condensate kn-keyword=condensate en-keyword=superfluid kn-keyword=superfluid en-keyword=arrays kn-keyword=arrays en-keyword=atoms kn-keyword=atoms en-keyword=wave kn-keyword=wave en-keyword=gas kn-keyword=gas END start-ver=1.4 cd-journal=joma no-vol=74 cd-vols= no-issue=2 article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2006 dt-pub=20068 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Cyclic phase in f=2 spinor condensate:long-range order, kinks, and roughening transition en-subtitle= kn-subtitle= en-abstract= kn-abstract=We study the effect of thermal fluctuations on homogeneous infinite Bose-Einstein condensate with spin F=2 in the cyclic state, when atoms occupy three hyperfine states with m(F)=0,+/- 2. We use both the approach of small-amplitude oscillations and mapping of our model on the sine-Gordon model. We show that thermal fluctuations lead to the existence of the rough phase in one- and two-dimensional systems, when the presence of kinks is favorable. The structure and energy of a single kink are found. We also discuss the effect of thermal fluctuations on spin degrees of freedom in F=1 condensate.
en-copyright= kn-copyright= en-aut-name=PogosovW V en-aut-sei=Pogosov en-aut-mei=W V kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MachidaK en-aut-sei=Machida en-aut-mei=K kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil= kn-affil=Okayama University affil-num=2 en-affil= kn-affil=Okayama University en-keyword=bose-einstein condensate kn-keyword=bose-einstein condensate en-keyword=dynamics kn-keyword=dynamics en-keyword=gases kn-keyword=gases END start-ver=1.4 cd-journal=joma no-vol=74 cd-vols= no-issue=2 article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2006 dt-pub=20068 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Thermal fluctuations of vortex clusters in quasi-two-dimensional bose-einstein condensates en-subtitle= kn-subtitle= en-abstract= kn-abstract=We study the thermal fluctuations of vortex positions in small vortex clusters in a harmonically trapped rotating Bose-Einstein condensate. It is shown that the order-disorder transition of two-shell clusters occurs via the decoupling of shells with respect to each other. The corresponding "melting" temperature depends strongly on the commensurability between numbers of vortices in shells. We show that melting can be achieved at experimentally attainable parameters and very low temperatures. Also studied is the effect of thermal fluctuations on vortices in an anisotropic trap with small quadrupole deformation. We show that thermal fluctuations lead to the decoupling of a vortex cluster from the pinning potential produced by this deformation. The decoupling temperatures are estimated and strong commensurability effects are revealed.
en-copyright= kn-copyright= en-aut-name=PogosovW V en-aut-sei=Pogosov en-aut-mei=W V kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MachidaK en-aut-sei=Machida en-aut-mei=K kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil= kn-affil=Okayama University affil-num=2 en-affil= kn-affil=Okayama University en-keyword=scissors mode kn-keyword=scissors mode en-keyword=gas kn-keyword=gas en-keyword=superfluidity kn-keyword=superfluidity en-keyword=transition kn-keyword=transition en-keyword=stability kn-keyword=stability en-keyword=phase kn-keyword=phase END start-ver=1.4 cd-journal=joma no-vol=94 cd-vols= no-issue=6 article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2005 dt-pub=20052 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Anisotropic diamagnetic response in type-II superconductors with gap and fermi-surface anisotropies en-subtitle= kn-subtitle= en-abstract= kn-abstract=The effects of anisotropic gap structures on a diamagnetic response are investigated in order to demonstrate that the field-angle-resolved magnetization [M-L (chi)] measurement can be used as a spectroscopic method to detect gap structures. Our microscopic calculation based on the quasiclassical Eilenberger formalism reveals that M-L (chi) in a superconductor with a fourfold gap displays a fourfold oscillation reflecting the gap and Fermi-surface anisotropies, and the sign of this oscillation changes at a field between H-c1 and H-c2. As a prototype of unconventional superconductors, magnetization data for borocarbides are also discussed.
en-copyright= kn-copyright= en-aut-name=AdachiH en-aut-sei=Adachi en-aut-mei=H kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MiranovicP en-aut-sei=Miranovic en-aut-mei=P kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=IchiokaM en-aut-sei=Ichioka en-aut-mei=M kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=MachidaK en-aut-sei=Machida en-aut-mei=K kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil= kn-affil=Okayama University affil-num=2 en-affil= kn-affil=University of Montenegro affil-num=3 en-affil= kn-affil=Okayama University affil-num=4 en-affil= kn-affil=Okayama University en-keyword=ginzburg-landau equations kn-keyword=ginzburg-landau equations en-keyword=density-of-states kn-keyword=density-of-states en-keyword=virial-theorem kn-keyword=virial-theorem en-keyword=magnetization kn-keyword=magnetization en-keyword=dependence kn-keyword=dependence en-keyword=symmetry kn-keyword=symmetry en-keyword=luni2b2c kn-keyword=luni2b2c en-keyword=yni2b2c kn-keyword=yni2b2c END start-ver=1.4 cd-journal=joma no-vol=72 cd-vols= no-issue=6 article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2005 dt-pub=20058 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Carbon-substitution dependent multiple superconducting gap of MgB2: A sub-meV resolution photoemission study en-subtitle= kn-subtitle= en-abstract= kn-abstract="Sub-meV" resolution photoemission spectroscopy was used to study carbon-substitution dependence of the multiple superconducting gap of Mg(B1-xCx)(2). Two features corresponding to sigma and pi gaps are clearly observed in the raw spectra up to carbon concentration x=0.075. The observed x dependence of the two gaps shows a qualitatively different behavior: the sigma gap is proportional to T-c while the pi gap shows negligible change. Doping as well as temperature dependence can be explained within the two-band mean-field theory. Implications from the present study are discussed.
en-copyright= kn-copyright= en-aut-name=TsudaS en-aut-sei=Tsuda en-aut-mei=S kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YokoyaT en-aut-sei=Yokoya en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KissT en-aut-sei=Kiss en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=ShimojimaT en-aut-sei=Shimojima en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=ShinS en-aut-sei=Shin en-aut-mei=S kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=TogashiT en-aut-sei=Togashi en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=WatanabeS en-aut-sei=Watanabe en-aut-mei=S kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=ZhangC en-aut-sei=Zhang en-aut-mei=C kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=ChenC T en-aut-sei=Chen en-aut-mei=C T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=LeeS en-aut-sei=Lee en-aut-mei=S kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=UchiyamaH en-aut-sei=Uchiyama en-aut-mei=H kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=TajimaS en-aut-sei=Tajima en-aut-mei=S kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= en-aut-name=NakaiN en-aut-sei=Nakai en-aut-mei=N kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=13 ORCID= en-aut-name=MachidaK en-aut-sei=Machida en-aut-mei=K kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=14 ORCID= affil-num=1 en-affil= kn-affil=University of Tokyo affil-num=2 en-affil= kn-affil=University of Tokyo affil-num=3 en-affil= kn-affil=Institute of Physical and Chemical Research affil-num=4 en-affil= kn-affil=University of Tokyo affil-num=5 en-affil= kn-affil=University of Tokyo affil-num=6 en-affil= kn-affil=Institute of Physical and Chemical Research affil-num=7 en-affil= kn-affil=University of Tokyo affil-num=8 en-affil= kn-affil=Beijing Center for Crystal R&D affil-num=9 en-affil= kn-affil=Beijing Center for Crystal R&D affil-num=10 en-affil= kn-affil=International Superconductivity Technology Center affil-num=11 en-affil= kn-affil=International Superconductivity Technology Center affil-num=12 en-affil= kn-affil=International Superconductivity Technology Center affil-num=13 en-affil= kn-affil=Kyoto University affil-num=14 en-affil= kn-affil=Okayama University en-keyword=magnesium diboride kn-keyword=magnesium diboride en-keyword=single-crystals kn-keyword=single-crystals en-keyword=origin kn-keyword=origin en-keyword=boron kn-keyword=boron END start-ver=1.4 cd-journal=joma no-vol=97 cd-vols= no-issue=12 article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2006 dt-pub=20069 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Generic phase diagram of fermion superfluids with population imbalance en-subtitle= kn-subtitle= en-abstract= kn-abstract=It is shown by microscopic calculations for trapped imbalanced Fermi superfluids that the gap function always has sign changes, i.e., the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like state, up to a critical imbalance P-c, beyond which normal state becomes stable, at temperature T=0. A temperature-versus-pressure phase diagram is constructed, where the BCS state without sign change is stable only at T not equal 0. We reproduce the observed bimodality in the density profile to identify its origin and evaluate P-c as functions of T and the coupling strength. These dependencies match with the recent experiments.
en-copyright= kn-copyright= en-aut-name=MachidaK en-aut-sei=Machida en-aut-mei=K kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MizushimaT en-aut-sei=Mizushima en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=IchiokaM en-aut-sei=Ichioka en-aut-mei=M kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil= kn-affil=Okayama University affil-num=2 en-affil= kn-affil=Okayama University affil-num=3 en-affil= kn-affil=Okayama University en-keyword=molecular-field kn-keyword=molecular-field en-keyword=superconductivity kn-keyword=superconductivity en-keyword=gas kn-keyword=gas END