WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
Browse
22 results
Search Results
Now showing 1 - 10 of 22
Article Citation - WoS: 150Citation - Scopus: 7Correlation of Tunneling Spectra in Bi2sr2cacu2o8+? With the Resonance Spin Excitation(American Physical Society, 2001) Zasadzinski, John F.; Özyüzer, Lütfi; Miyakawa, Nobuaki; Gray, Kenneth E.; Hinks, David G.; Kendziora, Christopher A.New break-junction tunneling data are reported in Bi2Sr2CaCu2O8+δ over a wide range of hole concentration from underdoped (Tc=74k) to optimal doped (Tc=95k) to overdoped (Tc=48k). The conductances exhibit sharp dips at a voltage, Ω/e, measured with respect to the superconducting gap. Clear trends are found such that the dip strength is maximum at optimal doping and that Ω scales as 4.9kTc over the entire doping range. These features link the dip to the resonance spin excitation and suggest quasiparticle interactions with this mode are important for superconductivity.Article Citation - WoS: 9Citation - Scopus: 10Doubly Charged Higgsinos at the Tevatron(American Physical Society, 2009) Demir, Durmuş Ali; Frank, Mariana; Ghosh, Dilip Kumar; Huitu, Katri; Rai, Santosh Kumar; Turan, İsmailSeveral supersymmetric models with extended gauge structures, motivated by either grand unification or by neutrino mass generation, predict light doubly charged Higgsinos. In this work we study the signals of doubly charged Higgsinos at the Tevatron in both pair- and single-production modes, and show that it is possible, especially from the events containing same-sign same-flavor isolated leptons, to disentangle the effects of doubly charged Higgsinos in the Tevatron data.Article Citation - WoS: 7Citation - Scopus: 8Search for Gauge Extensions of the Mssm at the Lhc(American Physical Society, 2009) Ahmed, Ali; Demir, Durmuş Ali; Frank, Mariana; Turan, İsmailThe extensions of the minimal supersymmetric model (MSSM), driving mainly from the need to solve the μ problem, involve novel matter species and gauge groups. These extended MSSM models can be searched for at the LHC via the effects of the gauge and Higgs bosons or their fermionic partners. Traditionally, the focus has been on the study of the extra forces induced by the new gauge and Higgs bosons present in such models. An alternative way of studying such effects is through the superpartners of matter species and the gauge forces. We thus consider a U(1)′ gauge extension of the MSSM, and perform an extensive study of the signatures of the model through the production and decays of the scalar quarks and gluino, which are expected to be produced copiously at the LHC. After a detailed study of the distinctive features of such models with regard to the signatures at the LHC, we carry out a detailed Monte-Carlo analysis of the signals from the process pp→nleptons+mjets+E T, and compare the resulting distributions with those predicted by the MSSM. Our results show that the searches for the extra gauge interactions in the supersymmetric framework can proceed not only through the forces mediated by the gauge and Higgs bosons but also through the superpartner forces mediated by the gauge and Higgs fermions. Analysis of the events induced by the squark/gluino decays presented here is complementary to the direct Z′ searches at the LHC.Article Citation - WoS: 35Citation - Scopus: 37Dirac Neutrino Masses From Generalized Supersymmetry Breaking(American Physical Society, 2008) Demir, Durmuş Ali; Everett, Lisa L.; Langacker, PaulWe demonstrate that Dirac neutrino masses in the experimentally preferred range are generated within supersymmetric gauge extensions of the standard model with a generalized supersymmetry breaking sector. If the superpotential neutrino Yukawa terms are forbidden by the gauge symmetry [such as a U(1)′], sub-eV scale effective Dirac mass terms can arise at tree level from hard supersymmetry breaking Yukawa couplings, or at one loop due to nonanalytic soft supersymmetry breaking trilinear scalar couplings. The radiative neutrino magnetic and electric dipole moments vanish at one-loop order.Article Citation - WoS: 13Citation - Scopus: 12Berry's Phase Under the Dzyaloshinskii-Moriya Interaction(American Physical Society, 2008) Kwan, M. K.; Gürkan, Zeynep Nilhan; Kwek, L. C.In this paper, we study the Dzyaloshinskii-Moriya (DM) anisotropic XX spin-chain model in the presence of an external homogeneous magnetic field. We found that the Berry phase of the system varies interestingly with small and large amounts of DM interaction and the magnetic field. In addition, we also considered the concurrence (i.e., the amount of entanglement) of the system, and the relationship between the concurrence and the Berry phase. Finally, we calculate the Berry phase of thermal states and verify that the results are consistent with that of the pure states.Article Citation - WoS: 1902Citation - Scopus: 2049Monolayer Honeycomb Structures of Group-Iv Elements and Iii-V Binary Compounds: First-Principles Calculations(American Physical Society, 2009) Şahin, Hasan; Cahangirov, Seymur; Topsakal, Mehmet; Bekaroğlu, Edip; Aktürk, Ethem; Senger, Ramazan Tuğrul; Çıracı, SalimUsing first-principles plane-wave calculations, we investigate two-dimensional (2D) honeycomb structure of group-IV elements and their binary compounds as well as the compounds of group III-V elements. Based on structure optimization and phonon-mode calculations, we determine that 22 different honeycomb materials are stable and correspond to local minima on the Born-Oppenheimer surface. We also find that all the binary compounds containing one of the first row elements, B, C, or N have planar stable structures. On the other hand, in the honeycomb structures of Si, Ge, and other binary compounds the alternating atoms of hexagons are buckled since the stability is maintained by puckering. For those honeycomb materials which were found stable, we calculated optimized structures, cohesive energies, phonon modes, electronic-band structures, effective cation and anion charges, and some elastic constants. The band gaps calculated within density functional theory using local density approximation are corrected by G W0 method. Si and Ge in honeycomb structure are semimetal and have linear band crossing at the Fermi level which attributes massless Fermion character to charge carriers as in graphene. However, all binary compounds are found to be semiconductor with band gaps depending on the constituent atoms. We present a method to reveal elastic constants of 2D honeycomb structures from the strain energy and calculate the Poisson's ratio as well as in-plane stiffness values. Preliminary results show that the nearly lattice matched heterostructures of these compounds can offer alternatives for nanoscale electronic devices. Similar to those of the three-dimensional group-IV and group III-V compound semiconductors, one deduces interesting correlations among the calculated properties of present honeycomb structures.Article Citation - WoS: 18Citation - Scopus: 18Squark Pair Production in the Mssm With Explicit Cp Violation(American Physical Society, 2007) Alan, Ahmet T.; Cankoçak, Kerem; Demir, Durmuş AliWe analyze effects of the CP-odd soft phases in the MSSM on the pair productions of colored superpartners in pp collisions at the LHC energies. We find that, among all pair-production processes, those of the scalar quarks in the first and second generations are particularly sensitive to the CP-odd phases, more precisely, to the phases of the gluinos and neutralinos. We compute pair-production cross sections, classify various production modes according to their dependencies on the gluino and neutralino phases, perform a detailed numerical analysis to determine individual as well as total cross sections, and give a detailed discussion of 2. electric dipole moment (EDM) bounds. We find that pair productions of first and second generation squarks serve as a viable probe of the CP violation sources in the gaugino sector of the theory even if experiments cannot determine chirality, flavor and electric charge of the squarks produced.Article Citation - WoS: 14Citation - Scopus: 15Cern Lep Indications for Two Light Higgs Bosons and the U(1)' Model(American Physical Society, 2006) Demir, Durmuş Ali; Solmaz, Levent; Solmaz, SaimeReanalyses of LEP data have shown preference to two light CP-even Higgs bosons. We discuss implications of such a Higgs boson spectrum for the minimal supersymmetric model extended by a standard model singlet chiral superfield and an additional Abelian gauge invariance [the U(1)′ model]. We, in particular, determine parameter regions that lead to two light CP-even Higgs bosons while satisfying existing bounds on the mass and mixings of the extra vector boson. In these parameter regions, the pseudoscalar Higgs is found to be nearly degenerate in mass with either the lightest or next-to-lightest Higgs boson. Certain parameters of the U(1)′ model such as the effective μ parameter are found to be significantly bounded by the LEP two light Higgs signal.Article Citation - WoS: 54Citation - Scopus: 55Persistence of Strong Electron Coupling To a Narrow Boson Spectrum in Overdoped Bi2sr2cacu2o8+î Tunneling Data(American Physical Society, 2006) Zasadzinski, John F.; Özyüzer, Lütfi; Coffey, L.; Gray, Kenneth E.; Hinks, David G.; Kendziora, Christopher A.A d-wave, Eliashberg analysis of break-junction and STM tunneling spectra on Bi2Sr2CaCu2O8+Î (Bi2212) reveals that the spectral dip feature is directly linked to strong electronic coupling to a narrow boson spectrum, evidenced by a large peak in I'2F(I). The tunneling dip feature remains robust in the overdoped regime of Bi2212 with bulk Tc values of 56Â Ka62Â K. This is contrary to recent optical conductivity measurements of the self-energy that suggest the narrow boson spectrum disappears in overdoped Bi2212 and therefore cannot be essential for the pairing mechanism. The discrepancy is resolved by considering the way each technique probes the electron self-energy, in particular, the unique sensitivity of tunneling to the off-diagonal or pairing part of the self-energy.Article Citation - WoS: 50Citation - Scopus: 53Nanoscale Oxide Growth on Al Single Crystals at Low Temperatures: Variable Charge Molecular Dynamics Simulations(American Physical Society, 2006) Hasnaoui, A.; Politano, O.; Salazar, J. M.; Aral, GürcanWe investigate the oxidation of aluminum low-index surfaces [(100), (110), and (111)] at low temperatures (300-600 K) and three different gas pressure values. We use molecular dynamics (MD) simulations with dynamic charge transfer between atoms where the interaction between atoms is described by the Es+ potential composed of the embedded atom method (EAM) potential and an electrostatic contribution. In the considered temperature range and under different gas pressure conditions, the growth kinetics follow a direct logarithmic law where the oxide thickness is limited to a value of ∼3 nm. The fitted curves allow us to determine the temperature and the pressure dependencies of the parameters involved in the growth law. During the adsorption stage, we observe a rotation of the oxygen pair as a precursor process to its dissociation. In most cases, the rotation aligns the molecule vertically to the Al surface. The separation distance after dissociation ranges from 3 to 9. Atomistic observations revealed that the oxide presents a dominant tetrahedral (Al O4) environment in the inner layer and mixed tetrahedral and octahedral (Al O6) environments in the outer oxide region when the oxide thickness reaches values beyond ∼2 nm.
- «
- 1 (current)
- 2
- 3
- »