Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
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Article Citation - WoS: 1Computational Investigation of Electronic, Vibrational, and Transport Properties of Silicon Phosphide Nanoribbons(American Physical Society, 2025) Sargin, G.Ö.; Jahangirzadeh Varjovi, M.J.; Ozbey, D.H.; Sevinçli, H.; Durgun, E.Two-dimensional (2D) silicon phosphide (SiP) has recently emerged as a promising semiconductor for electronic, optoelectronic, and thermoelectric applications due to its unique electronic and structural characteristics. One-dimensional (1D) nanoribbons (NRs) derived from 2D SiP offer a versatile and scalable platform for device miniaturization and performance enhancement in nanoelectronics. Motivated by their potential, we present a comprehensive first-principles investigation of the structural, electronic, dynamical, and electronic transport properties of SiP-NRs. Specifically, we focus on both bare and hydrogen-passivated armchair (A-NRs, HA-NRs) and zigzag (Z-NRs, HZ-NRs) configurations. Our results reveal that hydrogen passivation effectively suppresses edge reconstructions observed in bare SiP-NRs, thus dynamically stabilizing their structures. Analysis of electronic band structures demonstrates a clear width-dependent oscillatory behavior of the band gap in bare A-NRs, which diminishes significantly upon hydrogen termination. The width-scaled electronic conductance (G<inf>e</inf>ws) of HA-NRs exhibits a decreasing trend with increasing ribbon width, featuring distinct even-odd oscillations for n-type transport due to subband splitting effects. In contrast, HZ-NRs display notable deviations in p-type conductance from their 2D SiP counterpart, particularly at low temperatures (around 100 K), arising from residual localized edge states. However, with increasing width and temperature, transport behavior converges toward that of 2D SiP monolayers, indicating diminishing edge effects. Unlike their p-type counterparts, the n-type G<inf>e</inf> values of the largest HA-NRs and HZ-NRs increase with the square root of temperature, similar to the n-type conductance trend observed in 2D SiP. This behavior is attributed to the evolution of the electronic transmission function (τ(E)) from a steplike profile in narrow ribbons to an E1/2 dependence in wider ribbons, analogous to the 2D counterpart. These findings highlight the significant influence of width and edge termination on the transport characteristics of SiP-NRs and underline their potential as fundamental building blocks for high-performance nanoelectronic and thermoelectric quasi-1D devices. © 2025 authors. Published by the American Physical Society.Article Citation - WoS: 205Citation - Scopus: 159Search for Resonances and Quantum Black Holes Using Dijet Mass Spectra in Proton-Proton Collisions at S =8tev(American Physical Society, 2015) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; Hegeman, J.A search for resonances and quantum black holes is performed using the dijet mass spectra measured in proton-proton collisions at s=8TeV with the CMS detector at the LHC. The data set corresponds to an integrated luminosity of 19.7fb-1. In a search for narrow resonances that couple to quark-quark, quark-gluon, or gluon-gluon pairs, model-independent upper limits, at 95% confidence level, are obtained on the production cross section of resonances, with masses above 1.2 TeV. When interpreted in the context of specific models the limits exclude string resonances with masses below 5.0 TeV; excited quarks below 3.5 TeV; scalar diquarks below 4.7 TeV; W′ bosons below 1.9 TeV or between 2.0 and 2.2 TeV; Z′ bosons below 1.7 TeV; and Randall-Sundrum gravitons below 1.6 TeV. A separate search is conducted for narrow resonances that decay to final states including b quarks. The first exclusion limit is set for excited b quarks, with a lower mass limit between 1.2 and 1.6 TeV depending on their decay properties. Searches are also carried out for wide resonances, assuming for the first time width-to-mass ratios up to 30%, and for quantum black holes with a range of model parameters. The wide resonance search excludes axigluons and colorons with mass below 3.6 TeV, and color-octet scalars with mass below 2.5 TeV. Lower bounds between 5.0 and 6.3 TeV are set on the masses of quantum black holes. © 2015 CERN, for the CMS Collaboration.Article Citation - WoS: 1Citation - Scopus: 6Search for Supersymmetry With Photons in Pp Collisions at S =8tev(American Physical Society, 2015) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Calvo, E.Two searches for physics beyond the standard model in events containing photons are presented. The data sample used corresponds to an integrated luminosity of 19.7fb-1 of proton-proton collisions at s=8TeV, collected with the CMS experiment at the CERN LHC. The analyses pursue different inclusive search strategies. One analysis requires at least one photon, at least two jets, and a large amount of transverse momentum imbalance, while the other selects events with at least two photons and at least one jet, and uses the razor variables to search for signal events. The background expected from standard model processes is evaluated mainly from data. The results are interpreted in the context of general gauge-mediated supersymmetry, with the next-to-lightest supersymmetric particle either a bino- or wino-like neutralino, and within simplified model scenarios. Upper limits at the 95% confidence level are obtained for cross sections as functions of the masses of the intermediate supersymmetric particles. © 2015 CERN. © 2015 CERN, for the CMS Collaboration. Published by the American Physical Society under the terms of the "http://creativecommons.org/licenses/by/3.0/" Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Article Citation - WoS: 65Citation - Scopus: 62Search for the standard model Higgs boson produced through vector boson fusion and decaying to b¯b(American Physical Society, 2015) CMS Collaboration; Karapınar, GülerA first search is reported for a standard model Higgs boson (H) that is produced through vector boson fusion and decays to a bottom-quark pair. Two data samples, corresponding to integrated luminosities of 19.8fb-1 and 18.3fb-1 of proton-proton collisions at s=8TeV were selected for this channel at the CERN LHC. The observed significance in these data samples for a H→bb¯ signal at a mass of 125 GeV is 2.2 standard deviations, while the expected significance is 0.8 standard deviations. The fitted signal strength μ=σ/σSM=2.8-1.4+1.6. The combination of this result with other CMS searches for the Higgs boson decaying to a b-quark pair yields a signal strength of 1.0±0.4, corresponding to a signal significance of 2.6 standard deviations for a Higgs boson mass of 125 GeV. © 2015 CERN.Article Citation - WoS: 48Citation - Scopus: 69Limits on the Higgs Boson Lifetime and Width From Its Decay To Four Charged Leptons(American Physical Society, 2015) Khachatryan, V.; Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Soares, M.S.Constraints on the lifetime and width of the Higgs boson are obtained from H→ZZ→4ℓ events using data recorded by the CMS experiment during the LHC run 1 with an integrated luminosity of 5.1 and 19.7fb-1 at a center-of-mass energy of 7 and 8 TeV, respectively. The measurement of the Higgs boson lifetime is derived from its flight distance in the CMS detector with an upper bound of τH<1.9×10-13s at the 95% confidence level (C.L.), corresponding to a lower bound on the width of ΓH>3.5×10-9MeV. The measurement of the width is obtained from an off-shell production technique, generalized to include anomalous couplings of the Higgs boson to two electroweak bosons. From this measurement, a joint constraint is set on the Higgs boson width and a parameter fΛQ that expresses an anomalous coupling contribution as an on-shell cross-section fraction. The limit on the Higgs boson width is ΓH<46MeV with fΛQ unconstrained and ΓH<26MeV for fΛQ=0 at the 95% C.L. The constraint fΛQ<3.8×10-3 at the 95% C.L. is obtained for the expected standard model Higgs boson width. © 2015 CERN, for the CMS. Published by the American Physical Society.Article Citation - WoS: 149Citation - Scopus: 149Hexagonal Aln: Dimensional-Crossover Band-Gap Transition(American Physical Society, 2015) Bacaksız, Cihan; Şahin, Hasan; Özaydın, H. Duygu; Horzum, Şeyda; Senger, Ramazan Tugrul; Peeters, François M.Motivated by a recent experiment that reported the successful synthesis of hexagonal (h) AlN [Tsipas, Appl. Phys. Lett. 103, 251605 (2013)APPLAB0003-695110.1063/1.4851239], we investigate structural, electronic, and vibrational properties of bulk, bilayer, and monolayer structures of h-AlN by using first-principles calculations. We show that the hexagonal phase of the bulk h-AlN is a stable direct-band-gap semiconductor. The calculated phonon spectrum displays a rigid-layer shear mode at 274 cm-1 and an Eg mode at 703 cm-1, which are observable by Raman measurements. In addition, single-layer h-AlN is an indirect-band-gap semiconductor with a nonmagnetic ground state. For the bilayer structure, AA′-type stacking is found to be the most favorable one, and interlayer interaction is strong. While N-layered h-AlN is an indirect-band-gap semiconductor for N=1-9, we predict that thicker structures (N≥10) have a direct band gap at the Γ point. The number-of-layer-dependent band-gap transitions in h-AlN is interesting in that it is significantly different from the indirect-to-direct crossover obtained in the transition-metal dichalcogenides.Article Citation - WoS: 10Citation - Scopus: 10Spin-Spin Correlations of Magnetic Adatoms on Graphene(American Physical Society, 2015) Güçlü, Alev Devrim; Bulut, NejatWe study the interaction between two magnetic adatom impurities in graphene using the Anderson model. The two-impurity Anderson Hamiltonian is solved numerically by using the quantum Monte Carlo technique. We find that the interimpurity spin susceptibility is strongly enhanced at low temperatures, significantly diverging from the well-known Ruderman-Kittel-Kasuya-Yoshida result which decays as R-3.Article Citation - WoS: 35Citation - Scopus: 33Portlandite Crystal: Bulk, Bilayer, and Monolayer Structures(American Physical Society, 2015) Aierken, Y.; Şahin, Hasan; İyikanat, Fadıl; Horzum, Şeyda; Süslü, A.; Chen, B.; Senger, Ramazan Tugrul; Tongay, S.; Peeters, François M.Ca(OH)2 crystals, well known as portlandite, are grown in layered form, and we found that they can be exfoliated on different substrates. We performed first principles calculations to investigate the structural, electronic, vibrational, and mechanical properties of bulk, bilayer, and monolayer structures of this material. Different from other lamellar structures such as graphite and transition-metal dichalcogenides, intralayer bonding in Ca(OH)2 is mainly ionic, while the interlayer interaction remains a weak dispersion-type force. Unlike well-known transition-metal dichalcogenides that exhibit an indirect-to-direct band gap crossover when going from bulk to a single layer, Ca(OH)2 is a direct band gap semiconductor independent of the number layers. The in-plane Young's modulus and the in-plane shear modulus of monolayer Ca(OH)2 are predicted to be quite low while the in-plane Poisson ratio is larger in comparison to those in the monolayer of ionic crystal BN. We measured the Raman spectrum of bulk Ca(OH)2 and identified the high-frequency OH stretching mode A1g at 3620cm-1. In this study, bilayer and monolayer portlandite [Ca(OH)2] are predicted to be stable and their characteristics are analyzed in detail. Our results can guide further research on ultrathin hydroxites.Article Citation - WoS: 67Citation - Scopus: 66Tis3 Nanoribbons: Width-Independent Band Gap and Strain-Tunable Electronic Properties(American Physical Society, 2015) Kang, Jun; Şahin, Hasan; Özaydın, H. Duygu; Senger, Ramazan Tuğrul; Peeters, François M.The electronic properties, carrier mobility, and strain response of TiS3 nanoribbons (TiS3 NRs) are investigated by first-principles calculations. We found that the electronic properties of TiS3 NRs strongly depend on the edge type (a or b). All a-TiS3 NRs are metallic with a magnetic ground state, while b-TiS3 NRs are direct band gap semiconductors. Interestingly, the size of the band gap and the band edge position are almost independent of the ribbon width. This feature promises a constant band gap in a b-TiS3 NR with rough edges, where the ribbon width differs in different regions. The maximum carrier mobility of b-TiS3 NRs is calculated by using the deformation potential theory combined with the effective mass approximation and is found to be of the order 103cm2V-1s-1. The hole mobility of the b-TiS3 NRs is one order of magnitude lower, but it is enhanced compared to the monolayer case due to the reduction in hole effective mass. The band gap and the band edge position of b-TiS3 NRs are quite sensitive to applied strain. In addition we investigate the termination of ribbon edges by hydrogen atoms. Upon edge passivation, the metallic and magnetic features of a-TiS3 NRs remain unchanged, while the band gap of b-TiS3 NRs is increased significantly. The robust metallic and ferromagnetic nature of a-TiS3 NRs is an essential feature for spintronic device applications. The direct, width-independent, and strain-tunable band gap, as well as the high carrier mobility, of b-TiS3 NRs is of potential importance in many fields of nanoelectronics, such as field-effect devices, optoelectronic applications, and strain sensors.Article Citation - WoS: 45Citation - Scopus: 43Tuning the Magnetic Anisotropy in Single-Layer Crystal Structures(American Physical Society, 2015) Torun, Engin; Şahin, Hasan; Bacaksız, Cihan; Senger, Ramazan Tugrul; Peeters, François M.The effect of an applied electric field and the effect of charging are investigated on the magnetic anisotropy (MA) of various stable two-dimensional (2D) crystals such as graphene, FeCl2, graphone, fluorographene, and MoTe2 using first-principles calculations. We found that the magnetocrystalline anisotropy energy of Co-on-graphene and Os-doped-MoTe2 systems change linearly with electric field, opening the possibility of electric field tuning MA of these compounds. In addition, charging can rotate the easy-axis direction of Co-on-graphene and Os-doped-MoTe2 systems from the out-of-plane (in-plane) to in-plane (out-of-plane) direction. The tunable MA of the studied materials is crucial for nanoscale electronic technologies such as data storage and spintronics devices. Our results show that controlling the MA of the mentioned 2D crystal structures can be realized in various ways, and this can lead to the emergence of a wide range of potential applications where the tuning and switching of magnetic functionalities are important.