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Rao SS, Jammalamadaka SN, Stesmans A, Moshchalkov VV, van Tol J, Kosynkin DV, Higginbotham-Duque A, Tour JM. Ferromagnetism in graphene nanoribbons: split versus oxidative unzipped ribbons. NANO LETTERS 2012; 12:1210-1217. [PMID: 22320177 DOI: 10.1021/nl203512c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Two types of graphene nanoribbons: (a) potassium-split graphene nanoribbons (GNRs), and (b) oxidative unzipped and chemically converted graphene nanoribbons (CCGNRs) were investigated for their magnetic properties using the combination of static magnetization and electron spin resonance measurements. The two types of ribbons possess remarkably different magnetic properties. While a low-temperature ferromagnet-like feature is observed in both types of ribbons, such room-temperature feature persists only in potassium-split ribbons. The GNRs show negative exchange bias, but the CCGNRs exhibit a "positive exchange bias". Electron spin resonance measurements suggest that the carbon-related defects may be responsible for the observed magnetic behavior in both types of ribbons. Furthermore, information on the proton hyperfine coupling strength has been obtained from hyperfine sublevel correlation experiments performed on the GNRs. Electron spin resonance finds no evidence for the presence of potassium (cluster) related signals, pointing to the intrinsic magnetic nature of the ribbons. Our combined experimental results may indicate the coexistence of ferromagnetic clusters with antiferromagnetic regions leading to disordered magnetic phase. We discuss the possible origin of the observed contrast in the magnetic behaviors of the two types of ribbons studied.
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Valev VK, Denkova D, Zheng X, Kuznetsov AI, Reinhardt C, Chichkov BN, Tsutsumanova G, Osley EJ, Petkov V, De Clercq B, Silhanek AV, Jeyaram Y, Volskiy V, Warburton PA, Vandenbosch GAE, Russev S, Aktsipetrov OA, Ameloot M, Moshchalkov VV, Verbiest T. Plasmon-enhanced sub-wavelength laser ablation: plasmonic nanojets. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2012; 24:OP29-35. [PMID: 22228434 DOI: 10.1002/adma.201103807] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 11/24/2011] [Indexed: 05/12/2023]
Abstract
In response to the incident light's electric field, the electron density oscillates in the plasmonic hotspots producing an electric current. Associated Ohmic losses raise the temperature of the material within the plasmonic hotspot above the melting point. A nanojet and nanosphere ejection can then be observed precisely from the plasmonic hotspots.
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Valev VK, Clercq BD, Zheng X, Denkova D, Osley EJ, Vandendriessche S, Silhanek AV, Volskiy V, Warburton PA, Vandenbosch GAE, Ameloot M, Moshchalkov VV, Verbiest T. The role of chiral local field enhancements below the resolution limit of Second Harmonic Generation microscopy. OPTICS EXPRESS 2012; 20:256-264. [PMID: 22274348 DOI: 10.1364/oe.20.000256] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
While it has been demonstrated that, above its resolution limit, Second Harmonic Generation (SHG) microscopy can map chiral local field enhancements, below that limit, structural defects were found to play a major role. Here we show that, even below the resolution limit, the contributions from chiral local field enhancements to the SHG signal can dominate over those by structural defects. We report highly homogeneous SHG micrographs of star-shaped gold nanostructures, where the SHG circular dichroism effect is clearly visible from virtually every single nanostructure. Most likely, size and geometry determine the dominant contributions to the SHG signal in nanostructured systems.
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Novitchi G, Pilet G, Ungur L, Moshchalkov VV, Wernsdorfer W, Chibotaru LF, Luneau D, Powell AK. Heterometallic CuII/DyIII 1D chiral polymers: chirogenesis and exchange coupling of toroidal moments in trinuclear Dy3 single molecule magnets. Chem Sci 2012. [DOI: 10.1039/c2sc00728b] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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55
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Shestakov MV, Baranov AN, Tikhomirov VK, Zubavichus YV, Kuznetsov AS, Veligzhanin AA, Kharin AY, Rösslhuber R, Timoshenko VY, Moshchalkov VV. Energy-transfer luminescence of a zinc oxide/ytterbium oxide nanocomposite. RSC Adv 2012. [DOI: 10.1039/c2ra20755a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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56
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Valev VK, Silhanek AV, De Clercq B, Gillijns W, Jeyaram Y, Zheng X, Volskiy V, Aktsipetrov OA, Vandenbosch GAE, Ameloot M, Moshchalkov VV, Verbiest T. U-shaped switches for optical information processing at the nanoscale. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2011; 7:2573-6. [PMID: 21793204 DOI: 10.1002/smll.201100752] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Indexed: 05/08/2023]
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57
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Mamonov EA, Murzina TV, Kolmychek IA, Maydykovsky AI, Valev VK, Silhanek AV, Ponizovskaya E, Bratkovsky A, Verbiest T, Moshchalkov VV, Aktsipetrov OA. Coherent and incoherent second harmonic generation in planar G-shaped nanostructures. OPTICS LETTERS 2011; 36:3681-3683. [PMID: 21931431 DOI: 10.1364/ol.36.003681] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Azimuthal anisotropy of Stokes parameters of the second harmonic generation (SHG) generated and observed in reflection from a periodic planar area of G-shaped gold nanostructures is studied. A strong anisotropy of both coherent and incoherent SHG components is observed. Finite-difference time-domain calculations prove that the observed effects are due to the anisotropic enhancement of the fundamental radiation within the G-shaped structures.
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58
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Shestakov MV, Tikhomirov VK, Kirilenko D, Kuznetsov AS, Chibotaru LF, Baranov AN, Van Tendeloo G, Moshchalkov VV. Quantum cutting in Li (770 nm) and Yb (1000 nm) co-dopant emission bands by energy transfer from the ZnO nano-crystalline host. OPTICS EXPRESS 2011; 19:15955-15964. [PMID: 21934959 DOI: 10.1364/oe.19.015955] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Li-Yb co-doped nano-crystalline ZnO has been synthesized by a method of thermal growth from the salt mixtures. X-ray diffraction, transmission electron microscopy, atomic absorption spectroscopy and optical spectroscopy confirm the doping and indicate that the dopants may form Li-Li and Yb(3+)-Li based nanoclusters. When pumped into the conduction and exciton absorption bands of ZnO between 250 to 425 nm, broad emission bands of about 100 nm half-height-width are excited around 770 and 1000 nm, due to Li and Yb dopants, respectively. These emission bands are activated by energy transfer from the ZnO host mostly by quantum cutting processes, which generate pairs of quanta in Li (770 nm) and Yb (1000 nm) emission bands, respectively, out of one quantum absorbed by the ZnO host. These quantum cutting phenomena have great potential for application in the down-conversion layers coupled to the Si solar cells.
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Cho JH, Keung MD, Verellen N, Lagae L, Moshchalkov VV, Van Dorpe P, Gracias DH. Nanoscale origami for 3D optics. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2011; 7:1943-8. [PMID: 21671431 DOI: 10.1002/smll.201100568] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Indexed: 05/25/2023]
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60
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Verellen N, Van Dorpe P, Vercruysse D, Vandenbosch GAE, Moshchalkov VV. Dark and bright localized surface plasmons in nanocrosses. OPTICS EXPRESS 2011; 19:11034-11051. [PMID: 21716332 DOI: 10.1364/oe.19.011034] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A metallic nanocross geometry sustaining broad dipole and sharp higher order localized surface plasmon resonances is investigated. Spectral tunability is achieved by changing the cross arm length and the angle between the arms. The degree of rotational symmetry of the nanocross is varied by adding extra arms, changing the arm angle and shifting the arm intersection point. The particle's symmetry is shown to have a crucial influence on the plasmon coupling to incident radiation. Pronounced dipole, quadrupole, octupole and Fano resonances are observed in individual cross structures. Furthermore, the nanocross geometry proves to be a useful building block for coherently coupled plasmonic dimers and trimers where the reduced symmetry results in hybridized subradiant and superradiant modes and multiple Fano interferences. Finite difference time domain calculations of absorption and scattering cross-sections as well as charge density profiles are used to reveal the nature of the different plasmon modes. Experimental spectra for the discussed geometries support the calculations.
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61
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Valev VK, Silhanek AV, Jeyaram Y, Denkova D, De Clercq B, Petkov V, Zheng X, Volskiy V, Gillijns W, Vandenbosch GAE, Aktsipetrov OA, Ameloot M, Moshchalkov VV, Verbiest T. Hotspot decorations map plasmonic patterns with the resolution of scanning probe techniques. PHYSICAL REVIEW LETTERS 2011; 106:226803. [PMID: 21702624 DOI: 10.1103/physrevlett.106.226803] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 03/23/2011] [Indexed: 05/31/2023]
Abstract
In high definition mapping of the plasmonic patterns on the surfaces of nanostructures, the diffraction limit of light remains an important obstacle. Here we demonstrate that this diffraction limit can be completely circumvented. We show that upon illuminating nanostructures made of nickel and palladium, the resulting surface-plasmon pattern is imprinted on the structures themselves; the hotspots (regions of local field enhancement) are decorated with overgrowths, allowing for their subsequent imaging with scanning-probe techniques. The resulting resolution of plasmon pattern imaging is correspondingly improved.
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62
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Van de Vondel J, Gladilin VN, Silhanek AV, Gillijns W, Tempere J, Devreese JT, Moshchalkov VV. Vortex core deformation and stepper-motor ratchet behavior in a superconducting aluminum film containing an array of holes. PHYSICAL REVIEW LETTERS 2011; 106:137003. [PMID: 21517415 DOI: 10.1103/physrevlett.106.137003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Indexed: 05/30/2023]
Abstract
We investigated experimentally the frequency dependence of a superconducting vortex ratchet effect by means of electrical transport measurements and modeled it theoretically using the time-dependent Ginzburg-Landau formalism. We demonstrate that the high frequency vortex behavior can be described as a discrete motion of a particle in a periodic potential, i.e., the so-called stepper-motor behavior. Strikingly, in the more conventional low frequency response a transition takes place from an Abrikosov vortex rectifier to a phase slip line rectifier. This transition is characterized by a strong increase in the rectified voltage and the appearance of a pronounced hysteretic behavior.
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63
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Verellen N, Van Dorpe P, Huang C, Lodewijks K, Vandenbosch GAE, Lagae L, Moshchalkov VV. Plasmon line shaping using nanocrosses for high sensitivity localized surface plasmon resonance sensing. NANO LETTERS 2011; 11:391-7. [PMID: 21265553 DOI: 10.1021/nl102991v] [Citation(s) in RCA: 170] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The detection of small changes in the wavelength position of localized surface plasmon resonances in metal nanostructures has been used successfully in applications such as label-free detection of biomarkers. Practical implementations, however, often suffer from the large spectral width of the plasmon resonances induced by large radiative damping in the metal nanocavities. By means of a tailored design and using a reproducible nanofabrication process, high quality planar gold plasmonic nanocavities are fabricated with strongly reduced radiative damping. Moreover, additional substrate etching results in a large enhancement of the sensing volume and a subsequent increase of the sensitivity. Coherent coupling of bright and dark plasmon modes in a nanocross and nanobar is used to generate high quality factor subradiant Fano resonances. Experimental sensitivities for these modes exceeding 1000 nm/RIU with a Figure of Merit reaching 5 are demonstrated in microfluidic ensemble spectroscopy.
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64
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Valev VK, Silhanek AV, Gillijns W, Jeyaram Y, Paddubrouskaya H, Volodin A, Biris CG, Panoiu NC, De Clercq B, Ameloot M, Aktsipetrov OA, Moshchalkov VV, Verbiest T. Plasmons reveal the direction of magnetization in nickel nanostructures. ACS NANO 2011; 5:91-6. [PMID: 21141981 DOI: 10.1021/nn102852b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
We have applied the surface-sensitive nonlinear optical technique of magnetization-induced second harmonic generation (MSHG) to plasmonic, magnetic nanostructures made of Ni. We show that surface plasmon contributions to the MSHG signal can reveal the direction of the magnetization. Both the plasmonic and the magnetic nonlinear optical responses can be tuned; our results indicate novel ways to combine nanophotonics, nanoelectronics, and nanomagnetics and suggest the possibility for large magneto-chiral effects in metamaterials.
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65
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Tikhomirov VK, Rodríguez VD, Kuznetsov A, Kirilenko D, Van Tendeloo G, Moshchalkov VV. Preparation and luminescence of bulk oxyfluoride glasses doped with Ag nanoclusters. OPTICS EXPRESS 2010; 18:22032-22040. [PMID: 20941104 DOI: 10.1364/oe.18.022032] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Bulk oxyfluoride glasses doped with Ag nanoclusters have been prepared using the melt quenching technique. When pumped in the absorption band of Ag nanoclusters between 300 to 500 nm, these glasses emit a very broad luminescence band covering all the visible range with a weak tail extending into the near infrared. The maximum of the luminescence band and its color shifts to the blue with a shortening of the excitation wavelength and an increasing ratio of oxide to fluoride components, resulting in white color luminescence at a particular ratio of oxide to fluoride; with a quantum yield above 20%.
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66
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Tikhomirov VK, Adamo G, Nikolaenko AE, Rodriguez VD, Gredin P, Mortier M, Zheludev NI, Moshchalkov VV. Cathodo- and photoluminescence in Yb(3+)-Er(3+) co-doped PbF(2) nanoparticles. OPTICS EXPRESS 2010; 18:8836-8846. [PMID: 20588728 DOI: 10.1364/oe.18.008836] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We have prepared and studied the PbF(2):(Yb(3+),Er(3+)) co-doped nanoparticles, with chemical formula (Yb-Er)(x)Pb(1-x)F(2+x), where x = 0.29, Yb(3+)/Er(3+) = 6, and estimated the energy efficiency for their cathodoluminescence, mostly of Yb(3+), and up-conversion photoluminescence of Er(3+) to reach more than 0.5% and 20%, respectively, which may be the highest to date for rare-earth doped nanoparticles. Electron beam induced temperature rise in the nanoparticles has been estimated by measuring the ratio of green emission bands of Er(3+). These high efficiencies are due to high doping level of nanoparticles and due to low phonon energy of the PbF(2) host.
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67
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Valev VK, Silhanek AV, Smisdom N, De Clercq B, Gillijns W, Aktsipetrov OA, Ameloot M, Moshchalkov VV, Verbiest T. Linearly polarized second harmonic generation microscopy reveals chirality. OPTICS EXPRESS 2010; 18:8286-8293. [PMID: 20588674 DOI: 10.1364/oe.18.008286] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
In optics, chirality is typically associated with circularly polarized light. Here we present a novel way to detect the handedness of chiral materials with linearly polarized light. We performed Second Harmonic Generation (SHG) microscopy on G-shaped planar chiral nanostructures made of gold. The SHG response originates in distinctive hotspots, whose arrangement is dependent of the handedness. These results uncover new directions for studying chirality in artificial materials.
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68
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Valev VK, Silhanek AV, Verellen N, Gillijns W, Van Dorpe P, Aktsipetrov OA, Vandenbosch GAE, Moshchalkov VV, Verbiest T. Asymmetric optical second-harmonic generation from chiral G-shaped gold nanostructures. PHYSICAL REVIEW LETTERS 2010; 104:127401. [PMID: 20366565 DOI: 10.1103/physrevlett.104.127401] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Indexed: 05/29/2023]
Abstract
We present a new electromagnetic phenomenon-the asymmetric second-harmonic generation from planar chiral structures. The effect consists in distinguishing the handedness of a chiral material by rotating the sample in an experiment involving solely linearly polarized light. This phenomenon originates in the surface plasmon resonance of chiral gold nanostructures, where homodyne interference of anisotropic and chiral electric and/or magnetic multipoles appears to play an important role.
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69
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Sonnefraud Y, Verellen N, Sobhani H, Vandenbosch GAE, Moshchalkov VV, Van Dorpe P, Nordlander P, Maier SA. Experimental realization of subradiant, superradiant, and fano resonances in ring/disk plasmonic nanocavities. ACS NANO 2010; 4:1664-70. [PMID: 20155967 DOI: 10.1021/nn901580r] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Subradiant and superradiant plasmon modes in concentric ring/disk nanocavities are experimentally observed. The subradiance is obtained through an overall reduction of the total dipole moment of the hybridized mode due to antisymmetric coupling of the dipole moments of the parent plasmons. Multiple Fano resonances appear within the superradiant continuum when structural symmetry is broken via a nanometric displacement of the disk, due to coupling with higher order ring modes. Both subradiant modes and Fano resonances exhibit substantial reductions in line width compared to the parent plasmon resonances, opening up possibilities in optical and near IR sensing via plasmon line shape design.
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70
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Silhanek AV, Milosević MV, Kramer RBG, Berdiyorov GR, Van de Vondel J, Luccas RF, Puig T, Peeters FM, Moshchalkov VV. Formation of stripelike flux patterns obtained by freezing kinematic vortices in a superconducting Pb film. PHYSICAL REVIEW LETTERS 2010; 104:017001. [PMID: 20366384 DOI: 10.1103/physrevlett.104.017001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Indexed: 05/29/2023]
Abstract
We demonstrate experimentally and theoretically that the dissipative state of superconducting samples with a periodic array of holes at high current densities consists of flux rivers resulting from a short-range attractive interaction between vortices. This dynamically induced vortex-vortex attraction results from the migration of quasiparticles out of the vortex core (kinematic vortices). We have directly visualized the formation of vortex chains by scanning Hall probe microscopy after freezing the dynamic state by a field cooling procedure at a constant bias current. Similar experiments carried out in a sample without holes show no hint of flux river formation. We shed light on this nonequilibrium phenomena modeled by time-dependent Ginzburg-Landau simulations.
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71
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Hallet X, Mátéfi-Tempfli M, Michotte S, Piraux L, Vanacken J, Moshchalkov VV, Mátéfi-Tempfli S. Quasi-hexagonal vortex-pinning lattice using anodized aluminum oxide nanotemplates. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2009; 5:2413-2416. [PMID: 19634185 DOI: 10.1002/smll.200900400] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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72
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Valev VK, Smisdom N, Silhanek AV, De Clercq B, Gillijns W, Ameloot M, Moshchalkov VV, Verbiest T. Plasmonic ratchet wheels: switching circular dichroism by arranging chiral nanostructures. NANO LETTERS 2009; 9:3945-8. [PMID: 19863052 DOI: 10.1021/nl9021623] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We demonstrate circular dichroism (CD) in the second harmonic generation (SHG) signal from chiral assemblies of G-shaped nanostructures made of gold. The arrangement of the G shapes is crucial since upon reordering them the SHG-CD effect disappears. Microscopy reveals SHG "hotspots" assemblies, which originate in enantiomerically sensitive plasmon modes, having the novel property of exhibiting a chiral geometry themselves in relation with the handedness of the material. These results open new frontiers in studying chirality.
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73
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Kramer RBG, Silhanek AV, Van de Vondel J, Raes B, Moshchalkov VV. Symmetry-induced giant vortex state in a superconducting Pb film with a fivefold Penrose array of magnetic pinning centers. PHYSICAL REVIEW LETTERS 2009; 103:067007. [PMID: 19792602 DOI: 10.1103/physrevlett.103.067007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Indexed: 05/28/2023]
Abstract
A direct visualization of the flux distribution in a Pb film covering a fivefold Penrose array of Co dots is obtained by mapping the local field distribution with a scanning Hall probe microscope. We demonstrate that stable vortex configurations can be found for fields H approximately 0.8H_{1}, H_{1}, and 1.6H_{1}, where H_{1} corresponds to one flux quantum per pinning site. The vortex pattern at 0.8H_{1} corresponds to one vacancy in one of the vertices of the thin tiles, whereas at 1.6H_{1} the vortex structure can be associated with one interstitial vortex inside each thick tile. Strikingly, for H = 1.6H_{1}, interstitial and pinned vortices arrange themselves in ringlike structures ("vortex corrals") which favor the formation of a giant vortex state at their center.
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74
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Tikhomirov VK, Driesen K, Rodriguez VD, Gredin P, Mortier M, Moshchalkov VV. Optical nanoheater based on the Yb3+-Er3+ co-doped nanoparticles. OPTICS EXPRESS 2009; 17:11794-11798. [PMID: 19582094 DOI: 10.1364/oe.17.011794] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Yb(3+)-Er(3+) co-doped fluoride nanoparticles have been prepared. When pumped by 975 nm laser diode into absorption band of Yb(3+), the laser-induced temperature rise up to 800 degrees C has been detected in the nanoparticles by measuring the ratio of the intensities of the thermalised up-conversion luminescence bands (2)H(11/2)-->(4)I(15/2) and (4)S(3/2)-->(4)I(15/2) of Er(3+). These results show that a controlled optical heating of the nanoparticles and their surrounding nano-volumes can be realised, while the location and temperature rise of the nanoparticles and heated nano-volumes can be detected distantly by means of luminescence.
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75
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Vervaeke K, Simoen E, Borghs G, Moshchalkov VV. Size dependence of microscopic Hall sensor detection limits. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2009; 80:074701. [PMID: 19655970 DOI: 10.1063/1.3160105] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In this paper the magnetic field detection limits of microscopic Hall sensors are investigated as a function of their lateral size. Hall sensors fabricated from GaAs/AlGaAs heterostructures and silicon are experimentally investigated at different temperatures using Hall effect and noise spectrum measurements. At room temperature a clear size dependence of the detection limit is observed, whereas at low temperatures this dependence is found to disappear. The results are explained using the theory of noise in semiconductors.
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