Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 31 for “"superconducting gap"”.
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Probing the Superconducting Gap of Lead With Ballistic Phonons
… we extract consistent values of both the superconducting energy gap parameter and the superconducting phonon absorption coefficient for all phonon-imaging data. Measured values of the energy gap (Delta = 1.32+/-0.07 meV)are consistent with accepted values from tunneling measurements. …
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Point-contact Andreev reflection studies on superconductors
… used to investigate the density of states and superconducting gap structure of several novel superconducting systems. Theoretical and experimental background is given with an emphasis on PCARS as applied to various unconventional superconductors, such as NbSe$_2$, the borocarbide family …
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Temperature dependence of impurity resonances in cuprate superconductors
In conventional superconductors the superconducting gap in the electronic excitation spectrum prevents scattering of low energy electrons. In high temperature superconductors (HTS) an additional gap, the pseudogap, develops well above the superconducting transition temperature Tc. The identity of …
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Planar tunneling spectroscopy of thin-film Nb, Nb/normal metal and Nb/semiconductor structures
… been investigated. A thickness dependence of the superconducting critical temperature Tc and the superconducting gap parameter Δ have been observed for thin film superconductor/normal metal structures. Although many studies exist, the underlying mechanism is not fully understood. The …
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Nuclear Magnetic Resonance Studies of the High-Temperature Superconductors in the Normal and Superconducting States
… the antiferromagnetic correlation length. In the superconducting mixed state of YBa2Cu3O7-delta we find evidence for an unconventional field dependence of the density of states at the Fermi level. This field dependence agrees with a recent prediction by Volovik that a superconductor with nodal …
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Light scattering studies of heavy fermion and high Tc superconductors
… at high energies due to the direct excitation of superconducting quasiparticle pairs above the gap. The observed anisotropy in the Raman matrix elements associated with these superconducting gap excitations lV presents strong evidence for substantial gap anisotropy in YBa2Cu301-B· However, our …
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Low Energy Electronic Raman Scattering in Cuprate High Temperature Superconductors
… in overdoped Tl-2201 implies that the superconducting gap opens very rapidly below the critical temperature. The measured peak intensity as a function of temperature, however, shows an anomalous behavior. A magnetic field is observed to affect Raman spectra in way similar to the way …
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Communal pairing in Fermi gases with attractive interactions
… wave theory. We propose a further extension of a superconducting state, dubbed a communal pairing state, whose underlying components are superpositions of Cooper pairs that share minority-spin fermions. This state includes correlations between all available fermions on both Fermi surfaces and is …
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The magnetic properties of the cuprate superconductors
… cuprate superconductors in both the normal and superconducting states. The magnetic properties are studied by making comparison to the results of nuclear magnetic resonance experiments. The author gives a simplification of the method used to calculate the nuclear magnetic resonance spin-echo …
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Engineering superconductivity in ballistic semiconductor nanowires
… a superconductor and nanowire leads to a “soft superconducting gap” that prevents the topological nature of Majorana states to be tested. Therefore, pristine semiconductor-superconductor interfaces must be developed. Second, a lack of ballistic 1D behavior can induce quantum-localized bound …
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Probing the superconducting order parameter of Iron-based superconductors through the Josephson effect
… Josephson effect to probe the symmetry of the superconducting order parameter of Co-doped Ba(FeAs)2 crystals (Ba122). This measurements were carried out to test the validity of the s± model, which predicts the pairing in the multiband Ba122 compounds being mediated by the exchange of spin …
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Angle-resolved photoemission and first-principles studies of topological semimetals and heterostructures
… to a topological state typically involves a gap reversal caused by a strong SOC. By theoretically adjusting the SOC strength, we can observe the changes in the electronic band structure and make conclusions about the topological phase of the system. Using this method, we constructed a …
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Visualizing Cooper Pair Formation on the Atomic Scale in High Temperature Superconductors
… scale. The magnitude of the low-temperature superconducting gap measured in Bi2Sr2CaCu 2O8+delta shows a large nanoscale spatial variation. These superconducting gaps evolve smoothly with temperature and close locally over a range of temperatures above the superconducting transition …
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Phenomenological phase-fluctuation model for the underdoped cuprates
… phase-fluctuation model for the pseudogap regime of the underdoped cuprates was discussed. The key idea of the phase-fluctuation scenario in the high-T_c superconductors is the notion that the pseudogap observed in a wide variety of experiments arises from phase fluctuations of the …
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Spectroscopic studies of high-temperature superconductors on planar tunnel junction devices and nanofabricated point contact junctions
… show the clear density of states signature of superconducting Nb. The junction resistance times area product increases exponentially with barrier thickness, further supporting the high quality of the junctions, in which single-step elastic tunneling predominates. The second new approach is the …
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Investigating the relationship between the superconducting and pseudogap states of the high-temperature superconductor Bi-2201 using scanning tunneling microscopy
… the nature of the relationship between the superconducting and pseudogap states of high-temperature superconductors. Although there exist a large number of theories regarding their relationship, the theories fall into one of two broad classes. The first class views the superconducting state …
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The role of inter-plane interaction in the electronic structure of high Tc cuprates
… structure of the modulation-free Pb-doped Bi2212 superconducting cuprates with respect to interlayer coupling done by using the angle-resolved photoemission spectroscopy (ARPES), which is a leading technique in the experimental investigation of the single particle excitations in solids. The …
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Majorana qubits in non-Abelian topological superconductors
… topological degeneracy, thermal excitations and superconducting fluctuations which are not treated in the usual BCS mean-field theory. We calculate the tunneling splitting between non-Abelian vortices in both chiral p+ip superconductors and the superconductor/topological insulator het- …
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Variable Temperature Scanning Tunneling Microscopy Study of a High Temperature Superconductor Bi2Sr2CaCu2O8+d
… of local electronic density of states below the superconducting gap energy. In this thesis, I also present our observations and analysis of the few differences between our data at 40 K and preexisting low-temperature results. The key results at 100 K are our observation of local electronic …
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Light scattering studies of phonon anomalies and superconductivity in A15 compounds
… the superconduct1ng state close in energy to the superconducting gap 28. These are attributed to direct electronic Raman scattering by pairs of superconducting quasiparticles. A theory is presented which fits the data well and provides evidence for anisotropy of the gap (-20 %in Nb3Sn) and of the …
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