Showing papers on "High-temperature superconductivity published in 2002"
TL;DR: A blue shift of the ab-plane plasma frequency when the material became superconducting, indicating that the spectral weight was transferred to the infrared range, is observed, in agreement with models in which superconductivity is accompanied by an increased charge carrier spectral weight.
Abstract: Optical data are reported on a spectral weight transfer over a broad frequency range of Bi2Sr2CaCu2O8+δ, when this material became superconducting. Using spectroscopic ellipsometry, we observed the removal of a small amount of spectral weight in a broad frequency band from 104 cm−1 to at least 2 × 104 cm−1, due to the onset of superconductivity. We observed a blue shift of the ab-plane plasma frequency when the material became superconducting, indicating that the spectral weight was transferred to the infrared range. Our observations are in agreement with models in which superconductivity is accompanied by an increased charge carrier spectral weight. The measured spectral weight transfer is large enough to account for the condensation energy in these compounds.
231 citations
TL;DR: In this article, it was shown that the resonant mode is present in Tl2Ba2CuO6+δ, a single-layer compound with a superconducting transition temperature of ∼90 kelvin, demonstrating that it is a generic feature of the copper oxide superconductors.
Abstract: An unusual spin excitation mode observed by neutron scattering has inspired numerous theoretical studies of the interplay between charged quasiparticles and collective spin excitations in the copper oxide high-temperature superconductors. The mode has, thus far, only been observed in materials with crystal structures consisting of copper oxide bilayers, and it is absent in the single-layer compound La2−xSrxCuO4+δ. Neutron-scattering data now show that the mode is present in Tl2Ba2CuO6+δ, a single-layer compound with a superconducting transition temperature of ∼90 kelvin, demonstrating that it is a generic feature of the copper oxide superconductors, independent of the layer sequence. This restricts the theoretical models for the origin of the resonant mode and its role in the mechanism of high-temperature superconductivity.
166 citations
01 Dec 2002
TL;DR: In this article, the fundamental properties of superconductivity and superconducting materials are discussed, including the critical currents of type II superconductors and their application in high current applications.
Abstract: VOLUME I: SUPERCONDUCTIVITY, MATERIALS AND PROCESSES Fundamentals of Superconductivity Introduction to superconductivity and superconducting materials Characteristic properties Elementary theory Critical currents of type II superconductors Processing Introduction to processing methods Bulk materials Wires and tapes Thick and thin films Superconductor contacts High Temperature Superconductors YBCO BSCCO TIBCCO Mercury superconductors Magnesium diboride VOLUME II: CHARACTERIZATION, APPLICATION AND CRYOGENICS Characterization Techniques Structure/microstructure Measurement and interpretation of electromagnetic properties Measurement of physical properties Applications High current applications Trapped flux devices High frequency devices Josephson junction devices Other devices Introduction to Refrigeration Methods Emerging Materials Chevrel phases Unconventional superconductivity in heavy fermion and ruthenate superconductors Organic superconductors Fullerene superconductors Future high Tc superconductors Appendices Manufacturer and supplier directory Hazards: environment and safety Teach yourself phase diagrams
99 citations
TL;DR: In this paper, the magnetic pattern of YBa(2)Cu(3)O(6.35) superconductors was analyzed and the role of striped phases was clarified.
Abstract: Neutron scattering has been used to measure the charge and spin structure in the highly underdoped superconductor YBa(2)Cu(3)O(6.35). Incommensurate static charge ordering is found that remains at high temperatures. The magnetic pattern is complex with a resonance and incommensurate structure observed at low temperatures. The results clarify the role of striped phases in YBa(2)Cu(3)O(6+x) superconductors.
99 citations
TL;DR: In this paper, a generic Frohlich-Coulomb model of oxides, which also includes infinite on-site (Hubbard) repulsion, was introduced, and a simple analytical method of solving the multi-polaron problem in complex lattice structures was described.
Abstract: We introduce a generic Frohlich-Coulomb model of the oxides, which also includes infinite on-site (Hubbard) repulsion, and describe a simple analytical method of solving the multi-polaron problem in complex lattice structures. Two particular lattices, a zigzag ladder and a perovskite layer, are studied. We find that, depending on the relative strength of the Frohlich and Coulomb interactions, these systems are either polaronic Fermi (or Luttinger) liquids, bipolaronic superconductors, or charge-segregated insulators. In the superconducting phase the carriers are superlight mobile bipolarons. The model describes key features of the cuprates such as their Tc-values, the isotope effects, the normal-state diamagnetism, the pseudogap, and spectral functions measured in tunnelling and photoemission. We argue that a low Fermi energy and strong coupling of carriers with high-frequency phonons is the cause of high critical temperatures in novel superconductors.
82 citations
Abstract: A need exists for low-cost coated-conductor fabrication methods for applications in magnet and electric-power technologies We demonstrate high-critical current density (Jc) YBa2Cu3O7−δ (YBCO) films grown on Nb-doped SrTiO3 (Nb:STO) buffered Ni(100) tapes All buffer and superconductor layers are deposited using solution chemistry A 50 nm thick Nb:STO seed layer on Ni(100) acts as a template for the growth of subsequent thicker layers of Nb:STO Nb doping improves the electrical conductivity and oxygen diffusion barrier properties of STO YBCO grows heteroepitaxially directly on this buffer layer, resulting in a transport Jc(77 K)=13 MA/cm2
81 citations
TL;DR: It is shown that its small intensity and weak coupling to electron-hole pairs (as deduced from the measured lifetime) disqualifies the resonant mode from either proposed role.
Abstract: In certain cuprates, a spin-1 resonance mode is prominent in the magnetic structure measured by neutron scattering. It has been proposed that this mode is responsible for significant features seen in other spectroscopies, such as photoemission and optical absorption, which are sensitive to the charge dynamics, and even that this mode is the boson responsible for "mediating" the superconducting pairing. We show that its small (measured) intensity and weak coupling to electron-hole pairs (as deduced from the measured lifetime) disqualifies the resonant mode from either proposed role.
77 citations
TL;DR: In this paper, the depression of the superconducting critical temperature of ultrathin YBa2Cu3O7 (YBCO) layers, when their thickness is reduced in the presence of La0.7Ca0.3MnO3 (LCMO) magnetic layers in [LCMO (15 unit cells)/Y-BCO (N unit cells)] superlattices, was investigated.
Abstract: We report on the depression of the superconducting critical temperature of ultrathin YBa2Cu3O7 (YBCO) layers, when their thickness is reduced in the presence of La0.7Ca0.3MnO3 (LCMO) magnetic layers in [LCMO (15 unit cells)/YBCO (N unit cells)] superlattices. The thickness of the manganite layer is kept at 15 unit cells and the YBCO thickness is varied between N=12 and N=1 unit cells. The structural analysis, using x-ray diffraction and electron microscopy, shows sharp interfaces with little structural disorder. While a critical temperature, TC=85 K, is found for 12 YBCO unit cells, superconductivity is completely suppressed for YBCO layer thickness below 3 unit cells. The possible interaction between superconductivity and magnetism is investigated.
76 citations
TL;DR: In this article, a generic Froehlich-Coulomb model of oxides, which also includes infinite on-site (Hubbard) repulsion, was introduced, and a simple analytical method of solving the multi-polaron problem in complex lattice structures was described.
Abstract: We introduce a generic Froehlich-Coulomb model of the oxides, which also includes infinite on-site (Hubbard) repulsion, and describe a simple analytical method of solving the multi-polaron problem in complex lattice structures. Two particular lattices, a zig-zag ladder and a perovskite layer, are studied. We find that depending on the relative strength of the Froehlich and Coulomb interactions these systems are either polaronic Fermi (or Luttinger)-liquids, bipolaronic superconductors, or charge segregated insulators. In the superconducting phase the carriers are superlight mobile bipolarons. The model describes key features of the cuprates such as their Tc values, the isotope effects, the normal state diamagnetism, pseudogap, and spectral functions measured in tunnelling and photoemission. We argue that a low Fermi energy and strong coupling of carriers with high-frequency phonons is the cause of high critical temperatures in novel superconductors.
67 citations
TL;DR: A series of biaxially textured Ni1−xCrx materials, with compositions x=0, 7, 9, 11, and 13 at.%Cr, have been studied for use as substrate materials in coated conductor applications with high temperature superconductors as discussed by the authors.
Abstract: A series of biaxially textured Ni1−xCrx materials, with compositions x=0, 7, 9, 11, and 13 at.%Cr, have been studied for use as substrate materials in coated conductor applications with high temperature superconductors. The magnetic properties were investigated, including the hysteretic loss in a Ni–7at.%Cr sample that was controllably deformed; for comparison, the loss was also measured in a similarly deformed pure Ni substrate. Complementary X-ray diffraction studies show that thermomechanical processing produces nearly complete {1 0 0}〈1 0 0〉 cube texturing, as desired for applications.
67 citations
TL;DR: A microscopic state for the vortex phase of BSCO superconductors is proposed, where around the vortex core or above H(c2), the d wave hole pairs form a checkerboard localized in the antiferromagnetic background.
Abstract: We propose a microscopic state for the vortex phase of BSCO superconductors. Around the vortex core or above H-c2, the d wave hole pairs form a checkerboard localized in the antiferromagnetic background. We discuss this theory in connection with recent ST
TL;DR: In this paper, the synthesis of MgB2 with bulk superconducting properties by conventional solid state methods at temperatures as low as 550°C was reported, where the amount of nonstoichiometry is likely to be very small.
Abstract: We report the synthesis of MgB2 with bulk superconducting properties by conventional solid state methods at temperatures as low as 550 °C Mg deficiencies of the type Mg1−xB2 were tested Tc was found to decrease by about 1 K at large x, though the amount of nonstoichiometry, if any, is likely to be very small For specific processing conditions, indications of the 25–30 K transition often seen in thin films were seen in the bulk materials The lower temperature transition may be associated with the grain boundaries These results indicate that it should be possible to fabricate MgB2 with bulk properties in in situ thin films at temperatures of 600 °C or less
TL;DR: Analysis of both simple classical and complex quantum percolation shows how topological concepts can be used to understand many mysterious properties of high temperature superconductors, including the remarkably similar phase diagrams of La(2-x)Sr(x)CuO4 and C60(+y).
Abstract: Generic intermediate phases with anomalous properties exist over narrow composition ranges adjacent to connectivity transitions. Analysis of both simple classical and complex quantum percolation shows how topological concepts can be used to understand many mysterious properties of high temperature superconductors, including the remarkably similar phase diagrams of La(2-x)Sr(x)CuO4 and C60(+y). Predictions are made for novel threshold behavior of the impurity band metal-insulator transition in two dimensions.
TL;DR: In this paper, the authors demonstrate a novel method of effectively patterning vortex pinning sites in single crystals of the high temperature superconductors YBa 2 Cu 3 O 7-d and Bi 2 Sr 2 CaCu 2 O x using heavy ion irradiation.
Abstract: Columnar defects induced by high-energy heavy ion irradiation constitute one of the most effective vortex pinning sites in high temperature superconductors. We demonstrate a novel method of effectively patterning vortex pinning sites in single crystals of the high temperature superconductors YBa 2 Cu 3 O 7-d and Bi 2 Sr 2 CaCu 2 O x using heavy ion irradiation. These patterns include linear channels, a lattice of squares, and asymmetric pinning gradient sites where vortices can either flow unimpeded or are trapped in spatially periodic arrangements.
TL;DR: In this paper, the authors investigated the fluctuation conductivity in YBa2Cu3O7−y (YBCO) films with T≈80 K. Unlike the optimally doped samples, these films exhibit a transition from a Maki-Thompson (MT) mechanism for scattering of fluctuational pairs to a Lawrence-Doniach (LD) mechanism and, as the temperature approaches Tc, to an Aslamazov-Larkin (AL) mechanism.
Abstract: The fluctuation conductivity in YBa2Cu3O7−y (YBCO) films with T≈80 K is investigated for the first time. Unlike the optimally doped samples, these films exhibit a transition from a Maki–Thompson (MT) mechanism for the scattering of fluctuational pairs to a Lawrence–Doniach (LD) mechanism and, as the temperature approaches Tc, to an Aslamazov–Larkin (AL) mechanism. It is shown that the coherence length ξc(0) along the c axis and the phase relaxation time τφ(100 K) of the fluctuational pairs are determined by the temperature of this second transition. The features observed on both the fluctuation conductivity and resistive behavior are sharply enhanced as Tc approaches 80 K, probably because of a significant increase in the intensity of the magnetic interaction in high-Tc superconductors at these temperatures. In spite of this, for two samples a value τφ(100 K)=(3.35±0.01)×10−13 s is measured, i.e., the same value as for optimally doped YBCO films. It is shown that the dependence of ξc(0) on Tc obeys the standard theory of superconductivity. The mechanisms for the scattering of charge carriers and the superconducting pairing in YBCO are analyzed.
TL;DR: In this article, magneto-optical imaging reveals that in superconducting films of MgB2 a pulse of transport current creates avalanche-like flux dynamics where highly branching dendritic patterns are formed.
Abstract: Magneto-optical imaging reveals that in superconducting films of MgB2 a pulse of transport current creates avalanche-like flux dynamics where highly branching dendritic patterns are formed. The instability is triggered when the current exceeds a threshold value, and the superconductor, shaped as a long strip, is initially in the critical state. The instability exists up to 19 K, which is a much wider temperature range than in previous experiments, where dendrites were formed by a slowly varying magnetic field. The instability is believed to be of thermomagnetic origin indicating that thermal stabilization may become crucial in applications of MgB2.
TL;DR: In this paper, a transition from the Maki-Thompson mechanism of scattering of fluctuational pairs to the Aslamazov-Larkin mechanism as the temperature approaches Tc was investigated.
Abstract: Fluctuation conductivity in YBa2Cu3O7−y (YBCO) films with different oxygen concentrations is investigated. All of the samples exhibit a clear transition from the Maki–Thompson mechanism of scattering of fluctuational pairs to the Aslamazov–Larkin mechanism as the temperature approaches Tc. The values of the transition temperature are used to determine the coherence length ξc(0) along the c axis and the phase relaxation time τφ(100K) of the fluctuational pairs. Despite the decrease of Tc from 87.4 to 54.2 K with decreasing oxygen content in the samples studied, a value τφ(100K)=(3.35±0.01)×10−13 s is obtained for all the samples. It is shown that the dependence of ξc(0) on Tc conforms to the standard theory of superconductivity. The mechanisms for the scattering of charge carriers and for superconducting pairing in high-Tc superconductors are analyzed.
TL;DR: In this article, the flux pinning in melt-textured (Nd0.33Sm 0.33)Ba2Cu3Oy NSG-123 superconductors with various numbers of Gd2BaCuO5 (Gd-211) particles was studied.
Abstract: We have studied the flux pinning in melt-textured (Nd0.33Sm0.33Gd0.33)Ba2Cu3Oy NSG-123 superconductors with various numbers of Gd2BaCuO5 (Gd-211) particles. Transmission electron microscopy (TEM) showed that submicron Gd-211 particles are uniformly distributed in the superconductive matrix. Dark-field TEM observations further showed that a high density of RE rich RE1+xBa2−xCu3Oy (RE-123ss) clusters 3–10 nm in size were distributed in the NSG-123 matrix. A strongly developed fishtail was observed in the magnetization hysteresis loops of all the samples. A critical current density of 100 kA/cm2 (77 K) was achieved at the secondary peak field of 2 T for the H∥ c axis in the NSG-123 sample with 10 mol % Gd-211. Large grain NSG-123 pellets with 30 mol % Gd-211 and 20 wt % AgO2, 30 mm in diameter and 15 mm in height, exhibited a single-cone profile with a peak value of 1.2 T at 77 K. A higher trapped-field value of 1.5 T was recorded at 2 T, reflecting the secondary peak effect.
TL;DR: The structural properties and superconductivity of Mg(B1−xCx)2 compounds were investigated by means of powder x-ray diffraction (XRD) and magnetization measurements.
Abstract: The structural properties and superconductivity of Mg(B1−xCx)2 compounds were investigated by means of powder x-ray diffraction (XRD) and magnetization measurements. Powder XRD Rietveld analysis indicates that the samples crystallize in a hexagonal AlB2-type structure. The lattice parameter a decreases slightly with increasing carbon content, while c remains unchanged. The addition of carbon results in a decrease of TC and an increase in the superconducting transition width, while the critical current density Jc data indicate that MgB1.8C0.2 manifests comparable superconducting properties with MgB2.
TL;DR: In this paper, a thin interlayer is incorporated in ramp-type Josephson junctions to obtain an increased transparency, restoring the surface damaged by ion milling and leading to clean and well-defined interfaces.
Abstract: A thin interlayer is incorporated in ramp-type Josephson junctions to obtain an increased transparency. The interlayer restores the surface damaged by ion milling and has the advantage of an all in situ barrier deposition between two superconductors, leading to clean and well-defined interfaces. The method has been applied to Josephson junctions between high (YBa2Cu3O7–) and low temperature (Nb) superconductors, separated by a Au barrier. Transmission electron microscopy images of these junctions reveal crystalline YBa2Cu3O7– up to the interface with the Au barrier. The junctions have improved critical current density values exceeding 20 kA/cm2, normal state resistances of 3×10–8 cm2 and IcRn products of 0.7 mV at 4.2 K. Furthermore, the junction properties can be controlled by varying the Au barrier thickness.
Book•
31 Jul 2002
TL;DR: In this article, the Bisoliton model of high-TC superconductivity was used to predict tunneling measurements in Cuprates. But it was not shown to be the case for all Cuprates and their basic properties.
Abstract: Preface. 1. Introduction. 2. The BCS Model of Superconductivity in Metals. 3. Cuprates and Their Basic Properties. 4. Cuprates: Anomaly in Tunneling Spectra. 5. Nonlinear Excitations: Solitons. 6. Evidence for Soliton-Like Excitations in Cuprates. 7. Bisoliton Mode of High-TC Superconductivity. 8. The Bisoliton Model and Data. 9. The Mechanism of C-Axis Phase Coherence. 10. The Mechanism of High-TC Superconductivity. 11. High-TC Superconductivity Could be Predicted. 12. Analysis of Tunneling Measurements in Cuprates. References. Index.
01 Jan 2002
TL;DR: In this paper, the authors proposed a new phase-sensitive test of order parameter symmetry for cuprate superconductivity, which is based on the Ginzbaum-Landau model.
Abstract: Preface. Part I: Cuprate superconductivity. Growth and doping of MBE prepared cuprate films I. Lagues, et al. Growth of a hard-grown single crystal-Bi2SR2Ca2O10+delta C.T. Lin, B. Liang. Exchange and spinfluctuation pairing in the two-band Hubbard model Applications to cuprate N.M. Plakida. High temperatures superconductors in high frequency fields C.T. Rieck, K. Scharnberg. Stripe-like inhomogeneities, carriers, and BCS-BEC crossover in the high Tc cuprates J. Ashkenazi. Charge- and spin-density-wave superconductors: Psuedogap puzzle in the cuprates A.M. Gabovich, et al. Strong-coupling superconductivity with d-wave order parameter and s-wave gap applications to cuprates A.S. Alexandrov. Theory of BSCCO bicrystal C-axis twist Josephson junctions: a new phase-sensitive test of order parameter symmetry R.M. Klemm. Time reversal breaking states and spontaneous current patterns in Josephson junction of d-wave superconductors M.H.S. Amin. Electronic thermal conductivity of partially-gapped CDW superconductors M. Ausloos. Peculiarities of the spectrum of strongly correlated electrons A. Sherman, M. Schreiber. Pair-transfer superconductivity on doping determined bands and the pseudogap N. Kristoffel, P. Rubin. Extended Brinkman-Rice picture and its application to high-Tc superconductors H.-T. Kim. Many band effects in superconductivity H. Nagao et al. Study on electronic specific heat of La2-XSrxCuO4: pseudogap and superconductivity N. Momono, et al. Correlation between superconducting gap and pseudogap in High-Tc cooperates M. Oda, et al. High spin paramagnetic centers in tetragonal phase of Er123, Dy123, and (er,Y)123 compounds V. Likodimos, et al. EPR study of spin clusters in oxygen deficient R123 compounds V. Likodimos, et al. Part II: Novel superconductors. Superconductivity in pure and electron-doped MgB2: transport properties and pressure effects B. Lorenz, et al. Superconductivity gap and electron-phonon interaction in MgB2 thin film studied by point contact N.L. Bobrov. A two-band approach to MgB2 superconductivity T. Ord, N. Kristoffel. Specific heat and disorder in the mixed state of non-magnetic borocarbides and a comparison with exotic superconductors D. Lipp, et al. On the influence of a non-local electrodynamics in the irreversible magnetization of non-magnetic borocarbides A.V. Silhanek. Spontaneous spin polarization and electronic states in platinum nano-particles towards compacted superconductivity H. Hori. Calculation of correlation functions for superconductivity models N.N. Bogolubov. Theoretical analysis of the symmetry of the order parameter in unconventional superconductors: singlet versus triplet pairing D. Manske. P-wave pairing in superconducting Sr2RuO4 Litak. High temperatures superconductivity of semi-localized 2D electron system with circular molecular orbits M. Sugahara. Two- particle green function in the theory of superconductivity of HTSC and C60 crystals A.M. Yaremko. Part III: Mesoscopic Superconductors. Vortex structure in mesoscopic superconductors F.M. Peeters, B.J. Baelus. Quantum measurement of charge and flux qubits Y. Makhlin. Nanostructured superconductor/ferromagnet bilayers M. Lange, et al. Half-integer number vortices in the Ginzburg-Landau-Higgs model G. Stenuit, et al. The hydrodynamic instability in the
TL;DR: In this article, the microwave power and frequency dependence of the surface resistance of MgB2 films and powder samples were studied, and it was shown that the performance of high-quality YBCO films was comparable to that of high quality Mgb2 films at all temperatures.
Abstract: The microwave power and frequency dependence of the surface resistance of MgB2 films and powder samples were studied Sample quality is relatively easy to identify by the breakdown in the ω2 law for poor-quality samples at all temperatures The performance of MgB2 at 10 GHz and 21 K was compared directly with that of high-quality YBCO films The surface resistance of MgB2 was found to be approximately three times higher at low microwave power and showed an onset of nonlinearity at microwave surface fields ten times lower than the YBCO film It is clear that MgB2 films are not yet optimized for microwave applications
TL;DR: In this paper, a hybrid magnetic vehicle using permanent magnets and high temperature superconductor (HTS) bulks is presented, where the HTS bulks provide partial levitation force and guidance force and the onboard permanent magnets provide additional levitation forces.
Abstract: A hybrid maglev vehicle using permanent magnets and high temperature superconductor (HTS) bulks is presented. Its guideway is composed of permanent magnets and soft iron. The HTS bulks provide partial levitation force and guidance force, and the onboard permanent magnets provide additional levitation force. Firstly, the levitation force of a single permanent magnet and a single HTS bulk over a permanent magnetic track is studied, the surface magnetic flux density of which is up to 1.2 T. Secondly, both levitation force and guidance force of two arrays of permanent magnets and HTS bulks are studied. Results show that the hybrid maglev vehicle using permanent magnets and HTS bulks has larger levitation force and stiffness.
TL;DR: In this article, the quantum voltages of an array of YBa2Cu3O7 bicrystal junctions were calibrated against a programmable Josephson array voltage standard.
Abstract: Quantum voltages of an array of YBa2Cu3O7 bicrystal junctions were calibrated against a programmable Josephson array voltage standard. We demonstrated that steps of the current–voltage characteristic of an array of bicrystal junctions at voltages of about 9 mV were flat over the current range of about 80 μA to within six parts in 108. The coincidence of quantum voltages on the array of high-temperature superconductor junctions at 64 K and the reference voltage on the array of niobium junctions at 4.2 K was measured with an uncertainty of two parts in 108. With the same uncertainty, we revealed the coincidence of the Josephson constant KJ≡h/2e in YBa2Cu3O7 and in metallic superconductors.
TL;DR: In this paper, the effect of magnetic flux creep on the levitation stability of high-temperature superconductors was studied and the theory of relaxation of magnetization and force for a partial and full penetration of the critical state was considered.
TL;DR: In this paper, the effect of Al doping on superconductivity of MgB2 samples was investigated by means of resistivity-temperature (R-T) and ac susceptibility-tope temperature (χ-T).
Abstract: Mg1−xAlxB2 samples in the region of 0
01 Jan 2002
TL;DR: In this article, it was shown that tunneling between a superconductor and a normal metal allowed a direct measurement of the quasiparticle density of states in the superconductuctor.
Abstract: The discovery of the high temperature superconductors in 1986 radically changed the situation in the field of superconductivity. Not only did the critical temperature increase drastically, but it becomes more and more clear that the nature of the superconducting state in the high temperature superconductors is radically different from the one found in the well known low temperature superconductors. In spite of a considerable world wide effort to study these new superconductors we still do not know the origin and the nature of the pairing interaction. It remains one of the central challenges of solid state physics today to elucidate this mechanism. One essential ingredient in the quest for an understanding of the superconducting state is the quasiparticle density of states or in other words the density of single particle excitations above the superconducting ground state. In 1960 Ivar Giaever 2 demonstrated that tunneling between a superconductor and a normal metal allowed a direct measurement of the quasiparticle density of states in the superconductor. After this path breaking work, tunneling became a main tool for investigating the various low temperature superconducting materials known at the time. In particular the inversion scheme developed by Rowell and McMillan to extract the electron phonon coupling from the tunneling spectra made a quantitative verification of the BCS model for these low temperature materials possible. Since the discovery of the high temperature superconductors, numerous investigations have been carried out with the hope that such tunneling studies will finally allow to unravel the mechanisms leading to high
TL;DR: In this article, photoelastic modulation and hetrodyne detection were used to simultaneously measure the Faraday rotation and induced ellipticity in light transmitted by semiconducting and metallic samples.
Abstract: A sensitive polarization modulation technique uses photoelastic modulation and hetrodyne detection to simultaneously measure the Faraday rotation and induced ellipticity in light transmitted by semiconducting and metallic samples. The frequencies measured are in the mid-infrared and correspond to the spectral lines of a CO2 laser. The measured temperature range is continuous and extends from 35 to 330K. Measured samples include GaAs and Si substrates, gold and copper films, and YBCO and BSCCO high temperature superconductors.