scholarly journals Quantitative determination of pairing interactions for high-temperature superconductivity in cuprates

2016 ◽  
Vol 2 (3) ◽  
pp. e1501329 ◽  
Author(s):  
Jin Mo Bok ◽  
Jong Ju Bae ◽  
Han-Yong Choi ◽  
Chandra M. Varma ◽  
Wentao Zhang ◽  
...  
Keyword(s):  
High Temperature ◽  
Quantitative Determination ◽  
High Temperature Superconductivity ◽  
Theoretical Calculations ◽  
Spectral Weight ◽  
Loop Current ◽  
Low Energies ◽  
Repulsive Part ◽  
D Wave

A profound problem in modern condensed matter physics is discovering and understanding the nature of fluctuations and their coupling to fermions in cuprates, which lead to high-temperature superconductivity and the invariably associated strange metal state. We report the quantitative determination of normal and pairing self-energies, made possible by laser-based angle-resolved photoemission measurements of unprecedented accuracy and stability. Through a precise inversion procedure, both the effective interactions in the attractive d-wave symmetry and the repulsive part in the full symmetry are determined. The latter is nearly angle-independent. Near Tc, both interactions are nearly independent of frequency and have almost the same magnitude over the complete energy range of up to about 0.4 eV, except for a low-energy feature at around 50 meV that is present only in the repulsive part, which has less than 10% of the total spectral weight. Well below Tc, they both change similarly, with superconductivity-induced features at low energies. Besides finding the pairing self-energy and the attractive interactions for the first time, these results expose the central paradox of the problem of high Tc: how the same frequency-independent fluctuations can dominantly scatter at angles ±π/2 in the attractive channel to give d-wave pairing and lead to angle-independent repulsive scattering. The experimental results are compared with available theoretical calculations based on antiferromagnetic fluctuations, the Hubbard model, and quantum-critical fluctuations of the loop-current order.

scholarly journals GINZBURG–LANDAU LIKE THEORY OF HIGH TEMPERATURE SUPERCONDUCTIVITY IN THE CUPRATES: EMERGENT d-WAVE ORDER

2012 ◽  
Vol 26 (10) ◽  
pp. 1230005
Author(s):  
T. V. RAMAKRISHNAN
Keyword(s):  
High Temperature ◽  
Cooper Pair ◽  
Nearest Neighbor ◽  
High Temperature Superconductivity ◽  
Transition Curve ◽  
Hole Doping ◽  
Positive Interaction ◽  
Long Wavelength ◽  
Spin Singlet ◽  
D Wave

High temperature superconductivity in the cuprates remains one of the most widely investigated, constantly surprising and poorly understood phenomena in physics. Here, we describe briefly a new phenomenological theory inspired by the celebrated description of superconductivity due to Ginzburg and Landau and believed to describe its essence. This posits a free energy functional for the superconductor in terms of a complex order parameter characterizing it. We propose that there is, for superconducting cuprates, a similar functional of the complex, in plane, nearest neighbor spin singlet bond (or Cooper) pair amplitude ψij. Further, we suggest that a crucial part of it is a (short range) positive interaction between nearest neighbor bond pairs, of strength J′. Such an interaction leads to nonzero long wavelength phase stiffness or superconductive long range order, with the observed d-wave symmetry, below a temperature Tc~z J′ where z is the number of nearest neighbors; d-wave superconductivity is thus an emergent, collective consequence. Using the functional, we calculate a large range of properties, e.g., the pseudogap transition temperature T* as a function of hole doping x, the transition curve Tc(x), the superfluid stiffness ρs(x, T), the specific heat (without and with a magnetic field) due to the fluctuating pair degrees of freedom and the zero temperature vortex structure. We find remarkable agreement with experiment. We also calculate the self-energy of electrons hopping on the square cuprate lattice and coupled to electrons of nearly opposite momenta via inevitable long wavelength Cooper pair fluctuations formed of these electrons. The ensuing results for electron spectral density are successfully compared with recent experimental results for angle resolved photo emission spectroscopy (ARPES), and comprehensively explain strange features such as temperature dependent Fermi arcs above Tc and the "bending" of the superconducting gap below Tc.

Experimental Determination of Line Strengths for Selected Carbon Monoxide and Carbon Dioxide Absorption Lines at Temperatures between 295 and 1250 K

1994 ◽  
Vol 48 (11) ◽  
pp. 1442-1450 ◽  
Author(s):  
Patrick J. Medvecz ◽  
Kenneth M. Nichols
Keyword(s):  
Fourier Transform ◽  
High Temperature ◽  
Absorption Spectra ◽  
High Temperatures ◽  
Room Temperature ◽  
Theoretical Calculations ◽  
Line Strength ◽  
Temperature Data ◽  
Line Strengths

Fourier transform infrared absorption spectroscopy has been used for the determination of the line strengths of 41 CO and CO2 absorption lines at temperatures between 295 and 1250 K. The CO vibrational-rotational lines were from the P branch of the fundamental absorption band (2150–1950 cm−1) while the CO2 vibrational-rotational lines were from the far wing of the R branch of the v3 fundamental band (2395–2380 cm−1). The intensities of the lines were measured from absorption spectra recorded in a high-temperature gas cell containing known concentrations of CO/CO2/N2 gas mixtures at atmospheric pressure. Absorption spectra were recorded through the cell with the use of a moderate-resolution Fourier transform infrared spectrometer. The absorption spectra were mathematically corrected for distortions resulting from the finite resolution of the spectrometer and for peak overlap. Line strength measurements were made from the corrected peaks by using the Bouguer-Lambert law and assuming a Lorenztian line profile. The experimentally obtained line strengths were evaluated (1) by statistical calculations, (2) by consideration of the validity of the Bouguer-Lambert assumption for these data, (3) by comparison with existing room-temperature and high-temperature data, and (4) by comparison with theoretical calculations. For CO, the statistical analysis suggests that the reported values have an uncertainty of ±10–12%, which is similar to the observed discrepancies with other reported values at room temperature. At high temperatures, the difference between these data and previously reported data and theoretical predictions is less than 10%. For CO2, the statistical uncertainty associated with the line strength calculations is less than 5%, which is also the approximate level of agreement with existing room-temperature data. For lines with m indicies of 65–89, at high temperatures, the values reported in this work agree within 5 to 10% of theoretical calculations.

High-temperature superconductivity with d-wave symmetry of the order parameter (Review Article)

1998 ◽  
Vol 24 (11) ◽  
pp. 771-781 ◽  
Author(s):  
G. G. Sergeeva ◽  
Yu. P. Stepanovskiı̆ ◽  
A. V. Chechkin
Keyword(s):  
High Temperature ◽  
Order Parameter ◽  
High Temperature Superconductivity ◽  
Review Article ◽  
Wave Symmetry ◽  
D Wave

scholarly journals High-temperature superconductivity in sulfur hydride evidenced by alternating-current magnetic susceptibility

2019 ◽  
Vol 6 (4) ◽  
pp. 713-718 ◽  
Author(s):  
Xiaoli Huang ◽  
Xin Wang ◽  
Defang Duan ◽  
Bertil Sundqvist ◽  
Xin Li ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Magnetic Susceptibility ◽  
High Temperature ◽  
High Temperature Superconductivity ◽  
Theoretical Calculations ◽  
Meissner Effect ◽  
Alternating Current ◽  
Superconducting Phase ◽  
Electron Phonon Interaction

ABSTRACT The search for high-temperature superconductivity is one of the research frontiers in physics. In the sulfur hydride system, an extremely high Tc (∼200 K) has been recently developed at pressure. However, the Meissner effect measurement above megabar pressures is still a great challenge. Here, we report the superconductivity identification of sulfur hydride at pressure, employing an in situ alternating-current magnetic susceptibility technique. We determine the superconducting phase diagram, finding that superconductivity suddenly appears at 117 GPa and Tc reaches 183 K at 149 GPa before decreasing monotonically with increasing pressure. By means of theoretical calculations, we elucidate the variation of Tc in the low-pressure region in terms of the changing stoichiometry of sulfur hydride and the further decrease in Tc owing to a drop in the electron–phonon interaction parameter λ. This work provides a new insight into clarifying superconducting phenomena and anchoring the superconducting phase diagram in the hydrides.

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