https://repository.library.northeastern.edu/files/neu:331186/fulltext.pdf

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

Classical BCS superconductive couplings leading to small Tc‘s rely on phonon mediated weak coupling of delocalized electrons in three dimensional structures. Attempts to produce or explain higher Tc have considered the breakdown of one or several of these hypotheses. The possible role of quasilowdimensionality for delocalized electrons will be stressed, and the potential superiority of fine mesh three dimensional networks of chain conductors argued from that point of view.

https://iopscience.iop.org/article/10.1088/0953-8984/1/42/001/pdf

The high-Tc superconductors: a conservative view

After a mention of the structural, magnetic and electronic properties of high-temperature superconductors (HTSC), the basic principles of NMR-NQR experiments in these compounds are presented, emphasizing the marked differences and the novel aspects of the latter systems in comparison with metals and conventional superconductors. It follows a review of NMR-NQR spectra and relaxation rates in two-dimensional quantum antiferromagnets (particularly ) driven towards the superconducting state by charge doping. The main results obtained in the normal state of HTSC are summarized, while the problems of the spin-gap and of the superconducting fluctuations are discussed to a certain extent, by including the most recent contributions. An overview is given on the main conclusions derived from NMR-NQR experiments in the superconducting state. A section is devoted to the insights into the vortex lattice and the flux lines motion that have been obtained from NMR line narrowing, and echo dephasing. This review deals mostly with three systems, , and .

http://iopscience.iop.org/article/10.1088/0034-4885/61/10/002/pdf

Basic aspects and main results of NMR-NQR spectroscopies in high-temperature superconductors

The high-Tcsuperconductors: a conservative view

The magnetic behaviour of La2-xSrxCuO4 was studied using the method of muon spin rotation (μSR) We found that the system orders magnetically for x ≤ 005 and the Neel-temperatures vary from 250 K for x = 0 to 6 K for x = 005 In spite of these drastic changes of the Neel-temperatures, the extrapolated internal fields at T = 0 K are similar for all samples indicating that the moments at the magnetic (Cu) ions are not changed appreciably The depolarization rates measured in this experiment are analyzed in terms of an inhomogeneous field distribution in the sample

https://iopscience.iop.org/article/10.1209/0295-5075/5/7/014/pdf

Dependence of the Nèel-Temperatures of La2CuO4 on Sr-Doping Studied by Muon Spin Rotation

Nuclear quadrupole resonance (NQR) of 139 La has been performed to study the electronic and magnetic properties of La 2- x Ba x CuO 4 between 1.5 and 240 K. The temperature dependence of the separation of the double peaks in spectra clearly indicates the magnetic ordering in the small x region. The internal fields at La sites due to magnetic order largely decrease with Ba concentration. The divergence of 1/ T 2 indicates that another phase appears at low temperatures. The electric field gradient changes on passing from the normal to the superconducting states, indicating the apparent influence of superconductivity on the electronic state at La sites in this system.

Evidence of Successive Magnetic Transition in La2-xBaxCuO4 –NQR Studies of 139La–

Nuclear quadrupole resonance (NQR) of 139La has been performed to study magnetic properties of La2-xBaxCuO4 between 1.4 and 250 K. The pronounced enhancement of nuclear relaxation rates of 1/T2 and 1/T1 are obtained for 0.01

Toshinori Kimura

Papers

Evidence of Successive Magnetic Transition in La2-xBaxCuO4 –NQR Studies of 139La–

NQR studies on magnetic properties of La2−xBaxCuO4