scholarly journals Temperature-Independent Cuprate Pseudogap from Planar Oxygen NMR

2020 ◽  
Vol 5 (4) ◽  
pp. 66 ◽  
Author(s):  
Jakob Nachtigal ◽  
Marija Avramovska ◽  
Andreas Erb ◽  
Danica Pavićević ◽  
Robin Guehne ◽  
...  
Keyword(s):  
Fermi Liquid ◽  
Exchange Coupling ◽  
Cuprate Superconductors ◽  
Nmr Relaxation ◽  
Nuclear Relaxation ◽  
Specific Heat Data ◽  
Optimal Doping ◽  
Gap States ◽  
Shift Data ◽  
Heat Data

Planar oxygen nuclear magnetic resonance (NMR) relaxation and shift data from all cuprate superconductors available in the literature are analyzed. They reveal a temperature-independent pseudogap at the Fermi surface, which increases with decreasing doping in family-specific ways, i.e., for some materials, the pseudogap is substantial at optimal doping while for others it is nearly closed at optimal doping. The states above the pseudogap, or in its absence are similar for all cuprates and doping levels, and Fermi liquid-like. If the pseudogap is assumed exponential it can be as large as about 1500 K for the most underdoped systems, relating it to the exchange coupling. The pseudogap can vary substantially throughout a material, being the cause of cuprate inhomogeneity in terms of charge and spin, so consequences for the NMR analyses are discussed. This pseudogap appears to be in agreement with the specific heat data measured for the YBaCuO family of materials, long ago. Nuclear relaxation and shift show deviations from this scenario near Tc, possibly due to other in-gap states.

The Solid Solution CeAuIn1–xMgx – Structure, Magnetic Properties and Specific Heat Data

2006 ◽  
Vol 61 (5) ◽  
pp. 495-502 ◽  
Author(s):  
Sudhindra Rayaprol ◽  
Birgit Heying ◽  
Rainer Pöttgen
Keyword(s):  
Solid Solution ◽  
Fermi Liquid ◽  
Induction Furnace ◽  
Magnetic Ordering ◽  
Magnesium Concentration ◽  
Crystal Data ◽  
Specific Heat Data ◽  
X Ray ◽  
The Difference ◽  
Heat Data

Four different samples of the solid solution CeAuIn1−xMgx with x = 0.2, 0.4, 0.6, and 0.8 have been prepared from the elements in sealed tantalum tubes in an induction furnace. The samples were characterized through X-ray powder and single crystal data: ZrNiAl type, P6̅2m, Z = 3, a = 774.54(7), c = 420.32(10) pm, wR2 = 0.0203, 395 F2 values, 15 variables for CeAuIn0.871Mg0.129, a = 775.25(7), c = 419.36(10) pm, wR2 = 0.0488, BASF = 0.10(1), 397 F2 values, 16 variables for CeAuIn0.640Mg0.360, a = 774.62(7), c = 420.13(10) pm, wR2 = 0.0435, 376 F2 values, 15 variables for CeAuIn0.445Mg0.555, a = 773.80(11), c = 420.82(8) pm, wR2 = 0.0415, 392 F2 values, 15 variables for CeAuIn0.228Mg0.772. The lattice parameters show no pronounced changes within the solid solution. The largest shift occurs for the x parameter of the mixed occupied In/Mg positions. Due to the difference in size, the trigonal prisms around the Au1 atoms at the origin become smaller with an increasing content of magnesium. The In/Mg-In/Mg distances decrease from 334.5 (CeAuIn0.871Mg0.129) to 328.3 (CeAuIn0.228Mg0.772) pm, and consequently one observes also shorter bonds to the Au1 atoms with an increasing content of magnesium concentration. Susceptibility measurements reveal trivalent cerium for all CeAuIn1−xMgx compounds, with no evidence sign of magnetic ordering down to 2 K. The disorder created by chemical substitution destroys the longrange magnetic ordering which can be attributed to the triggering of non Fermi-liquid (NFL) like behavior.

scholarly journals EFFECTS OF c-AXIS HOPPING IN THE INTERLAYER TUNNELING MODEL OF HIGH-Tc LAYERED CUPRATES

1999 ◽  
Vol 13 (13) ◽  
pp. 1619-1632
Author(s):  
BIPLAB CHATTOPADHYAY ◽  
A. N. DAS
Keyword(s):  
Experimental Data ◽  
Transition Temperature ◽  
Cuprate Superconductors ◽  
Interlayer Coupling ◽  
Superconducting Gap ◽  
Tunneling Model ◽  
High Tc ◽  
Optimal Doping ◽  
Pair Tunneling ◽  
Layered Cuprates

We consider the interlayer pair-tunneling model for layered cuprates, including an effective single particle hopping along the c-axis. A phenomenological suppression of the c-axis hopping matrix element, by the pseudogap in cuprate superconductors, is incorporated. At optimal doping, quantities characteristic to the superconducting state, such as the transition temperature and the superconducting gap are calculated. Results from our calculations are consistent with the experimental observations with the noteworthy point that, the superconducting gap as a function of temperature shows excellent match to the experimental data. Predictions within the model, regarding T c variation with interlayer coupling, are natural outcomes which could be tested further.

Specific heat data of high-Tc superconductors: Lattice and electronic contributions

1989 ◽  
Vol 69 (6) ◽  
pp. 625-629 ◽  
Author(s):  
J.E. Gordon ◽  
M.L. Tan ◽  
R.A. Fisher ◽  
N.E. Phillips
Keyword(s):  
Specific Heat ◽  
High Tc Superconductors ◽  
Specific Heat Data ◽  
High Tc ◽  
Heat Data

scholarly journals SPECTRAL ANOMALY AND HIGH TEMPERATURE SUPERCONDUCTORS

1996 ◽  
Vol 10 (07) ◽  
pp. 805-845 ◽  
Author(s):  
LAN YIN ◽  
SUDIP CHAKRAVARTY
Keyword(s):  
High Temperature ◽  
Spectral Function ◽  
Superconducting State ◽  
Fermi Liquid ◽  
Cuprate Superconductors ◽  
High Temperature Superconductors ◽  
Universality Class ◽  
Scaling Relation ◽  
Critical System ◽  
Spectral Anomaly

Spectral anomaly for interacting fermions is characterized by the spectral function A ([k − k F ], ω) satisfying the scaling relation A (Λy1 [k − k F ], Λy2 ω) =ΛyA A ([k − k F ], ω), where y1, y2, and yA are the exponents defining the universality class. For a Fermi liquid y1 = 1, y2 = 1, yA = −1; all other values of the exponents are termed anomalous. In this paper, an example for which y1 = 1, y2 = 1, but yA = α − 1 is considered in detail. Attractive interaction added to such a critical system leads to a novel superconducting state, which is explored and its relevance to high temperature cuprate superconductors is discussed.

scholarly journals PROTON MAGNETIC RESONANCE IN PARAMAGNETIC AND ANTIFERROMAGNETIC CoCl2∙6H2O

1964 ◽  
Vol 42 (4) ◽  
pp. 657-677 ◽  
Author(s):  
E. Sawatzky ◽  
M. Bloom
Keyword(s):  
Magnetic Resonance ◽  
Crystal Orientation ◽  
Applied Field ◽  
Field Approximation ◽  
Order Effects ◽  
Zero Field ◽  
Proton Resonance ◽  
Specific Heat Data ◽  
Thermodynamic Variables ◽  
Heat Data

The transition temperature TN of CoCl2∙6H2O was measured as a function of applied field and crystal orientation using the proton resonance lines, since they are very sensitive functions of temperature near TN. TN was found to be a complicated function of the applied field and crystal orientation, which cannot be described by the molecular field approximation. The transition is gradual rather than sudden and coexistence of the NMR spectra associated with the paramagnetic and antiferromagnetic phases was observed over a temperature region of about 10−2 °K. Short-range order effects were observed near TN in the form of anomalous broadening of the magnetic resonance lines. The magnetic susceptibility in zero field was measured along the preferred axis of antiferromagnetic alignment. This, together with specific heat data from published literature, was used to show a mutual consistency between thermodynamic variables and the dependence of TN on H in low fields as obtained by NMR. The treatment follows that of Buckingham and Fairbank for the λ transition in liquid helium. The sublattice magnetization in the antiferromagnetic phase was measured as a function of temperature. It was found to depend logarithmically on (TN – T), for all values of applied field.

scholarly journals Phenomenology of 63Cu Nuclear Relaxation in Cuprate Superconductors

2019 ◽  
Vol 32 (11) ◽  
pp. 3369-3376
Author(s):  
Michael Jurkutat ◽  
Marija Avramovska ◽  
Grant V. M. Williams ◽  
Daniel Dernbach ◽  
Danica Pavićević ◽  
...  
Keyword(s):  
Cuprate Superconductors ◽  
Nuclear Relaxation
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