Superconductivity under high pressure in the binary compound CaLi2 (original) (raw)
Related papers
Theoretical predictions of superconductivity in alkali metals under high pressure
Physical Review B, 2006
We calculated the superconductivity properties of alkali metals under high pressure using the results of band theory and the rigid-muffin-tin theory of Gaspari and Gyorffy. Our results suggest that at high pressures Lithium, Potassium, Rubidium and Cesium would be superconductors with transition temperatures approaching 5 − 20K. Our calculations also suggest that Sodium would not be a superconductor under high pressure even if compressed to less than half of its equilibrium volume. We found that the compression of the lattice strengthens the electron-phonon coupling through a delicately balanced increase of both the electronic and phononic components of this coupling. This increase of the electron-phonon coupling in Li is due to an enhancement of the s-p channel of the interaction, while in the heavier elements the p-d channel is the dominant component.
Physical Review Letters, 2006
Extreme pressure strongly affects the superconducting properties of ``simple'' elemental metals, like Li, K and Al. Pressure induces superconductivity in Li (as high as 17 K), while suppressing it in Al. We report first-principles investigations of the superconducting properties of dense Li, K and Al based on a recently proposed, parameter-free, method. Our results show an unprecedented agreement with experiments, assess the predictive power of the method over a wide range of densities and electron-phonon couplings, and provide predictions for K, where no experiments exist so far. More importantly, our results help uncovering the physics of the different behaviors of Li and Al in terms of phonon softening and Fermi surface nesting in Li.
Effect of Pressure on Superconducting Properties
Journal of Superconductivity and Novel Magnetism, 2015
It is shown that the existence of superconductivity in a material, and its critical temperature, depends strongly on pressure. Several parameters are pressuredependent: (1) structure, particularly bond distances, (2) Hubbard U , (3) coupling between sites, and (4) orbital occupation number. Eliashberg theory often leads to incorrect predictions, for example in A 3 C 60 with A = K, Rb, and Cs. While T C is correctly predicted to be higher for Rb 3 C 60 than for K 3 C 60 and decreasing with pressure in both cases, Cs 3 C 60 is not superconducting at ambient pressure. The same is the case for pure metals such as Cs and Ca (superconducting at high pressure). A theory for electron pairs, similar to the Marcus model for single electrons, appears to agree with the experiment in most cases.
1996
Using a cryogenic diamond anvil cell ~DAC! the pressure dependence of the superconducting transition temperatureTc of Tl 2Ba2Ca2Cu3O101y ~Tl-2223! and Tl2Ba2Ca3Cu4O121y ~Tl-2234! has been measured resistively up to 21 GPa. At ambient pressure these compounds have Tc’s of 128.5 K and 113 K. At low pressures, the pressure dependence ]Tc /]p is 1.75 K/GPa in Tl-2223 and 2.0 K/GPa in Tl-2234. As pressure is increasedTc continues to increase ~although the rate diminishes ! until Tc reaches a maximum of 133 K at 4.2 GPa in Tl-2223 and of 120 K at 6.6 GPa in Tl-2234. At higher pressures Tc decreases. In this region a rather abrupt change in]Tc /]p is observed at pc512.0 GPa in Tl-2223 and at pc510.5 GPa in Tl-2234. The kink at pc is interpreted as an indication of the presence of inequivalentCuO2 layers: Belowpc the Tc of the samples is determined by the intrinsic Tc of the outer CuO2 layers while abovepc it is determined by that of the inner CuO2 layers.@S0163-1829 ~96!07134-2#
Is sodium a superconductor under high pressure?
The Journal of chemical physics, 2017
Superconductivity has been predicted or measured for most alkali metals under high pressure, but the computed critical temperature (Tc) of sodium (Na) at the face-centered cubic (fcc) phase is vanishingly low. Here we report a thorough, first-principles investigation of superconductivity in Na under pressures up to 260 GPa, where the metal-to-insulator transition occurs. Linear-response calculations and density functional perturbation theory were employed to evaluate phonon distributions and the electron-phonon coupling for bcc, fcc, cI16, and tI19 Na. Our results indicate that the maximum electron-phonon coupling parameter, λ, is 0.5 for the cI16 phase, corresponding to a theoretical peak in the critical temperature at Tc≈1.2 K. When pressure decreases or increases from 130 GPa, Tc drops quickly. This is mainly due to the lack of p-d hybridization in Na even at 260 GPa. Since current methods based on the Eliashberg and McMillian formalisms tend to overestimate the Tc (especially th...
Superconductivity at 133K in Tl2Ba2Ca2Cu3O10 under high pressure
1993
The pressure dependence of the superconducting transition temperature T, of TltBa&a&usO,o+, (n-2223) has been measured under pressures up to 13 GPa ( 130 kbar ). At 4.2 GPa a maximum is observed with a T, of 133 K. This is the highest T, yet observed for any high-T, superconductor with the exception of the recently discovered mercury-based compound Hg-Ba,Ca,CusOs+, (Hg-1223). Because of some structural differences between Tl-2223 and Hg-1223, a slightly higher maximum Z', is predicted for Hg-1223. Both T. and its pressure dependence are discussed on the basis of a simple charge-transfer model.
Calculations of superconducting properties in yttrium and calcium under high pressure
Physical Review B, 2007
We have used first-principles electronic structure calculations to generate the bulk modulus as a function of volume as well as the densities of states and scattering phase shifts at the Fermi level. These quantities were used in conjunction with the rigid-muffin-tin theory of Gaspari and Gyorffy and the McMillan theory to determine the electron-phonon coupling and the superconducting transition temperature for yttrium and calcium under high pressures. Our results provide a good interpretation of the measured increase of T c in these metals.
Tc map and superconductivity of simple metals at high pressure
Physica C: Superconductivity, 2010
We calculate Tc map in region of weak electron-phonon coupling based on simple phonon spectrum. By using linear-response method and density functional theory, we calculate phonon spectra and Eliashberg functions of simple metals under pressure. Based on the evolutions of superconducting parameters of simple metals on the Tc map with increasing pressure, we find that there are two different responses to pressure for simple metals: