Substitution ofScforMginMgB2

Abstract

Here we report synthesis and characterization of Mg1−xScxB2 (0.12<x<0.27) system, with critical temperature in the range of 30>Tc>6 K. We find that the Sc doping moves the chemical potential through the 2D/3D electronic topological transition (ETT) in the σ band where the "shape resonance" of interband pairing occurs. In the 3D regime beyond the ETT we observe a hardening of the E2g Raman mode with a significant line-width narrowing due to suppression of the Kohn anomaly over the range 0<q<2kF .

Feshbach Shape Resonance in Multiband Superconductivity in Heterostructures

“…6, where the superconducting gaps in the π and in the σ band and critical temperature T c obtained by aluminium [143], carbon [183,184] and scandium [177] substitutions are reported on the same scale. These results show that the two gap behaviour is present over all the range of the Lifshitz parameter of ±400 meV around z=0.…”

Anomalous Thermal Expansion in Superconducting Mg1− x Al x B2 System

“…Multiphase behavior has already been reported for a series of Mg 1-x Al x B 2 (x 0.025) systems studied by means of synchrotron X-ray powder diffraction and 11B NMR techniques [28], in Mg 1-x Sc x B 2 (x<0.12) [30], as well as an extensive series of MgB 2-x C x systems (x .06) [31].…”

“…It has been shown [21] that the interband pairing term shows a broad resonance as expected for a superconducting Feshbach shape resonance. Experimental evidence for the 2D-3D topology cross-over in the band is indicated a frequency hardening and a line-width narrowing of the Raman E 2g mode indicating a strong reduction of the electron-phonon interaction going from 2D regime to the 3D regime through the ETT point [29,30].…”

“…The theoretical interest is now focusing in understanding the physics of interband pairing by tuning the chemical potential in the proximity to the 2D-3D topology cross-over in the band (the 2D-3D ETT) [21][22][23][24][25][26]. The chemical potential can be tuned experimentally toward the 2D-3D ETT by chemical substitutions of aluminum or scandium for magnesium [28][29][30] or carbon for boron [31].…”

Soft x-ray absorption and high-resolution powder x-ray diffraction study of superconducting Ca La1−Ba1.75−La0.25+Cu3O system

“…Indeed, recently it has been argued that electronic inhomogeneity controlled by organization of defects, lattice distortions, interface states, nanoscale phase separation in the layered oxides has substantial influence in the superconducting properties of cuprates [4][5][6][7][8][9]. This appears to be common to all layered superconductors as diborides [10][11][12][13] and more recently pnictides [14][15][16][17][18][19]. Here it should be specified that large structural differences from one cuprate family to another one hinders the investigation of what drives the T c max in these materials.…”