Fermi surface of the electron-doped cuprate superconductor Nd_2−xCe_xCuO₄probed by high-field magnetotransport

Abstract

We report on the study of the Fermi surface of the electron-doped cuprate superconductor Nd 2−x Ce x CuO 4 by measuring the interlayer magnetoresistance as a function of the strength and orientation of the applied magnetic field. We performed experiments in both steady and pulsed magnetic fields on high-quality single crystals with Ce concentrations of x = 0.13 to 0.17. In the overdoped regime of x > 0.15 we found both semiclassical angle-dependent magnetoresistance oscillations (AMRO) and Shubnikov-de Haas (SdH) oscillations. The combined AMRO and SdH data clearly show that the appearance of fast SdH oscillations in strongly overdoped samples is caused by magnetic breakdown. This observation provides clear evidence for a reconstructed multiplyconnected Fermi surface up to the very end of the overdoped regime at x 0.17. The strength of the superlattice potential responsible for the reconstructed Fermi surface is found to decrease with increasing doping level and likely vanishes at the same carrier concentration as superconductivity, suggesting a close relation between translational symmetry breaking and superconducting pairing.A detailed analysis of the high-resolution SdH data allowed us to determine the effective cyclotron mass and Dingle temperature, as well as to estimate the magnetic breakdown field in the overdoped regime.

Intermediate coupling model of the cuprates

“…apparent crossover to the large LDA FS (second topological transition) at 17% doping, Fig. 14. An extension to lower doping, x=0.13, was unable to find QOs below 15% doping, again consistent with the first topological transition [129]. It is surprising that QOs associated with the electron pockets have not been observed, but they are expected to be fairly weak.…”

“…12. While the early QO measurements [128] reported the large FS at x=0.17, more recent measurements find that this is a magnetic breakdown effect [129,130] with a small but finite residual gap of ∼ 14 meV for [From Ref. [128].]…”

Correlation between Fermi surface transformations and superconductivity in the electron-doped high-TcsuperconductorNd2−xCexCuOHelm1, Kartsovnik2, Proust3 et al. 2015Phys. Rev. B496520View full textAdd to dashboardCite

“…18 The fast β oscillations reveal a cyclotron orbit, which is geometrically equivalent to that on the large unreconstructed Fermi surface and arises from the MB effect. 19,20,26 The fast oscillations are dominant at high fields for x = 0.17 and rapidly diminish at decreasing doping. For x = 0.15, they are about 100-times weaker than the slow oscillations at the same field strength.…”

“…Magnetotransport studies go even further, indicating the presence of two types of charge carriers [11][12][13][14][15][16][17][18][19][20] and, hence, a reconstructed Fermi surface even in the overdoped region of the phase diagram. Based on the normal-state Hall and Seebeck effects in Ln = Pr thin films a quantum critical point (QCP) associated with the Fermi surface reconstruction was proposed to lie under the SC dome in the overdoped range of the phase diagram.…”

“…between x opt and x c . However, subsequent more elaborate SdH experiments 19,20 have further extended the range in which the Fermi surface stays reconstructed up to at least x = 0.17, the highest (though still SC) doping level attainable in bulk NCCO crystals. Thus, while the existence of one or even more critical points associated with a Fermi surface reconstruction in the electron-doped cuprates is generally accepted, 1,22-24 the question about their location with respect to the SC part of the phase diagram and their possible relation to the SC pairing remains open.…”