Metal-to-insulator crossover and pseudogap in single-layerBi2+xSr2−xCu1+<

Abstract

The in-plane ρ ab (H) and the out-of-plane ρc(H) magneto-transport in magnetic fields up to 28 T has been investigated in a series of high quality, single crystal, hole-doped La-free Bi2201 cuprates for a wide doping range and over a wide range of temperatures down to 40 mK. With decreasing hole concentration going from the overdoped (p=0.2) to the underdoped (p=0.12) regimes, a crossover from a metallic to and insulating behavior of ρ ab (T ) is observed in the low temperature normal state, resulting in a disorder induced metal insulator transition. In the zero temperature limit, the normal state ratio ρc(H)/ρ ab (H) of the heavily underdoped samples in pure Bi2201 shows an anisotropic 3D behavior, in striking contrast with that observed in La-doped Bi2201 and LSCO systems. Our data strongly support that that the negative out-of-plane magnetoresistance is largely governed by interlayer conduction of quasiparticles in the superconducting state, accompanied by a small contribution of normal state transport associated with the field dependent pseudogap. Both in the optimal and overdoped regimes, the semiconducting behavior of ρc(H) persists even for magnetic fields above the pseudogap closing field Hpg. The method suggested by Shibauchi et al. (Phys. Rev. Lett. 86, 5763, (2001)) for evaluating Hpg is unsuccessful for both under-and overdoped Bi2201 samples. Our findings suggest that the normal state pseudogap is not always a precursor of superconductivity.

Vortexlike excitations in a nonsuperconducting single-layer compoundBi2+xSr2−xCuO6+δVedeneev1, Maude2 2005Phys. Rev. BSelf Cite184110View full textAdd to dashboardCite

“…In previous measurements 15 we have investigated the in-plane ρ ab (H, T ) and the out-of-plane ρ c (H, T ) magneto-transport in magnetic fields up to 28 T in a series of superconducting Bi2201 single crystals over a wide doping range and over a wide range of temperatures down to 40 mK. The T c (midpoint) values of the crystals lay in the region 2.3 − 9.6 K. With decreasing carrier concentration per Cu atom (p), going from the overdoped (p = 0.2) to the underdoped (p = 0.12) regimes, a crossover from a metallic to an insulating behavior of ρ ab (T ) was observed in the low temperature normal state, resulting from a disorder induced metal insulator transition.…”

c-axis longitudinal magnetoresistance of the electron-doped superconductorPr1.85Ce0.15CuOYu1, Liang2, Greene3 2006Phys. Rev. B4140View full textAdd to dashboardCite

“…C-axis transport is also a good probe of the electron density of states (DOS) at the Fermi surface close to (π, 0) in the tetragonal cuprates 4,5 , because of its intrinsic interlayer tunneling nature and a transfer integral effect. A pseudogap, indicated by a loss of electronic DOS, has been observed by c-axis transport in both the p-type 6,7,8,9,10,11,12,13 and the n-type cuprates 14 . However, from the evidence to date it is not clear if the pseudogaps in the two systems are of the same origin.…”

“…A small-energy gap is consistent with a precursor pairing or superconducting fluctuation scenario 6,7,8,19 . A large-energy pseudogap opens at (π, 0), which is unlikely to be correlated with superconductivity although the origin is still being debated 8,9,10,11,12,13 .…”

Fermi surface of underdoped cuprate superconductors from interlayer magnetoresistance: Closed pockets versus open arcs

“…However, previous IMR measurements made at high magnetic field [40][41][42][43] have not revealed a strong anisotropy. We address this discrepancy below, first noting that the observation of QOs in underdoped systems was made only in the past 4 years ͑as was the corresponding observation in overdoped systems, which reveal a large normal-metallic FS͒ and the improvements in sample quality that made this possible could usher in a new generation of IMR measurements as well.…”

“…42,43 Among suggestions made to explain this phenomenon, a field-dependent pseudogap ͑⌬ 0 decreases with B due to Zeeman effects͒ has been proposed. The primary effect of a field-dependent gap ⌬ 0 is an isotropic drop in the magnitude of zz ͑B͒.…”