Electronlike Fermi surface and remnant(π,0)feature in overdopedLa1.78

Abstract

We have performed an angle-resolved photoemission study of overdoped La1.78Sr0.22CuO4, and have observed sharp nodal quasiparticle peaks in the second Brillouin zone that are comparable to data from Bi2Sr2CaCu2O 8+δ . The data analysis using energy distribution curves, momentum distribution curves and intensity maps all show evidence of an electron-like Fermi surface, which is well explained by band structure calculations. Evidence for many-body effects are also found in the substantial spectral weight remaining below the Fermi level around (π,0), where the band is predicted to lie above EF .PACS numbers: 74.25.Jb, 71.18.+y, 74.72.Dn, 79.60.Bm Studies of low lying excitations and the Fermi surface in the high temperature superconductors by angle resolved photoemission spectroscopy (ARPES) have mostly been focused on Bi 2 Sr 2 CaCu 2 O 8+δ (BSCCO) 1-6 and YBa 2 Cu 3 O 7−y (YBCO) 7 . In these systems, however, additional features derived from complicated crystal structures, such as the Bi-O superstructures in BSCCO and the Cu-O chains in YBCO, have made the analysis rather complicated. In particular, the Bi-O superstructure complicates the interpretation of spectra around (π,0), resulting in the controversy over the Fermi surface geometry 1-6 . La 2−x Sr x CuO 4 (LSCO), by virtue of the absence of these effects and the availability of high quality single crystal samples over the entire doping range, provides the opportunity to advance our understanding of the high temperature superconductors. In the underdoped regime, earlier studies have uncovered the presence of two electronic components 8-10 , a systematic suppression of the spectral weight near (π/2, π/2) (when compared with that of overdoped samples or BSCCO for data taken under the same conditions), and straight Fermi surface segments near (π,0) of width ∼ π/2 11,12 , which have been interpreted as evidence for electronic inhomogeneities. In the overdoped regime, an electronlike Fermi surface was observed in the high-T c superconductors for the first time 8 , but despite this progress, important problems remain. Since ARPES data from underdoped samples are very broad, worries about the sample quality persist. There are also questions about the effects of the photoemission matrix element 13 , which makes it difficult to extract quantitative information about stripe effects on nodal spectral weight by comparing the experiments and theoretical calculations that predict suppression [14][15][16] . We address these important questions by performing a detailed study of overdoped LSCO (x= 0.22) where the stripe effects are expected to be weak, and have the aid of reliable band structure calculations (unlike the case of BSCCO). We performed ARPES in three Brillouin zones (BZ) and performed numerical simulations to investigate the matrix element effects. In the second BZ, using a favorable polarization, we have identified a sharp spectral feature along the diagonal direction in this sample that is comparable to that of BSCCO. This observation demonstrates that the ...

Role of the van Hove singularity in the quantum criticality of the Hubbard model

“…Matrix element effects 75,76 , and the low precision of inverse photoemission can complicate the direct measurement of the flat dispersion resulting in the van Hove singularity, making indirect probes like the Fermi surface topology 74,77 and transport measurements more important. The van Hove singularity and the quantum critical point will also impact the transport properties of the system.…”

Colloquium: Saturation of electrical resistivity

“…For a quasi-two-dimensional system, like the high-T c cuprates, we instead assume a cylindrical Fermi surface with the height 2π/c and radius k F , where c is the average separation of the CuO 2 planes. Based on photoemission results (Ino et al, 1999;Yoshida et al, 2001), we assume a "large" Fermi surface containing roughly one electron or hole (more precisely 1 ± x carriers, where x is the doping). This leads to k F = √ 2π/a, where a is the lattice parameter of the CuO 2 plane.…”

Hidden Fermi-liquid Charge Transport in the Antiferromagnetic Phase of the Electron-Doped Cuprate Superconductors

“…Moreover, below a compound specific doping level, the low-temperature resistivity for both types of cuprates develops a logarithmic upturn that appears to be related to disorder, yet whose microscopic origin has remained unknown [1,[5][6][7]. In contrast, at high dopant concentrations, the cuprates are good metals with welldefined Fermi surfaces and clear evidence for Fermi-liquid (FL) behavior [8][9][10][11][12][13][14].…”

“…Moreover, below a compound specific doping level, the low-temperature resistivity for both types of cuprates develops a logarithmic upturn that appears to be related to disorder, yet whose microscopic origin has remained unknown [1,[5][6][7]. In contrast, at high dopant concentrations, the cuprates are good metals with welldefined Fermi surfaces and clear evidence for Fermi-liquid (FL) behavior [8][9][10][11][12][13][14].In a new development, the hole-doped cuprates were found to exhibit FL properties in an extended temperature range below the characteristic temperature T * * (T * * < T * ; T * is the PG temperature): (i) the resistivity per CuO 2 sheet exhibits a universal, quadratic temperature dependence, and is inversely proportional to the doped carrier density p, ρ ∝ T 2 /p [15]; (ii) Kohler's rule for the magnetoresistvity, the characteristic of a conventional metal with a single relaxation rate, is obeyed, with a Fermi-liquid scattering rate, 1/τ ∝ T 2 [16]; (iii) the optical scattering rate exhibits the quadratic frequency dependence and the temperature-frequency scaling expected for a Fermi liquid [17]. In this part of the phase diagram, the Hall coefficient is known to be approximately independent of temperature and to take on a value that corresponds to p, R H ∝ 1/p [18].…”