1. Antiferromagnetic Fluctuations and Photoemission Spectra in E-Doped Cuprates
Bumsoo Kyung, Vasyl Hankevych, and André-Marie Tremblay
Département de Physique Université de Sherbrooke
III. Analytical approach
IV. Results: single-particle spectral properties
Outline
U=5.75, n=1.15
U=6.25, n=1.10
U=5.25, n=1.15
U=5.75, n=1.15
Motivations
Model
Analytical approach: TPSC
Results: single-particle spectral properties
Discussion and conclusions
U=6.25, n=1.15
U=6.25, n=1.10
I. Motivations:
Fermi surface plot in the first Brillouin zone
Hot spots in recent ARPES
Armitage et al. [PRL 87, (2001); 88, (2002)]
indicate importance of antiferromagnetic fluctuations
U=5.75, n=1.15
U=5.75, n=1.05
U=6.25, n=1.10
Antiferromagnetic x in neutrons
Single-particle spectral function along the Fermi surface
Reproduces experiment for 10% e-doping
Reproduces experiment for 15% e-doping
Scattering rates in the first Brillouin zone
U=6.25, n=1.10
U=5.75, n=1.15
T=1/40
T=1/40
T=1/10
Validation of TPSC
P.K.Mang et al., cond-mat/ ;
It satisfies the Mermin-Wagner theorem + Pauli principle.
Transition replaced by crossover temperature below which the magnetic correlation length grows exponentially.
Comparison of the charge and spin structure factors, spin susceptibility and double occupancy are in quantitative agreement with QMC.
Single-particle spectral function in energy-momentum plane: X=(0,p), G=(0,0), M=(p,p), H=(p/2,p/2)
Electron-doped cuprates might be better described by smaller Coulomb repulsion U than the bandwidth
theoretical and experimental evidence C.Kusko et al., PRB 66, (2002); B.Kyung et al., cond-mat/ ; D.Sénéchal et al., cond-mat/
n=0.90
U=6.25
(t’= -0.3, t’’=0.2)
n=0.85
This opens the door to weak- to intermediate-
coupling-based approaches which can also describe
well antiferromagnetic fluctuations.
Fermi surface plot for hole-doped system (qualitative only).
(p/2,p/2) region should be smaller.
These are more strongly coupled.
TPSC
Fermi surface plot for 17% electron-doped system from CPT by D.Sénéchal et al. [cond-mat/ ]
V. Discussion and conclusions
Comparisons with other approaches:
II. Model:
Tohyama et al. [PRB 64, (2001)] used exact diagonalization for t-t’-t’’-J model: small Fermi surface around (p,0).
Kusko et al. [PRB 66, (2002)] used SDW approximation for the Hubbard model: increasing spectral weight near (p/2,p/2) due to the crossing of the lower Hubbard band to the Fermi energy.
Kusunose et al. [cond-mat/ ] considered multiple exchange of transverse spin excitations in the mean-field SDW state: increasing spectral weight near (p/2,p/2) due to the strong admixture of the lower and upper quasihole states.
All these approaches are expected to work well only close to half-filling, while TPSC gives better description for less strongly correlated systems and large but finite correlation length (No antiferromagnetic order).
Calc.: Y.Vilk et al., PRB 49, (1994)
QMC: S.White et al., PRB 40, 506 (1989)
d = 2 Hubbard model, simplest model of interacting electrons. Here U > 0
n; T U t
TPSC
n Filling
T Temperature
Conclusions:
TPSC could reproduce hot spots for 15% electron-doped cuprates and a spread of the pseudogap with decreasing doping, observed in recent ARPES data. (See also B.Kyung et al., cond-mat/ ).
Features caused by finite range antiferromagnetic fluctuations peaked at (p,p).
Pseudogap occurs when x > xth (antiferromagnetic correlation length larger than single-particle thermal De Broglie wavelength.)
Experimental ARPES data are better described by a smaller U with increasing doping, supporting the recent proposal based on theoretical and experimental works.
TPSC could explain the qualitative difference of ARPES spectra between hole- and electron-doped cuprates: large spectral weight near (p/2,p/2) for hole-doped cuprates and near (p,0) for electron-doped cuprates. Real hole-doped systems are in strong-coupling regime.
TPSC could reproduce experimentaly observed x(T) for electron-doped cuprates near optimal doping.
Weak coupling:
U < 8t
t’= , t’’= +0.05,
T=1/40
Calc. + QMC: S.Moukouri et al., PRB 61, 7887 (2000)
Acknowledgments:
David Sénéchal