Electronic Structure of Electron Doped Superconductor Sm1.85Ce0.15CuO4: Quantitative Analysis Based on (p,p) Scattering ModelChang Young KimDept. of Physics, Yonsei U

Work done byARPES S. Park, H.S. Jin, C.S. Leem (Yonsei) Peter Armitage (Geneva) B.J. Kim (SNU) H. Koh, Eli Rotenberg (ALS) Donghui Lu (SSRL)

SampleHiroshi Eisaki (AIST)

OutlinePast workInterpretation in (p,p) scattering modelNew data and further understandingSummary

Angle Resolved Photoemission Spectroscopy (ARPES) Photoelectron kinetic energy is measured Emission angle of photo electron is measured Energy and emission angle are transformed into momentumAngle (Momentum) Resolved PESEDCs at different angles

Electron Doped HTSCPhase Diagram

Hole- vs Electron-doped (Structure)Cu2+Nd3+/Ce4+O2-O2-(Nd,Ce)2CuO4(La,Sr)2CuO4 Cu2+La3+/Sr2+O2-O2- (Apical)No apical oxygens!

ARPES on Electron Doped HTSCRecent ARPES work: N. P. Armitage, PRL 86, 1126 (2001); 87, 147003 (2001); 88, 257001 (2002). T. Sato, Science 291, 1517 (2001); H. Matsui PRL 94, 047005 (2005); H. Matsui PRL 95, 017003 (2005)8 year gap!

Fermi liquid?Pr2-xCexCuO4 thin film* For hole-doped: rab ~ T ~ T2 depending on dopingP. Fournier et. al.ARPES

Sign change in RHY. Dagan, PRL, 92, 167001 (2004)

Main Valence Band6420Binding Energy (eV)hv = 16.5 eV T = 10 KNd2-xCexCuO4Intensity (Arb. Unit)13750.60.40.20.0

Fermi Surface SuppressionN. P. Armitage, PRL, 87,147003 (2001)Binding energy(eV) FS suppression at the intersection of AF Billiouin Zone Boundary (AFBZ) with the underlying FS Coupling to a bosonic mode localized at Q=(p,p)? If it is due to low energy Q=(p,p) bosonic mode, suppression is expected to exist on at the Fermi energy.kxky

Doping DependenceN. P. Armitage, PRL 88, 257001 (2002).

Theory IAssuming Q=(p,p) scattering channelC. Kusko, PRB 66, 140513 (2002)TheoryExpt-t-t-U(x)

PHYSICAL REVIEW B 72, 054504 (2005)PHYSICAL REVIEW B 66, 140513(R) (2002)PHYSICAL REVIEW LETTERS 91,186407 (2003)PHYSICAL REVIEW LETTERS 93,147004 (2004)More Theories (Hubbard or t-J models) Many-body calculations produce similar results : FS reconstruction, shadow FS & band folding.

AF ordering is assumed

Effect of OrderingNew Bragg plane

With a static ordering.

FS (Fig 1).

Band structure along the blue arrow in Fig 1 (Fig 2).ordering - (p, p) scattering AFBZEF(p,0)(p,p)Fermi surfaceGQ=(p,p)Fig. 1Fig.2Band Structure

New Band Structure AFBZ2Vp,pEFEF2Vp,pReconstructed FS (Fig 1).No electronic states at the Fermi energy where FS intersects the AFBZ.

Band structure along the cut (a) in Fig 1 (Fig 2).

Band structure along the cut (b) in Fig 1 (along the AFBZ, Fig 3).* Constant energy split (2Vpp)

Q=(p,p)(a)(b)Fig. 1Fig. 2Fig. 3

Interpretation of Recent NCCO (x=0.13)H. Matsui, PRL, 94, 047005 (2005)Binding energy(eV)00.20.10.3 FS suppression and band splitting Assigned to AF spin correlation Difficult to understand band structures near (p.0) in the model No quantitative analysis.

Going to ALS Sample : SCCO (Tc=13K) Sample preparation : FZ in situ cleaving Analyzer: Scienta 100 Temperature : 40 K Total Energy Resolution: 40 meV Angular Resolution: 0.25O Photon energy : 85eV Pass energy : 20eV Manipulator: 6 axis motion, completely Motorized Automated data acquisitionALS BL7

Movie (Graphite)kykxEMK

New Results from Sm1.85Ce0.15CuO4-2-1001kx (-1)kyGG2~1 eV total dispersion

Violation of Luttinger Theorem? x=0.15 2*shaded/square=1.073 0.073 more than half filled which is less than the doping 2*(shaded+2*little square)/square=1.20 which is larger than 1.15

Two Component Interpretation?G(p,p)(p,0)(0,p)this exists only near (p,0)This never reaches EF near (p,0). Signature of AF fluctuation?

Other Possibilities?- unreduced- hn=85eV- reduced- hn=85eV- reducedhn=135eVFS suppression is a universal character of the electron doped HTSCs.

Fitting the Exp Data within the Model 2Vp,p= 0.2eVG(p,p)kxEky

FS reconstruction & FS volumeYellow dashed lines near the (p,0) points are reconstructed FS segments.Fig 2 illustrates measurements of the filling factor. Filling factor for the original FS is about 1.07, but filling factor within the (p,p) scattering model is about 1.13.We observe an energy gap of ~10 meV at (p/2,p/2). This will be discussed later.

2Fig. 2Fig. 1500400300200100EFBinding Energy (meV)`Intensity (arb. Units)(p,0.3p)(p/2,p/2)Fig. 3

High Resolution DataFaint shadow FS (red arrow in Fig 1)Also visible in the published data from NCCO (PRL 94, 047005).

E vs k plot along the white arrow in Fig 1, along the AFBZ.Splitting of ~200 meV, consistent with high photon energy data from ALSFig. 2Fig. 1(p/2,p/2)(p,0)

Band Folding and Gap at the (p,p) Crossing(p,p)(0,0)500400300200100EFBinding Energy (meV)`Intensity (arb. Units)(p,0.3p)(p/2,p/2)(p,p) cut.Kink-like feature at about 50 meV.Band foldingGap due to band foldingFig. 1Fig. 3

Problems with the model : band structure near (p,0)AFBZAFBZAFBZBand splitting energy decreases as we approach the original Brilliouin zone boundary.This was interpreted as anisotropic spin correlation gap in an earlier work (PRL94,047005).Band folding is not centered at the AFBZ contrary to what anisotropic spin correlation gap would predict. Therefore, anisotropic gap interpretation can not be right.Fig. 1Fig. 2

Interpretation of Recent NCCO (x=0.13)H. Matsui, PRL, 94, 047005 (2005)Binding energy(eV)00.20.10.3 FS suppression and band splitting : AF spin correlation Hard to understand band structures near (p.0)

Hall MeasurementsPr2-xCexCuO4Y. Dagan, PRL, 92,167001 (2004) Suggest quantum critical point at a critical doping near 0.165

SummaryComprehensive analysis based on (p,p) scattering model

Band splitting due to (p,p) scattering appears to be robust. Vpp = ~100 meV (no momentum dependent scattering needed)

Doping and temperature dependence should clarify the issue