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Parker et al Nature 468 677 (2010) PowerPoint Presentation
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Parker et al Nature 468 677 (2010)

Parker et al Nature 468 677 (2010)

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Parker et al Nature 468 677 (2010)

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  1. Fluctuating stripes at the onset of the pseudogap in the high-Tc superconductor Bi2Sr2CaCu2O8+d Parker et al Nature 468 677 (2010)

  2. outline • Concept reviews: • Stripes • FT-STS • Fluctuating SC • Inhomogeneity • Paper

  3. Stripes How does AF Mott insulator evolve upon hole doping? Spin-charge separation: perfect ordering possible at 1/8 doping Related subjects: Density waves Nematic order (leading proposals for pseudogap) Mostly studied in La2-x(Sr,Ba,Eu,Nd)xCuO4 Static stripes pinned by lattice distortions, suppress SC @ 1/8 doping (e.g. LBCO) 1/8=magic doping (others: 16%, 19%) Phys. Rev. Lett. 78, 338–341 (1997) Rev. Mod. Phys. 75 1201 (2003)

  4. Fourier transform STS and QPI Octet Model g(r,w=-10meV) g(q,w=-10meV) • Superconductor • Impurity induced interference • Study dispersion of interference peaks to infer momentum space properties • Quasiparticle interference (QPI) K. McElroy, et al. Nature 422 592 (2003) Y. Kohsaka, et al. Nature 454 1072 (2008)

  5. Inhomogeneity in conductance Local spectra Gap map • STM spectra locally inhomogeneous at pseudogap energy • Why? Local doping? • As doping decreases, average gap increases and width of gap distribution also increases • Intrinsic? Gap distribution Interstitial oxygen “local gap” Pushp et al, Science 324, 1689 (2009) Wise, et al. Nature Physics 5, 213 - 216 (2009) Alldredge et al Nature Physics 4, 319 - 326 (2008) McElroy et al. Science 309, 1048-1052 (2005)

  6. Fluctuating SC • SC fluctuations above Tc favorable in 2D systems • What temperature do SC fluctuations persist to? • Some ARPES people: T* • Nernst, torque magnetometry: T0 • THz spectroscopy, microwave impedance: ~10K above Tc • Inna: Can’t really study this with ARPES, trust THz spectroscopy Nernst: Ey Nernst: Phys. Rev. B 64, 224519 (2001 Diamagnetism: Phys. Rev. B 81, 054510 (2010) THz: Ann. Phys. 15 596 (2006) Microwave: arXiv:1005.4789v2 [cond-mat.supr-con] Bz

  7. Z-map and S-map Z-map: enhances QPI signatures • Suppresses QPI signatures • Enhances q associated with pseudogap • Phase information FT Real space • This translation/rotation symmetry breaking pattering is enhanced at pseudogap energy • Corresponds to Q* and Q** Y. Kohsaka, et al. Nature 454 1072 (2008)

  8. Main results • Nothing happens at T0 (roughly the Nernst line) (Topic for future discussion!) • Q* is indeed associated with pseudogap • Intensity of superconducting wavevector (q7) peaked near OP, intensity of PG wavevector peaked near 10% (~1/8) • Why associate Q* with stripes? • Intensity peaked near ‘magic doping’ • Wavevector inconsistent with antinode nesting, but consistent with half-filled stripe Q* Q7 • Thoughts/comments: • Why is q7 PSD so small @ 22%? • Other explanations for peak near 1/8: • Another competing state • Pseudogap getting more incoherent 35K

  9. Pseudogap incoherence ARPES, AN, our data p<10%: perhaps FT-STS signal comes primarily from ‘small gap’ regions? What else happens below 10%? Antinodal spectra become increasingly incoherent, AN QP disappears Wise, et al. Nature Physics 5, 213 - 216 (2009)

  10. Spatial correlation OP What came first, pseudogap or stripes? They say: Pseudogap nucleates stripes because pseudogap is associated with local spin correlations p>10%: large gap<-> strong Q* p<10%: large gap<-> weak Q* Also fits with decoherence argument