1. Fluctuating stripes at the onset of the pseudogap in the high-T c superconductor Bi 2 Sr 2 CaCu 2 O 8+  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 Mostly studied in La 2-x (Sr,Ba,Eu,Nd) x CuO 4 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) Related subjects: Density waves Nematic order (leading proposals for pseudogap)

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

5. Inhomogeneity in conductance 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) Gap map Local spectra STM spectra locally inhomogeneous at pseudogap energy Why? Local doping? As doping decreases, average gap increases and width of gap distribution also increases Intrinsic? “local gap” Interstitial oxygen Gap distribution

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: T 0 THz spectroscopy, microwave impedance: ~10K above Tc Inna: Can’t really study this with ARPES, trust THz spectroscopy Nernst: Bz 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 ]arXiv:1005.4789v2

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

8. Main results Q* Q7Q7 Nothing happens at T 0 (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 35K Thoughts/comments: Why is q7 PSD so small @ 22%? Other explanations for peak near 1/8: Another competing state Pseudogap getting more incoherent

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

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