Fluctuating stripes at the onset of the pseudogap in the high-Tc

superconductor Bi2Sr2CaCu2O8+

Parker et al

Nature 468 677 (2010)

outline

• Concept reviews:– Stripes– FT-STS– Fluctuating SC– Inhomogeneity

• Paper

StripesHow does AF Mott insulator evolve upon hole doping?

Spin-charge separation: perfect ordering possible at 1/8 doping

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)

Related subjects:

Density waves

Nematic order

(leading proposals for pseudogap)

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)

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

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:

Bz

xT Ey

||/ xyn TEe

Nernst: Phys. Rev. B 64, 224519 (2001Diamagnetism: Phys. Rev. B81, 054510 (2010)THz: Ann. Phys. 15 596 (2006)Microwave: arXiv:1005.4789v2 [cond-mat.supr-con]

Z-map and S-map

Z-map: enhances QPI signatures),(

),(),(

Vg

VgVZ

qq

q

0

0

0

0

|),(|

|),(|),( 0 V

V

V

V

dVVg

dVVgVS

q

qq

•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)

Main resultsQ*

Q7

•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

35K

Thoughts/comments:•Why is q7 PSD so small @ 22%?•Other explanations for peak near 1/8:

•Another competing state•Pseudogap getting more incoherent

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

Spatial correlation

OP

p>10%: large gap<-> strong Q*p<10%: large gap<-> 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