Quantum Oscillations in Underdoped YBCO

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Quantum Oscillations in Underdoped YBCO

• Brad Ramshaw
• Department of Physics and Astronomy
• University of British Columbia

UBC Superconductivity Group Doug Bonn Ruixing
Liang Walter Hardy James Day
Sherbrooke Louis Taillefer Nicolas
Doiron-Leyraud David LeBoeuf Mike
Sutherland David Hawthorn R.W. Hill, S.Y.
Li F. Ronning, M.A. Tanatar H. Zhang, J.
Paglione
CNRS Toulouse Cyril Proust David
Vignolles Cyril Jaudet, Alain Audouard, Julien
Levallois, B. Vignolle, M. Nardone, A. Zitouni
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YBCO

• Bilayer compound
• Degenerate energy levels from the two CuO2
  planes.
• Chains responsible for doping
• Keeps the disorder inherent to doping away from
  the action in the copper oxygen planes.
• Stoichiometric cations
• Orthorhombic
• a ? b

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LDA Band Structure for YBCO
I.S. Elfimov et al. PRB 060504(R) 2008
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ARPES on YBCO

• Hole Fermi surface
• Metalic behaviour
• Fermi Arcs
• Pseudogap region

Temperature (K)
0 50 100 15 200
250
0 .1 .2
.3
Hole Doping p
ARPES in YBa2Cu3O6x Hossain et al. Nature
Physics 4, 527-531 (2008).
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Hall Effect Measurements
LeBoeuf et al. Nature 450, 533-536 (2007)
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Quantum Oscillations
J.F Mercure. PhD Thesis (2008)
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Pulsed Field Resistance Measurements
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Oscillatory Amplitude
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Data Fits for Two Pockets
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Two Fermi Surfaces for YBCO 6.56
Re-scaled to enhance warping
Total area of Brillouin Zone 27.8 kT. 2. How
many of them?
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Two Fermi Surfaces for YBCO 6.50
YBCO 6.51
YBCO 6.56
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To-Scale Rendering of Pocket
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Where else could they come from?
Electron Pockets, different in size because YBCO
is orthorhombic
N. Harrison et al. arXiv 0903.4671v1
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Doping

• Doping depends on both oxygen content and chain
  length
• History matters!

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Why fits with 1 fermi surface dont work