Strong anisotropy of cuprate pseudogap correlations: implications for Fermi arcs and Fermi pockets

Mike Guidry; Yang Sun; Cheng-Li Wu

doi:10.1088/1367-2630/11/12/123023

New Journal of Physics

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New Journal of Physics Volume 11 December 2009 Create an alert RSS this journal

Mike Guidry et al 2009 New J. Phys. 11 123023 doi:10.1088/1367-2630/11/12/123023

Strong anisotropy of cuprate pseudogap correlations: implications for Fermi arcs and Fermi pockets

Mike Guidry¹, Yang Sun^2,4 and Cheng-Li Wu³

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Abstract References Cited By

A full Fermi surface exists in underdoped high-temperature superconductors if the temperature T lies above the pseudogap (PG) temperature T^*. Below T^* the Fermi surface is anomalous. Some experiments indicate that only arcs of Fermi surface survive. Others indicate that the Fermi surface is closed but consists of pockets with a small surface area. We show that generalizing the Bardeen–Cooper–Schrieffer theory of normal superconductivity to include d-wave pairs and antiferromagnetism on a two-dimensional lattice leads to a T^* having a pronounced k dependence because of strong anisotropy in the PG correlations. We discuss implications for gapping of the Fermi surface within the Fermi arc and Fermi pockets picture of underdoped cuprates, and propose that related phenomena arising from anisotropic PG correlations may also occur in underdoped iron arsenide superconductors.

GENERAL SCIENTIFIC SUMMARY
Introduction and background. A full Fermi surface exists for underdoped cuprate superconductors above the pseudogap temperature T^*. However, below T^* and above the superconducting transition temperature T_c the Fermi surface is anomalous. Various angle-resolved photoemission spectroscopy (ARPES) experiments give evidence for an arc-like Fermi surface in the pseudogap region, while quantum oscillation experiments provide evidence for small pockets of Fermi surface in this region. A vigorous debate has ensued over whether these claims arising from rather different experimental techniques are compatible with each other, and over the implications of these results for understanding the pseudgap state and the general structure of cuprate superconductors.

Main results. By generalizing the BCS theory for normal superconductors to include the effects of antiferromagnetism on an equal footing with the superconductivity within an SU(4) Lie algebra, we find that T^* has a pronounced momentum-space anisotropy. This leads to strong temperature-dependent and doping-dependent restrictions on regions of the Brillouin zone where ungapped Fermi surface can exist. If we assume as a starting point a full hole Fermi surface, we obtain a quantitative description of ARPES Fermi arc properties without any parameter adjustment (Figure). If instead we assume the Fermi surface to consist of the closed pockets suggested by quantum oscillation experiments, our results place strong constraints on the possible size and location of those pockets. We propose that the new iron arsenide superconductors may exhibit similar effects because they are also described by an SU(4) symmetry.

Wider implications. We propose that the essential physics being probed by both quantum oscillation and ARPES experiments is a fundamental anisotropy of the pseudogap correlations predicted in this paper. If this interpretation is correct, it provides important new insight into the nature of the pseudogap state.

Figure for general scientific summary
Figure. Fermi arc length versus temperature. Experimental arc length is displayed as a percentage of full Fermi surface length versus temperature in units of T^* for underdoped Bi2212 (data from Kanigel et al [11]); the two curves are our predictions for two different assumed shapes of the Fermi surface (insets). No parameters were adjusted to these data in either calculation.

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