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**Overdoped cuprates are anisotropic marginal Fermi liquids**

** Ross McKenzie**

condensedconcepts.blogspot.com

University of Queensland

Brisbane, Australia

Understanding the metallic state of the high-Tc cuprate superconductors remains a formidable theoretical challenge. I will discuss recent work [1,2] that shows even the overdoped region of the phase diagram cannot be described as a simple Fermi liquid. The metallic state exhibits properties similar to optimal doping [marginal Fermi liquid] and underdoping [anisotropic Fermi surface properties with cold spots around the nodes of the superconducting energy gap].

First, I will describe the theory needed to describe the dependence of interlayer magnetoresistance on the direction of the magnetic field [angle dependent magnetoresistance (ADMR)] in a wide range of materials. ADMR turns out to be sensitive to anisotropies around an intralayer Fermi surface. Consequently, it has been used to determine anisotropies in the Fermi surface, interlayer hopping, and quasi-particle scattering rate [3].

These ADMR results led us to propose a phenomenological model self-energy which is the sum of two terms with characteristic dependencies on temperature, frequency, location on the Fermi surface, and doping [1]. The first term is isotropic over the Fermi surface, independent of doping, and has the frequency and temperature dependence characteristic of a Fermi liquid. The second term is anisotropic over the Fermi surface (vanishing at the same points as the superconducting energy gap), strongly varies with doping (scaling roughly with Tc, the superconducting transition temperature), and has the frequency and temperature dependence characteristic of a marginal Fermi liquid. This self energy gives a quantitative description of a wide range of experimental results including specific heat, ARPES, dc conductivity, optical conductivity, interlayer magnetoresistance, and Hall effect [2].

[1] J. Kokalj and R.H. McKenzie, Phys. Rev. Lett. 107, 147001 (2011).

[2] J. Kokalj, R.H. McKenzie, and N.E. Hussey, Phys. Rev. B 86, 045132 (2012).

[3] M. Abdel-Jawad et al., Nature Physics 2, 821 (2006).