Ubiquitous power law behaviour in the self energy of Strange Metals*

The high temperature superconducting state in cuprates is born out of the strange metal phase, showing resistivity linear in temperature, contravening Fermi liquid theory for metals. Theoretical understanding of this phase is limited, despite decades of research. Recently, the Anti-de Sitter/Conformal Field Theory (AdS/CFT) approach has been proposed to hold the answer, something we set out to test.
ARPES experiments are able to determine the normal state electron lifetime (described by a self-energy) in a k-resolved manner. In a 2015 arXiv post (1), laser-ARPES data from BSCCO-2212 proposed that the E- and T-dependence of the self-energy are power-laws. This got the AdS/CFT community excited, as this behaviour comes out of their calculations.
We have carried out analogous ARPES experiments on clean, single-layer BSCO-2201 systems over a wider range of T and E, obtaining some of the highest quality data ever recorded on these materials. This work presents the accurately extracted self-energies vs. energy and temperature, and often made assumptions such as k-independent self-energies are discussed. (1) Reber et al, arXiv (2015)