Navigating Fermi Arcs

SSRL Science Summary - November 2012

In solids, Fermi surfaces are the boundaries between occupied and unoccupied electron levels, as defined in momentum space. Their properties dictate that each Fermi surface should form a single unbroken loop. To the surprise of physicists, disconnected segments of the Fermi surface - Fermi arcs - were discovered in cuprate superconductors in 1998.

In a study recently published in Nature Physics, researchers from the University of Colorado have used angle-resolved photoemission spectroscopy (ARPES) at SSRL Beam Line 5-4 to determine these origin of Fermi arcs in the cuprates. With the help of the beamline's excellent energy resolution and a new, somewhat unorthodox method of analyzing the resulting spectrum, they determined the momentum and temperature dependencies of two important parameters: the superconducting gap magnitude, D, and the Cooper pair-breaking rate, G.

They were able to determine that D changes very little with temperature, even through TC, suggesting Cooper pairs continue to exist in the normal state, and that G is unconventionally large and strongly temperature-dependent, shifting weight from the peaks into the gap and effectively filling it. Essentially, Fermi arcs are a byproduct of an intense competition between pair-forming and pair-breaking processes, a foam of non-quasiparticle states that is a fascinating candidate to explain the non-Fermi liquid physics dominating the normal state of the cuprates.

 

Primary Citation

Reber, T. J. et al. The Origin and Non-quasiparticle Nature of Fermi Arcs in Bi₂Sr₂CaCu₂O₈+d. Nature Physics 8, 606-610 (2012)
[DOI: 10.1038/nphys2352]

Related Links

• Science Highlight – HTML  /  PDF

Contacts

Ted J. Reber and Daniel S. Dessau (University of Colorado)