1 research outputs found
Energy gaps in high-transition-temperature cuprate superconductors
The spectral energy gap is an important signature that defines states of
quantum matter: insulators, density waves, and superconductors have very
different gap structures. The momentum resolved nature of angle-resolved
photoemission spectroscopy (ARPES) makes it a powerful tool to characterize
spectral gaps. ARPES has been instrumental in establishing the anisotropic
d-wave structure of the superconducting gap in high-transition temperature (Tc)
cuprates, which is different from the conventional isotropic s-wave
superconducting gap. Shortly afterwards, ARPES demonstrated that an anomalous
gap above Tc, often termed the pseudogap, follows a similar anisotropy. The
nature of this poorly understood pseudogap and its relationship with
superconductivity has since become the focal point of research in the field. To
address this issue, the momentum, temperature, doping, and materials dependence
of spectral gaps have been extensively examined with significantly improved
instrumentation and carefully matched experiments in recent years. This article
overviews the current understanding and unresolved issues of the basic
phenomenology of gap hierarchy. We show how ARPES has been sensitive to phase
transitions, has distinguished between orders having distinct broken electronic
symmetries, and has uncovered rich momentum and temperature dependent
fingerprints reflecting an intertwined & competing relationship between the
ordered states and superconductivity that results in multiple
phenomenologically-distinct ground states inside the superconducting dome.
These results provide us with microscopic insights into the cuprate phase
diagram.Comment: A review article for ARPES studies on high-Tc cuprates. 6 figure