Destruction of the Fermi Surface in Underdoped High Tc Superconductors

TL;DR

This paper investigates how the Fermi surface in underdoped high Tc superconductors breaks up into disconnected arcs with increasing temperature, revealing a novel phenomenon without long-range order and linking pseudogap and superconducting gaps.

Contribution

It presents the first ARPES measurements showing the temperature-dependent destruction of the Fermi surface in underdoped Bi2212, uncovering unprecedented behavior in the pseudogap regime.

Findings

Fermi surface breaks into disconnected arcs above Tc

Different k points become gapped at different temperatures

Fermi arcs shrink and collapse to point nodes below Tc

Abstract

The Fermi surface is a central concept in the theory of metals. Even though the optimally doped high temperature superconductors exhibit an anomalous normal state, angle resolved photoemission spectroscopy (ARPES) has revealed a large Fermi surface despite the absence of well-defined quasiparticles and the necessity of working at finite temperatures. However, the even more unusual behavior in the underdoped high temperature superconductors, which show a pseudogap above Tc, requires us to carefully re-examine this concept. Here, we present the first results on how the Fermi surface is destroyed as a function of temperature in underdoped Bi2212 using ARPES. We find the remarkable effect that different k points become gapped at different temperatures. This leads to a break up of the Fermi surface at a temperature T* into disconnected Fermi arcs which shrink with decreasing T, eventually collapsing to the point nodes of the dx2-y2 superconducting ground state below Tc. This novel behavior, where the Fermi surface does not form a continuous contour in momentum space, is unprecedented in that it occurs in the absence of long range order. Moreover, although the d-wave superconducting gap below Tc smoothly evolves into the pseudogap above Tc, the gaps at different k points are not related to one another above Tc the same way as they are below, implying an intimate, but non-trivial relation, between the two.