Origin of the Fermi arcs in cuprates: a dual role of quasiparticle and pair excitations

Abstract

ARPES mesurements in cuprates have given key information on the temperature and angle dependence of the gap (d-wave order parameter, Fermi arcs and pseudogap). We show that these features can be understood in terms of a Bose condensation of interacting pairons (preformed hole pairs which form in their local antiferromagnetic environment). Starting from the basic properties of the pairon wavefunction, we derive the corresponding k-space spectral function. The latter explains the variation of the ARPES spectra as a function of temperature and angle up to T * , the onset temperature of pairon formation. While Bose excitations dominate at the antinode, the fermion excitations dominate around the nodal direction, giving rise to the Fermi arcs at finite temperature. This dual role is the key feature distinguishing cuprate from conventional superconductivity.

How ‘pairons’ are revealed in the electronic specific heat of cuprates

“…It is close to the node that quasiparticle excitations from decaying pairons dominate. This is the Fermi-arc contribution included in our calculation, being directly proportional to T c /T * , as we have shown in [25]. In the underdoped regime, for T < T c T h pairon excitations dominate in entropy and the specific heat ( Fig.…”

“…Both parameters depend on a single energy scale, the antiferromagnetic exchange energy J [20] and one length scale ξ AF [23]. The pairon model hamiltonian allows to calculate the spectral function as well as the density of states in excellent agreement with the experimental tunneling spectra [24] as well as ARPES, as a function of temperature and doping [25].…”

Single origin of the nodal and antinodal gaps in cuprates

“…The latter display the characteristic Bogoliubov quasiparticle dispersion indicating preformed pairs [29,30]. In the pairon model, the Fermi arc is the result of fermion excitations, due to the composite fermion character of pairons, while the pseudogap is a manifestation of an incoherent state of excited pairons, absent in a conventional BCS superconductor [31].…”

“…For this purpose, we start from the expression of the hole pair wavefunction in relative coordinates. In our previous work [31], only first nearest neighbours were considered (red dots in Fig. 4):…”

“…9) then gives rise to additional terms. As described in a previous article [31], the pairon wavefunction can then be expressed as a superposition of Cooper pairs in k-space. Extending the calculation derived in [31], we obtain the gap function:…”