Hidden Charge 2e Boson: Experimental Consequences for Doped Mott Insulators

TL;DR

This paper proposes that a charge 2e bosonic field in doped Mott insulators explains many normal state properties of cuprates, predicting a new charge e excitation observable via electron energy loss spectroscopy.

Contribution

It introduces a novel charge 2e bosonic field in the low-energy theory of doped Mott insulators, linking it to various experimental phenomena and predicting a new charge e composite excitation.

Findings

Explains mid-infrared band and sum rule violation.

Accounts for pseudogap and electron spectrum bifurcation.

Predicts a sharp quasiparticle peak in the inverse dielectric function.

Abstract

We show here that many of the normal state properties of the cuprates can result from the new charge 2e bosonic field which we have recently (Phys. Rev. Lett. {\bf 99}, 46404 (2007) and Phys. Rev. B 77, 014512 (2008)) shown to exist in the exact low-energy theory of a doped Mott insulator. In particular, the 1) mid-infrared band including the non-vanishing of the restricted f-sum rule in the Mott insulator, 2) the $T^2$ contribution to the thermal conductivity, 3) the pseudogap, 4) the bifurcation of the electron spectrum below the chemical potential as recently seen in angle-resolved photoemission, 5) insulating behaviour away from half-filling, 6) the high and low-energy kinks in the electron dispersion and 7) T-linear resistivity all derive from the charge 2e bosonic field. We also calculate the inverse dielectric function and show that it possesses a sharp quasiparticle peak and a broad particle-hole continuum. The sharp peak is mediated by a new charge e composite excitation formed from the binding of a charge 2e boson and a hole and represents a distinctly new prediction of this theory. It is this feature that is responsible for dynamical part of the spectral weight transferred across the Mott gap. We propose that electron energy loss spectroscopy at finite momentum and frequency can be used to probe the existence of such a sharp feature.