Critical role of the sign structure in the doped Mott insulator: Superconductivity vs. Fermi liquid

TL;DR

This paper demonstrates that in doped Mott insulators, the intrinsic superconducting state can be transformed into a Fermi-liquid-like state by altering the sign structure, revealing a new pairing mechanism beyond traditional theories.

Contribution

It introduces a novel pairing paradigm in doped Mott insulators by showing the critical role of the sign structure in determining superconductivity versus Fermi liquid behavior.

Findings

Switching off the sign structure turns superconducting states into Fermi-liquid-like states.

Identifies a new pairing mechanism called 'Amperean-like pairing' with a stringlike force.

Adiabatic continuity links the pairing state to a strong anisotropic model limit.

Abstract

Mechanism of superconductivity (SC) in a purely interacting electron system has been one of the most challenging issues in condensed matter physics. In the BCS theory, the Landau's Fermi liquid is a normal state against which an SC instability occurs once an \emph{additional} pairing force is added. We show that in the doped Mott insulator an \emph{intrinsic} SC ground state (specifically a Luther-Emery state in a finite-doping two-leg $t$-$J$ ladder) can be directly turned into a Fermi-gas-like state by merely switching off the hidden statistical sign structure via two schemes. It points to a new pairing paradigm, %beyond the resonating-valence-bond scheme, which is an "Amperean-like pairing" with a "stringlike" pairing force as shown by an adiabatic continuity to a strong anisotropic limit of the model.