Why T_c is too high when antiferromagnetism is underestimated? --- An understanding based on the phase string effect

TL;DR

This paper explains why the superconducting transition temperature T_c is overestimated when antiferromagnetic fluctuations are underestimated, highlighting the importance of the phase string effect in accurately describing AF correlations and phase coherence.

Contribution

It introduces a bosonic RVB framework incorporating the phase string effect to better account for AF fluctuations and their impact on T_c in doped Mott insulators.

Findings

Underestimating AF fluctuations leads to overestimated T_c.

Bosonic RVB captures AF correlations more accurately.

Phase string effect reduces T_c to realistic values.

Abstract

It is natural for a Mott antiferromagnetism in RVB description to become a superconductor in doped metallic regime. But the issue of superconducting transition temperature is highly nontrivial, as the AF fluctuations in the form of RVB pair-breaking are crucial in determining the phase coherence of the superconductivity. Underestimated AF fluctuations in a fermionic RVB state are the essential reason causing an overestimate of T_c in the same system. We point out that by starting with a {\it bosonic} RVB description where both the long-range and short-range AF correlations can be accurately described, the AF fluctuations can effectively reduce T_c to a reasonable value through the phase string effect, by controlling the phase coherence of the superconducting order parameter.