Non-monotonic pseudo-gap in high-Tc cuprates

TL;DR

This paper reveals that the pseudo-gap in high-Tc cuprates exhibits a non-monotonic temperature dependence, challenging existing theories and suggesting a universal phenomenon in 2D metals related to charge ordering and electronic instabilities.

Contribution

It demonstrates the non-monotonic behavior of the pseudo-gap and draws parallels with charge ordering in transition-metal dichalcogenides, indicating a broader phenomenon in 2D metals.

Findings

Pseudo-gap shows non-monotonic temperature dependence.

Spectral similarities between cuprates and dichalcogenides.

Pseudo-gap may be a general feature of 2D metallic systems.

Abstract

The mechanism of high temperature superconductivity is not resolved for so long because the normal state of cuprates is not yet understood. Here we show that the normal state pseudo-gap exhibits an unexpected non-monotonic temperature dependence, which rules out the possibility to describe it by a single mechanism such as superconducting phase fluctuations. Moreover, this behaviour, being remarkably similar to the behaviour of the charge ordering gap in the transition-metal dichalcogenides, completes the correspondence between these two classes of compounds: the cuprates in the PG state and the dichalcogenides in the incommensurate charge ordering state reveal virtually identical spectra of one-particle excitations as function of energy, momentum and temperature. These results suggest that the normal state pseudo-gap, which was considered to be very peculiar to cuprates, seems to be a general complex phenomenon for 2D metals. This may not only help to clarify the normal state electronic structure of 2D metals but also provide new insight into electronic properties of 2D solids where the metal-insulator and metal-superconductor transitions are considered on similar basis as instabilities of particle-hole and particle-particle interaction, respectively.