Charge Ordering in out-of-plane Boron Doped Reduced Graphene Oxide

TL;DR

This study demonstrates charge ordering in boron-doped reduced graphene oxide above 97.5 K, driven by out-of-plane phonon interactions and electron-phonon coupling, supported by simulations and various spectroscopic techniques.

Contribution

It reveals a novel charge-ordered state in boron-doped graphene oxide induced by out-of-plane vibrations and electron-phonon interactions, with detailed experimental and theoretical analysis.

Findings

Charge ordering observed above 97.5 K.

Out-of-plane boron groups enhance electron-phonon coupling.

Charge ordering is influenced by doping, strain, and electric field.

Abstract

Symmetry-breaking phase transitions analogous to superconductivity (SC), charge ordering (CO) etc. in metal-intercalated graphene are favorable resulting from modified electronic and phonon band structures. Strong carrier-lattice interaction evolved from the out-of-plane soft vibrations with accumulation of charges at the out-of-plane region, can set a favorable environment for CO in graphene system. Here, we employ boron-doped reduced graphene oxide (BG) to acquire charge-ordered state above a transition temperature, T1~97.5 K. Signatures of this state are identified using ab-initio simulations and low temperature electrical transport measurements. The out-of-plane boron groups play a crucial role in reinforcing the electron-phonon coupling (EPC) allowing an ordered-state transition. Temperature-dependent Raman spectroscopy further supports the emergence of ordering. Key characterization techniques (X-ray diffraction, Raman spectra etc.) are used to quantify the EPC interaction and associated factors like tensile strain, boundary defects, etc. affecting charge ordering with doping. Additionally, we find interesting electric field dependency on the CO in this non-metallic, light-atom-doped chemically derived graphene.