Tuning fulleride electronic structure and molecular ordering via variable layer index

TL;DR

This study demonstrates precise control over the electronic and structural properties of KxC60 fulleride films by manipulating layer index, revealing phase transitions and evolution of molecular ordering, which advances the design of molecular electronic devices.

Contribution

It introduces a method to tune fulleride properties via atomic layer control and doping, providing new insights into phase transitions and molecular ordering in ultra-thin films.

Findings

Observation of electronic and structural phase transitions with layer variation

Systematic evolution of electronic structure with layer index

Control of molecular ordering in ultra-thin fulleride films

Abstract

C60 fullerides are uniquely flexible molecular materials that exhibit a rich variety of behavior, including superconductivity and magnetism in bulk compounds, novel electronic and orientational phases in thin films, and quantum transport in a single-C60 transistor. The complexity of fulleride properties stems from the existence of many competing interactions, such as electron-electron correlations, electron-vibration coupling, and intermolecular hopping. The exact role of each interaction is controversial due to the difficulty of experimentally isolating the effects of a single interaction in the intricate fulleride materials. Here we report a unique level of control of the material properties of KxC60 ultra-thin films through well-controlled atomic layer indexing and accurate doping concentrations. Using STM techniques, we observe a series of electronic and structural phase transitions as the fullerides evolve from two-dimensional monolayers to quasi-threedimensional multilayers in the early stages of layer-by-layer growth. These results demonstrate the systematic evolution of fulleride electronic structure and molecular ordering with variable KxC60 film layer index, and shed new light on creating novel molecular structures and devices.