Temperature-dependent electronic ground state charge transfer in van der Waals heterostructures

TL;DR

This study reveals that temperature significantly influences charge transfer in van der Waals heterostructures, with charge transfer increasing threefold from cryogenic to room temperature, driven by electron-phonon and electronic couplings.

Contribution

It introduces the first experimental observation of temperature-dependent charge transfer in van der Waals heterostructures and provides a theoretical model explaining this behavior.

Findings

Charge transfer increases threefold from 7 K to room temperature.

Electron-phonon and electronic couplings are key factors in charge transfer.

A theoretical model explains the temperature dependence in multi-component heterostructures.

Abstract

Electronic charge rearrangement between components of a heterostructure is the fundamental principle to reach the electronic ground state. It is acknowledged that the density of states distribution of the components governs the amount of charge transfer, but a notable dependence on temperature has not yet been considered, particularly for weakly interacting systems. Here, we experimentally observe that the amount of ground state charge transfer in a van der Waals heterostructure formed by monolayer MoS2 sandwiched between graphite and a molecular electron acceptor layer increases by a factor of three when going from 7 K to room temperature. State-of-the-art electronic structure calculations of the full heterostructure that account for nuclear thermal fluctuations reveal intra-component electron-phonon coupling and inter-component electronic coupling as the key factors determining the amount of charge transfer. This conclusion is rationalized by a model applicable to multi-component van der Waals heterostructures.