# Apparent Reversal of Molecular Orbitals Reveals Entanglement

## TL;DR

This study uses scanning tunneling microscopy to observe how molecular orbital sequences change with charge state, revealing many-body entanglement effects that challenge single-particle models.

## Contribution

It demonstrates the reversal of molecular orbital order due to many-body entanglement in charged molecules, providing new insights into molecular electronic structure.

## Key findings

- Orbital sequence reverses with charge state on different substrates.
- Many-body theory explains the orbital reversal through entanglement.
- Experimental results challenge single-particle interpretations.

## Abstract

The frontier orbital sequence of individual dicyanovinyl-substituted oligothiophene molecules is studied by means of scanning tunneling microscopy. On NaCl/Cu(111) the molecules are neutral and the two lowest unoccupied molecular states are observed in the expected order of increasing energy. On NaCl/Cu(311), where the molecules are negatively charged, the sequence of two observed molecular orbitals is reversed, such that the one with one more nodal plane appears lower in energy. These experimental results, in open contradiction with a single-particle interpretation, are explained by a many-body theory predicting a strongly entangled doubly charged ground state.