One of the most difficult problems in quantum materials is controlling the internal states of quantum systems. Although they have the same number of electrons, individual molecules can exhibit different quantum states at the most fundamental level. These states can have radically different characteristics because they are associated with different electron configurations.

Controlling the electrical structure of individual molecules could enable significant advances in both basic science and technology. However, controlling the internal states of molecules remains a challenge, and realistic, scalable strategies to overcome this have yet to be proposed.

Researchers from Aalto University and Jyväskylä University recently achieved an experimental breakthrough by showing that they can manipulate the quantum states of individual molecules using an electrically controlled substrate. Their research showed how a particular two-dimensional substance called SnTe provides the instrumental resources needed to regulate molecular states.

The researchers’ approach is based on a substrate’s ability to tune the internal state of molecules as a result of internal electric fields. This mechanism, known as ferroelectric molecular switching, allows researchers to control individual molecules simply by applying a voltage to the substrate. The tactic is based on SnTe’s significant external voltage tunability, which is the result of a special quantum phenomenon known as ferroelectricity.

Professor Shawulienu Kezilebieke from the University of Jyväskylä said: “Our results show how we can control individual molecules using electrically tunable two-dimensional materials. From a practical point of view, two-dimensional ferroelectric devices have played an important role, as the ultra-clean interface makes it possible to realize this strategy of quantum control. These experiments devised a strategy to engineer quantum states at the molecular level, opening up exciting possibilities in single-molecule artificial materials and electronics.”

Ph.D. researcher Mohammad Amini, the study’s first author, said: “In our experiments, we have shown how two-dimensional ferroelectricity enables us to realize electrically switchable quantum states. Controlling quantum states electrically is an important milestone in quantum materials, and here we have demonstrated a strategy to do this at the deepest level of individual molecules.”

Magazine reference:

  1. Mohammad Amini, Orlando J. Silveira et al. Control of molecular orbital ordering using a van der Waals monolayer ferroelectric. Advanced materials. DOI: 10.1002/adma.202206456