Complex Triplons: Development of Synthetic Quantum Magnets Using Entangled Electron-Based Quasiparticles

An artistic representation shows the magnetic excitations in cobalt-phthalocyanine molecules, wherein entangled electrons evolve into triplons. Credit: Jose Lado/Aalto University

A research team has identified a quantum entanglement wave through real-space measurements for the first time.

Triplons are intricate and elusive phenomena. They are exceptionally hard to detect experimentally, and when they are observed, it is typically in macroscopic materials, where the measurements represent an average over the entire sample.

This is where specially crafted quantum materials come into play, providing unparalleled benefits, according to Academy Research Fellow Robert Drost, the lead author of an article released on August 22 in Physical Review Letters. These specially crafted materials permit scientists to create occurrences that don’t exist in natural compounds, thus facilitating the emergence of unfamiliar quantum excitations.

“These substances are highly intricate. They present thrilling physics, yet the most unusual ones are also hard to discover and explore. Hence, we’re adopting an alternate method by constructing a synthetic substance utilizing individual elements,” explains Professor Peter Liljeroth, the leader of the Atomic Scale physics research group at Aalto University.

Quantum Material’s Electron Interactions

Quantum materials are controlled by the interplay among electrons at the microscopic scale. This leads to uncommon occurrences such as high-temperature superconductivity or intricate magnetic conditions, and quantum correlations result in novel electronic states.

In instances with two electrons, there are two entangled forms known as singlet and triplet states. Energizing the electron system might transition it from the singlet to the triplet state. Sometimes, this excitation can travel through a substance in an entanglement wave referred to as a triplon. Such excitations are not found in conventional magnetic substances, and their measurement has been a persistent issue in quantum materials.

Triplon Investigations

In recent research, small organic molecules were employed by the team to construct a synthetic quantum material with atypical magnetic characteristics, utilizing cobalt-phthalocyanine molecules, each containing two frontier electrons.

“Through the utilization of straightforward molecular components, we can construct and explore this multifaceted quantum magnet in an unprecedented manner, exposing phenomena absent in its isolated segments,” states Drost. “While magnetic excitations in lone atoms have been detected using scanning tunneling spectroscopy previously, propagating triplons have never been achieved.”

“We exploit these molecules to cluster electrons, compress them into confined spaces, and compel them to interact,” Drost adds. “Viewing such a molecule externally, we witness the collective physics of the electrons. As our basic unit now includes two electrons instead of one, we encounter a distinct kind of physics.”

The researchers observed magnetic excitations initially in individual cobalt-phthalocyanine molecules and subsequently in more extensive structures like molecular chains and islands. By commencing with the elementary and progressing toward escalating complexity, they aim to comprehend emergent behavior in quantum materials. In this specific study, they were able to demonstrate that the singlet-triplet excitations of their building blocks can travel molecular networks as unusual magnetic quasiparticles called triplons.

“We prove that we can produce an unconventional quantum magnetic excitation in a fabricated substance. This approach reveals that we can logically create material platforms that broaden the horizons in quantum technologies,” asserts Assistant Professor Jose Lado, one of the co-authors of the study, who leads the Correlated Quantum Materials research group at Aalto University.

The researchers intend to widen their methodology to more intricate components to create other peculiar magnetic excitations and ordering in quantum materials. Logical design from elementary components will not only aid in grasping the intricate physics of correlated electron systems but also form novel platforms for tailor-made quantum materials.

Reference: “Real-Space Imaging of Triplon Excitations in Engineered Quantum Magnets” by Robert Drost, Shawulienu Kezilebieke, Jose L. Lado, and Peter Liljeroth, 22 August 2023, Physical Review Letters.
DOI: 10.1103/PhysRevLett.131.086701

Frequently Asked Questions (FAQs) about fokus keyword: triplons

More about fokus keyword: triplons

• Physical Review Letters
• Aalto University
• Correlated Quantum Materials research group at Aalto University