Researchers from the National University of Singapore (NUS) have unveiled a revolutionary design concept for next-generation carbon-based quantum materials, creating a tiny, butterfly-shaped magnetic nanographene containing highly correlated spins that shows significant potential for the development of quantum information technology.
Magnetic nanographene, a tiny structure made up of graphene molecules, exhibits extraordinary magnetic properties due to the behavior of specific electrons in the π-orbitals of carbon atoms. Unlike conventional magnetic materials made from heavy metals, where different types of electrons from the d- or f-orbitals are involved, carbon’s π-electrons play a unique role. By precisely planning the arrangement of these carbon atoms at the nanoscale, control over the behavior of these unique electrons can be achieved.
This makes nanographene very promising for making the essential components known as quantum bits, or qubits, that are needed to create extremely small magnets and develop quantum computers. High-quality qubits need to maintain their quantum states, known as coherence time, for long periods of time while operating quickly. Carbon-based materials are known to increase the coherence time of spin qubits due to two unique properties: weak spin-orbit coupling and ultrathin coupling that effectively prevents electron spin mismatch.
A team of researchers led by Associate Professor LU Jiong from the NUS Department of Chemistry and Institute of Functional Smart Materials, together with Professor Jishan WU, also from the NUS Department of Chemistry, and international collaborators, have developed a method to create a large fully fused magnetic design and butterfly-shaped nanographene. This unique structure consists of four rounded triangles resembling the wings of a butterfly; each of these wings contains an unpaired π-electron responsible for the observed magnetic properties. This achievement is due to the atomically precise design of the π-electron network in the nanostructured graphene.
Associate Professor Lu said: “Magnetic nanographene, a small molecule composed of concatenated benzene rings, holds great promise as a next-generation quantum material to host exciting quantum spins due to its chemical versatility and long spin coherence time. However, creating a large number of entangled spins in such systems is a difficult but important task for creating scalable and complex quantum networks.”
This significant achievement was the result of close collaboration between synthetic chemists, materials scientists and physicists, including Professor Pavel Jelinek and Dr. Libor Vey from the Czech Academy of Sciences in Prague.
The groundbreaking findings of the research were recently published in a scientific journal Nature Chemistry .
Next-generation magnetic nanographene with highly entangled spins
The magnetic properties of nanographene generally arise from the arrangement of its special electrons, known as π-electrons, or the strength of their interactions. However, it is difficult to get these properties to work together to produce multiple correlated spins. Additionally, nanographene exhibits a special magnetic order in which the spins are preferentially aligned in one direction (ferromagnetic) or in opposite directions (antiferromagnetic).
To overcome these problems, researchers developed a new type of magnetic nanographene: a butterfly-shaped nanographene made by combining four small triangles into a diamond about 3 nanometers in size at the center, which has both ferromagnetic and antiferromagnetic properties.
To make this butterfly nanographene, the researchers first developed a special precursor molecule using traditional solution chemistry. This precursor was then used for further surface synthesis, a new type of solid-phase chemical reaction performed in a vacuum. This approach allowed the researchers to precisely control the shape and structure of the nanographene at the atomic level.
One intriguing aspect of this nanographene butterfly is that it has four unpaired π-electrons, whose spins are mostly delocalized and entangled in the “wing” regions. The researchers measured the exotic magnetism of the butterfly nanographene using an ultracold scanning probe microscope with a nickelodeon tip as a spin sensor at the atomic scale. In addition, this new technique helps scientists directly probe the entangled spins to understand how nanographene magnetism works at the atomic scale. This breakthrough not only solves existing problems, but also opens up new opportunities for precise control of magnetic properties at the smallest scale, leading to exciting advances in quantum materials research.
“The insights gained from this research pave the way for the creation of next-generation organic quantum materials with designer quantum spin architectures. Looking ahead, our goal is to measure spin dynamics and coherence times at the single-molecule level and manipulate these entangled spins coherently. This is an important step toward achieving more powerful information processing and storage capabilities,” added Associate Professor Lu.
Source: Port Altele
