HQ Team
August 21, 2023: Scientists at the University of Cambridge have used novel materials to replace old quantum technology, techniques, and have spun out a new electron molecular module unit that functions at room temperature.
The researchers have found a way to use particles of light as a ‘switch’ that can connect and control the spin of electrons, making them behave like tiny magnets that could be used for quantum applications, according to a university statement.
Spin is the angular up-down movement of the electrons. Using the up-down spin states of electrons, instead of the 0 and 1 in conventional computer logic, could transform the way in which computers process information.
Sensors based on quantum principles could vastly improve our abilities to measure and study the world around us.
Almost all types of quantum technology — based on the strange behaviour of particles at the subatomic level — involve spin.
Radicals
As the particles move, electrons usually form stable pairs, with one electron spin up and one spin down. However, making molecules with unpaired electrons, called radicals is possible.
Most radicals are very reactive. With careful design of the molecule, they can be made chemically stable.
The researchers designed modular molecular units connected by tiny ‘bridges’. Shining a light on these bridges allowed electrons on opposite ends of the structure to connect to each other by aligning their spin states.
Even after the bridge was removed, the electrons stayed connected through their aligned spins, the authors wrote in the journal Nature.
This control over quantum properties can normally only be achieved at ultra-low temperatures.
The Cambridge-led team was able to control the quantum behaviour of these materials at room temperature, which opened up a new world of potential quantum applications by reliable coupling spins to photons.
Organic semiconductors
Organic semiconductors are the current state-of-the-art for lighting and commercial displays, and they could be a more sustainable alternative to silicon for solar cells.
However, they have not yet been widely studied for quantum applications, such as quantum computing or quantum sensing.
Organic semiconductors have carbon and hydrogen as their basic constituents.
They are the most important class of materials in the conducting organic materials list with a wide range of applications in devices like organic field-effect transistors, organic light-emitting diode, and organic solar cells.
In the international collaboration effort, scientists took materials that were made in China, experiments were done in Cambridge, Oxford, and Germany, and theory work was done in Belgium and Spain.
Sebastian Gorgon is from Cambridge’s Cavendish Laboratory. Gorgon is a member of Professor Sir Richard Friend’s research group, where they have been studying radicals in organic semiconductors for light generation.
His team identified a stable and bright family of materials a few years ago. These materials can beat the best conventional light-emitting diodes for red light generation.
Unpaired spins
“These unpaired spins change the rules for what happens when a photon is absorbed and electrons are moved up to a higher energy level,” said first author Mr Gorgon.
Dr Emrys Evans from Swansea University, who co-led the research said, “using tricks developed by different fields was important.”
“The team has significant expertise from a number of areas in physics and chemistry, such as the spin properties of electrons and how to make organic semiconductors work in LEDs.
“This was critical for knowing how to prepare and study these molecules in the solid state, enabling our demonstration of quantum effects at room temperature.”
The researchers designed a new family of materials by first determining how they wanted the electron spins to behave.
Using this bottom-up approach, they were able to control the properties of the end material by using a building block method and changing the ‘bridges’ between different modules of the molecule.
These bridges were made of anthracene, a type of hydrocarbon.
More flexibility
“In these materials we’ve designed, absorbing a photon is like turning a switch on. The fact that we can start to control these quantum objects by reliably coupling spins at room temperature could open up far more flexibility in the world of quantum technologies. There’s a huge potential here to go in lots of new directions.”
“We’ve now taken the next big step and linked the optical and magnetic properties of radicals in an organic semiconductor,” said Mr Gorgon. “These new materials hold great promise for completely new applications since we’ve been able to remove the need for ultra-cold temperatures.”
Sir Richard Friend said that knowing what the electron spins were doing “let alone controlling them” was not straightforward, especially at room temperature.
“But if we can control the spins, we can build some interesting and useful quantum objects.”
“People have spent years trying to get spins to reliably talk to each other, but by starting instead with what we want the spins to do and then the chemists can design a molecule around that, we’ve been able to get the spins to align,” said Sir Friend.
“It’s like we’ve hit the Goldilocks zone where we can tune the spin coupling between the building blocks of extended molecules.”
The distance Earth orbits the Sun is just right for water to remain a liquid. This distance from the Sun is called the habitable zone, or the Goldilocks zone.
