As scientists form inter-layer quasiparticle pairs, we see faster, less energy-consuming devices

Researchers at the Australian National University (ANU) have discovered a way to create interlayer exciton pairs using bilayer semiconductor technology, paving the way for faster devices with less energy consumption.

This research could lay the foundation for a new generation of smartphones and computers, as well as next-generation technologies needed for high-speed computing, information processing, and data communication.

Professor Yuerui (Larry) Lu, principal investigator at the ARC Center of Excellence for Quantum Computing and Communications Technologies, said at ANU: news release That interlayer exciton pair was predicted by theory decades ago. But this is the first time it’s been observed in an experiment, he said.

first author of paper Announcing the discovery, Lu said the new semiconductor structure is incredibly small, lightweight, versatile, and invisible to the naked eye. It has promising applications in both the emerging space sector and quantum light sources.

Epoch Times photo
Lu said that interlayer exciton pairs were predicted by theory decades ago, but this is the first time they have been observed experimentally. (Yuerui (Larry) Lou/ANU)

Technology structure and mechanism

The technology was developed by sandwiching together two bendable single-layer semiconductors.

“The bilayer structure is made of two different semiconductors (two different materials),” Lu said in an email to The Epoch Times.

“In our case, the top layer is tungsten disulfide (WS2) and the bottom layer is tungsten diselenide (WSe2). Both of these two layers are atomically thin and have different physical properties. .”

A semiconductor bilayer creates an exciton pair between the two layers when the two layers absorb light. Excitons are quasiparticles formed by the attraction between negatively charged electrons and positively charged holes, and are created when electrons are expelled by the absorption of light.

“When a semiconductor absorbs light, electrons (negatively charged) are displaced (or excited) from their original places, leaving behind ‘holes’ (positively charged). “

Lu said that excited electrons and positively charged holes can combine through attractive interactions to form excitons.

“In our two-layer structure, the excited electrons are located in the top WS2 layer and the ‘holes’ are located in the bottom WSe2 layer. This is determined by the physical properties of these two semiconductors. “

He said that electrons in the top layer and “holes” in the bottom layer can form interlayer excitons (excitons that exist in two layers).

Exciton drive by voltage

Electric current can be thought of as the flow of electrons.In a circuit, electron flow is driven by Voltage— electrical pressure caused by a potential difference between terminals. For example, a chemical reaction inside a battery causes electrons to move to one side and no charge on the other side, creating a potential difference.

The current charges up over time, but Lu’s findings suggest that semiconductors form quasiparticles with net zero charge, The question can arise of how current flows in a circuit and produces electricity.

Lu says that because negatively charged electrons and positively charged “holes” reside in two different layers, voltages can be used throughout the circuit to drive the movement of inter-layer excitons. increase.

Electrons form attractive interactions with positively charged ‘holes’ in the bottom layer, but are still negatively charged in the top layer because there are no ‘holes’ in the top layer material. Therefore, when driven by a voltage, electrons move through the conductive material, thus allowing them to pass through the top layer of the transistor.

The bottom and top layers are connected by a conductor, and as electrons flow into this bottom layer they are able to fill the spaces of positively charged “holes”. Electrons flow through the bottom layer by moving to positively charged holes, are ejected from the layer when excited by light absorption, and flow into the rest of the circuit.

Epoch Times photo
The semiconductor is seen on the circuit board that powers the Samsung video camera at the Samsung Mobile Media and Analyst Event in San Jose, Calif., March 23, 2011. (Justin Sullivan/Getty Images)

Next step to new generation technology

The discovery also has the potential to help researchers achieve superfluidity. This is a state in which a collection of excitons condense into a superfluid so that current can flow without resistance and therefore without loss of kinetic energy.

PhD researcher Xueqian Sun, lead author of the paper, says superfluidity is best imagined as a “superhighway” in which excitons can travel at very high speeds, like cars on a highway. says.

“The current generation of semiconductor technology used in smartphones and laptops limits the speed at which excitons can travel, preventing them from reaching their full potential,” said Sun. .

“A good way to visualize this is to think of a car from bumper to bumper on a busy highway. It applies.”

Professor Lou said superfluidity is difficult to achieve with current semiconductor technology, and excitons can be scattered by many other particles.

“In conventional bulk III-V semiconductors, the binding energies of excitons are very low (just a few meV), and these excitons can only survive at very low temperatures.”

“New atomically thin semiconductor structures can host excitons with very high binding energies, which allows them to survive at very high temperatures (such as room temperature),” he says. Told.

“Interactions between interlayer excitons in the new semiconductor structure are also greatly enhanced and will help achieve superfluidity.”

Professor Lou said the next goal is to establish a superhighway that works at room temperature. This is because it is essential for integrating this semiconductor structure into smart devices.

“I honestly don’t know what to do at this point,” he said. “We need to discuss this with physicists and potentially work with them.”

Lily Kelly


Lily Kelly is an Australia-based reporter for The Epoch Times covering social issues, renewable energy, the environment, health and science.