Research theme 1

FLEET’s topological materials researchers (Research theme 1) showed that a topological quantum field-effect transistor (TQFET) can in principle switch at voltages smaller than predicted by the long-standing theoretical limit termed ‘Boltzmann’s tyranny’.

This places the TQFET as one of less than a handful of device concepts that can achieve low-voltage switching while using electronic charge as the carrier of information. A patent application has been lodged on the basis of the results. Research theme 1 has also made significant advances in understanding magnetic topological insulators, measuring for the first time the magnetism-induced topological bandgap in MnBi₂Te₄. Additionally the team had major input into the 2020 edition of the Internationl Roadmap for Devices and Systems, the semiconductor industry’s roadmap for future technologies, with the addition of the topological quantum field-effect transistor as a concept for ‘beyond CMOS’ devices.

Research theme 2

FLEET’s exciton superfluids collaboration demonstrated strong coupling of excitons in an atomically-thin semiconductor (WS₂) to light, forming exciton-polaritons at room temperature. This is a further step towards room-temperature condensation of exciton-polaritons in atomically-thin semiconductors. In a truly multidisciplinary collaboration involving researchers at ANU, Monash University and RMIT University, FLEET researchers solved a long-standing problem in the field of atomically-thin materials – using liquid-metal synthesis (previously developed in FLEET) to produce an atomically-thin, large-area, chemically-inert glass coating that encapsulated and protected atomically-thin semiconductor layers while preserving their excellent optical properties. This process is a key step in fabricating the stacks of atomically-thin semiconductor layers necessary to achieve exciton-polariton condensation.

Research theme 3

FLEET’s light-transformed materials team (Research theme 3) brought online at Monash University a new facility for ultra-fast spectroscopy of 2D materials. This facility will allow researchers to modify materials’ properties dynamically using an optical or infrared ‘pump’ light pulse of femtosecond duration, and to interrogate the resulting real-time femtosecond changes to materials’ properties using terahertz probe pulses. Theme 3 researchers also demonstrated femtosecond-timescale control of the bandstructure of atomically-thin semiconductors WS₂ and MoS₂. Theme 3 gained a better understanding of interactions in dynamical systems, developing the theory for quantum impurities and experimental techniques to probe sound propagation in Fermi gases.

Enabling technology A

FLEET’s materials researchers (Enabling technology A) synthesised high-quality crystals of 3D topological insulators and magnetic topological insulators showing topological properties up to 50 degrees Kelvin. These crystals are now being used across FLEET to fabricate topological devices. Theme A researchers discovered high thermopower in a topological insulator/nanoparticle composite. High-thermopower materials are promising for harvesting energy from waste heat, and a patent application was filed for the new material.

Enabling technology B

FLEET’s nano-device fabrication team (Enabling technology B) demonstrated a novel way to control the ferromagnetic coupling in the van der Waals ferromagnet Fe₃GeTe₂ by using an electrochemical ‘gate’ to inject protons in between the layers of the material. The liquid-metal technique for deposition of ultra-thin material layers (developed previously in FLEET) was expanded to piezoelectrics and carbon-based materials. Ferroelectric oxide hetero-structures were engineered to exhibit a novel negative differential resistance behaviour, also the subject of a patent application.