< Previous28ARC CENTRE OF EXCELLENCE IN FUTURE LOW-ENERGY ELECTRONICS TECHNOLOGIESResearch assistant Shaun Johnstone and colleagues building next-generation Bose-Einstein condensate apparatus at Monash University; better optical access will allow precise manipulation of atoms within the condensateSWINBURNE’S NEW QUANTUM-GAS MICROSCOPE FACILITYSingle-atom manipulation with new shared facility Clouds of atoms pushed temporarily out of equilibrium provide crucial insights into fundamental physics in FLEET’s Research theme 3. A new quantum-gas microscope facility at Swinburne University of Technology will allow studies of ultra-cold atomic gases, giving researchers the ability to image and manipulate single atoms. The new microscope will be a critical resource for diverse FLEET experiments, ranging across multiple research institutes including Swinburne, Monash University and ANU.The facility’s ability to image single atoms will greatly facilitate studies of the non-equilibrium, many-body quantum systems that are key to FLEET’s Research theme 3.Fundamental discoveries made from observing the transition of states will inform FLEET’s search for electronic conduction without wasted dissipation of energy.The new apparatus will use clouds of dysprosium (Dy) atoms, the large magnetic moment of which allows for long-range dipolar interactions.CASE STUDY29FLEET 2017 ANNUAL REPORTFLEET 2017 ANNUAL REPORTThese long-range, dipolar interactions provide an entirely new regime of interactions with which to engineer topological states for dissipationless transport.The quantum-gas microscope will allow atom-by-atom synthesis of tailored many-body states with novel topological properties.The new facility represents a paradigm shift for experimental ultra-cold atomic physics in Australia, with complex and expensive experiments performed by multiple researchers from a number of different cooperating institutions.FLEET researchers have established collaborations with Prof Tilman Pfau (University of Stuttgart) and Prof Wolfgang Ketterle (MIT) to learn the new skills that will be required in working with ultracold dysprosium atomic gases.Funding was approved under Australian Research Council LIEF grant ARC LE180100142 (November 2017). Also see list of grants on (see p90).Wolfgang Ketterle (Nobel laureate, MIT) lectures at FLEET annual workshop30PROF XIAOLIN WANGLeader, Enabling technology AUniversity of Wollongong“FLEET has established an ambitious goal that makes us work together closely” Expertise: design/fabrication and electronic/spintronic/superconducting properties of novel electronic or spintronic systems such as topological insulators, high spin-polarised materials, superconductors, multi-ferroic materials, single crystals, thin films, nano-size particles/ribbons/rings/wiresResearch outputs: 350+ publications, 5500+ citations, h-index 36ENABLING TECHNOLOGY AENABLING TECHNOLOGY A: ATOMICALLY-THIN MATERIALSEach of FLEET’s three research themes is heavily enabled by the science of novel, atomically-thin, two-dimensional (2D) materials.These are materials that can be as thin as just one single layer of atoms in thickness, with resulting unusual and useful electronic properties.To provide these materials, FLEET will draw on extensive expertise in materials synthesis in Australia and internationally, from bulk crystals to thin films to atomically-thin layers.The most well-known atomically-thin material is graphene, a 2D sheet of carbon atoms that is an extraordinarily-good electrical conductor.FLEET uses other atomically-thin materials, with its scientists seeking materials possessing the necessary properties for topological and exciton superfluid states.IN 2018, FLEET WILL: >Continue investigation of un-doped and magnetic-doped topological insulatorcrystal fabrication, such as Fe-Bi2Te3 and Fe-Sb2Se3 >Search for a new magnetic system for quantum anomalous Hall effect usingdensity-functional theory (DFT) >Measure quantum transport in very thin Fe-Sb2Se3 crystals; a collaborationbetween FLEET’s University of Wollongong and UNSW teams >Develop magnetic doping to induce anomalous Hall effect or quantumanomalous Hall effect (QAHE) >Fabricate Weyl semimetals with and without magnetic doping >Continue scanning tunneling microscope (STM) study of atomically-thin antimonyon various substrates at very low temperature and high magnetic field >Study electronic structures of these novel materials using new ARPES facilityat the Australian Synchrotron.It’s exciting to see FLEET addressing the energy challenge of computation through fundamental research on novel materials and unconventional physical mechanisms. This could have profound scientific and industrial impact.An Chen FLEET Advisory Committee Executive Director, Nanoelectronics Research Initiative (IBM)31FLEET 2017 ANNUAL REPORTPI Qi-Kun Xue discussing Weyl metals with PhD student Wafa Afzal, FLEET annual workshopDEFINITIONSelectronic smoothness Free of electronic imperfectionsgraphene A single 2D layer of carbon atomsmolecular beam epitaxy (MBE) A method used to deposit thin films of single crystalsquantum anomalous Hall effect (QAHE) A magnetic version of the quantum spin Hall effect, in which conducting edges carry currents in only one direction, and are completely without resistancetopological Dirac semimetal (TDS) Topological material at the boundary between conventional insulators (which don’t conduct) and topological insulators (which conduct along their edges)van der Waals (vdW) material A material naturally made of 2D layers, which can be isolated individually or stacked with other materials to form new structuresWeyl semimetals Similar to a topological Dirac semimetal, but with unusual surface states that may lead to dissipationless conduction2017 HIGHLIGHTS >Manufacturing the topological material Na3Bi to be as‘electronically smooth’ as the highest-quality graphene-based alternative, while maintaining electron mobilityas high as that of graphene (see p32) >Depositing atomically-thin, 2D materials usinga new liquid-metal approach: a simple, but ground-breaking innovation described as a ‘once-in-a-decade’advance (see p33) >Studying thickness-dependent electronic structurein WTe2 thin films, and observing transition to 2Dbehaviour as the samples are made thinner >Introducing defect-introduced paramagnetism andweak localisation to 2D metal VSe2 for the first time >Tuning electronic structure in twin layers of stanineand graphene using strain and gas adsorption,allowing control of the resulting state – whethera fully metallic interface or semimetallic/semiconductor transition >Discovering a new family of synthetic magneticstructures through atomic-scale engineering of oxideinterfaces – a major advance for the custom design ofspin structures >University of Wollongong researchers visiting FLEETPartner Investigator Prof Qi-Kun Xue’s group atTsinghua University, China.32ARC CENTRE OF EXCELLENCE IN FUTURE LOW-ENERGY ELECTRONICS TECHNOLOGIESELECTRONICALLY-SMOOTH ‘3D GRAPHENE’Topological material matches best graphene alternative for electronic smoothnessA new topological material provides the same remarkable electronic properties as graphene, without that material’s major drawback, electronic ‘messiness’.The 2D ‘wonder material’ graphene has theoretical electron speeds 100 times faster than silicon.But graphene’s 2D nature means it is far too flimsy to use on its own, and must be laid upon a solid substrate. And because graphene is atomically thin, electronic imperfections in the substrate are close enough to cause electronic imperfections in the graphene.Those imperfections are bad enough to severely restrict graphene’s electronic operation. In practice, this means graphene-based devices must be painstakingly constructed with a graphene sheet laid upon a substrate material that minimises such electronic disorder. Hexagonal boron nitride (h-BN) is commonly used for this purpose.But last year, FLEET researchers at Monash University found that the topological material Na3Bi can be as ‘electronically smooth’ as the highest-quality graphene-based alternative, while maintaining graphene’s high electron mobility.“This is the first time a 3D Dirac material has been measured in this way, so it’s particularly exciting to have CASE STUDYfound such a high degree of electronic smoothness,” says co-author and FLEET PhD student James Collins.The discovery will be critical for advancement of the study of this new topological material. It could have wide applications in electronics and potentially open other fields of research.With electronic smoothness of Na3Bi now demonstrated, an array of new research possibilities open up. There have been many studies into the relativistic (high mobility) flow of electrons in graphene since it was discovered in 2004. With this latest study, similar studies into Na3Bi can be expected.Na3Bi offers a number of interesting advantages over graphene.As well as avoiding the difficult construction methods involved in twin-layer graphene/h-BN devices, Na3Bi can be grown on a millimetre scale or larger. Currently, production of effective graphene/h-BN sheets is limited to only a few micrometres across.Another significant advantage is the potential to use Na3Bi as the conducting channel in a new generation of transistors – one built upon the science of topological insulators.“Electronic devices exploiting topological properties have much less power consumption than regular devices,” explains FLEET Associate Investigator A/Prof Shaffique Adam, who led the theoretical component of the study at the National University of Singapore.The study was published in Science Advances in December 2017, Vol. 3, no. 12 (see publication 7, p84).COLLABORATING FLEET PERSONNEL >Associate Investigator Mark Edmonds(Monash University) >PhD student James Collins (Monash University) >Associate Investigator Shaffique Adam (Yale-NUS) >CI Michael Fuhrer (Monash University)It’s exciting to be at the forefront of research into new materials that could change the face of electronics. It’s fast-paced and always changing – you have to be able to adapt and come up with new research directions quickly.Dr Mark Edmonds, Monash University FLEET Associate Investigator and study co-authorMark Edmonds closely monitoring Na3Bi growth, one atomic layer at a time33FLEET 2017 ANNUAL REPORTMetal droplets of gallium oxide (photo RMIT University)CASE STUDYLIQUID-METAL SOLUTION TO 2D MATERIAL DEPOSITION Once in a decade advance in 2D materialsFLEET’s development of new ultra-low dissipation electronic pathways is enabled by the new science of atomically-thin, two-dimensional (2D) materials.Large-scale deposition of such 2D materials is a key challenge for FLEET’s Enabling technology A.In 2017, a RMIT-led study found ground-shifting success with a new technique that will open new doors across the range of 2D semiconductors. The discovery has been described as a ‘once in a decade’ advance. The new technique introduces room-temperature liquid metals (gallium-based) as a successful reaction environment for the synthesis of desirable, atomically-thin oxides that were unattainable using prior methods. It can produce large-scale 2D materials across the periodic table.It’s a process so cheap and simple that it could be done on a kitchen stove by a non-scientist.“I could give these instructions to my mum, and she would be able to do this at home,” says new FLEET Associate Investigator Dr Torben Daeneke.The discovery brings previously-unattainable thin-oxide materials into everyday reach, with profound implications for future technologies.The simplicity of the method is extremely appealing: it does not require expensive equipment, is fully saleable, does not require vacuum technology and is extremely fast. This use of room-temperature liquid metals as solvents for creating 2D materials is completely novel, providing a brand-new pathway towards low-dimensional materials. In 2018, materials produced using the new technique will be further characterised to test their suitability for dissipationless electronics. Theoretical predictions will be used to identify further target materials for the liquid-gallium technique.The RMIT researchers also collaborated with colleagues at the Queensland University of Technology and University of California, Los Angeles (UCLA).COLLABORATING FLEET PERSONNEL >PhD student Ali Zavabeti (RMIT University) >Associate Investigator Jian-zhen Ou (RMIT University) >Research Fellow Ben Carey (RMIT University) >Honours student Rebecca Orrell-Trigg(RMIT University) >CI Kourosh Kalantar-Zadeh (RMIT University) >Associate Investigator Torben Daeneke(RMIT University)The study was published in Science in October 2017, Vol. 358, Issue 6361 (see publication 27, p84).A/PROF LAN WANGLeader, Enabling technology BRMIT University“Realising room-temperature quantum anomalous Hall effect could carry really significant benefits for humanity.”Expertise: Low-temperature and high-magnetic field electron and spin transport; topological insulators; magnetic materials; spintronic and magneto-electronic devices; device fabrication; growth of single crystals, thin films and nano-structures.Research outputs: 90+ papers, 2400+ citations, h-index 2634ENABLING TECHNOLOGY BENABLING TECHNOLOGY B: NANO-DEVICE FABRICATIONFLEET’s research sits at the very boundary of what is possible in condensed-matter physics. At the nano scale, nanofabrication of functioning devices will be key to the Centre’s success.Specialised techniques are needed to integrate novel atomically-thin, two-dimensional (2D) materials into high-quality, high-performance nano-devices.For example, atomically-thin topological insulators will need to be integrated with electrical gates to realise topological transistors. And atomically-thin semiconductors must be integrated with optical cavities to realise exciton–polariton condensate devices.Nano-device fabrication and characterisation links many of FLEET’s groups and nodes. Some groups bring expertise in device fabrication, while other groups are stronger in device characterisation. This teamwork is fundamental to modern science.FLEET brings together Australian strength in micro- and nanofabrication with world-leading expertise in van der Waals heterostructure fabrication to build the capacity for advanced atomically-thin device fabrication. Kourosh Kalantar-Zadeh in clean room gear, MicroNano Research Facility (RMIT University) 35FLEET 2017 ANNUAL REPORTIN 2018, FLEET WILL: >Fabricate vdW heterostructure devices for realisingquantum spin Hall effect (QSHE), quantumanomalous Hall effect (QAHE) and twin-layerexciton transistors >Realise various oxide heterostructure based devices.2017 HIGHLIGHTS >Establishing a dry transfer system for transferring andstacking van der Waals (vdW) heterostructures ina glove box, key to fabricating vdW heterostructuresfor FLEET’s Research themes 1 and 2 (see p18 and 22) >Developing vdW ferromagnetic metal with square-shaped loop, large coercivity and strong perpendicularmagnetic anisotropy, paving the way for spintronicdevices based on vdW ferromagnetic heterostructures >Establishing a focused ion beam (FIB) system fordevice fabrication that allows cutting and etchingnanostructures to custom shapes essential forelectronic and photonic devices.DEFINITIONSferromagnetic materials Material that can be magnetisedfocused ion beam (FIB) A microscope that uses a tight beam of ions to study nanoscale structures, and can also deposit or remove materials to form new structuresglove box Sealed container allowing manipulation within a controlled atmosphere via glovesheterostructure A structure in which two dissimilar materials are brought together at a controlled interfaceparamagnetic materials Materials that are attracted to magnetic fields and ferromagnets, but which are not magnetisedquantum spin Hall effect (QSHE) The spin-orbit interaction driven effect that gives a non-magnetic material conducting edges, which can carry current without resistance, as long as no magnetic disorder is presentquantum anomalous Hall effect (QAHE) A magnetic version of the QSHE (above), in which conducting edges carry currents in only one direction, and are completely without resistancevan der Waals (vdW) materials A material naturally made of 2D layers, held together by weak van der Waals forcesvan der Waals (vdW) heterostructure A structure made by stacking layers of different van der Waals materialsFLEET opens doors to new connections, new capabilities and new ideas that will help drive the quality and impact of my research.Dr Jeff Davis, Swinburne University of Technology FLEET Chief Investigator36ARC CENTRE OF EXCELLENCE IN FUTURE LOW-ENERGY ELECTRONICS TECHNOLOGIESFLEET PhD student Fan Ji developed this micro-sized logo at UNSW. The FLEET logo is etched onto the two-dimensional interface between two materials in letters only a few thousandths of a millimetre high, using bias-assisted atomic force microscopy (AFM) lithography. At Monash University, FLEET affiliate Marina Castelli used the tip of a scanning tunneling microscope (STM) to manipulate individual iron atoms, creating a nano-scale logo comprising just 42 atoms.MICRO BRANDINGFLEET researchers taking an innovative, even ‘playful’, approach to their science have created a couple of unique and interesting branding displays for the Centre.Atomic force microscopy (AFM) lithography is used in FLEET’s UNSW labs to study and ‘mill’ materials at microscopic scales. Using the extremely sharp tip of the microscope, surface features can be manipulated: adding and subtracting material as required, at an incredibly precise scale. The dimensions of the UNSW lithographic brand are approx. 19 micrometres long by 7 micrometres high.At Monash University, the sharp tip of a scanning tunneling microscope can be used to manipulate individual iron atoms into place, on a silver substrate. This technique is used to understand the structure of specific nanostructures, and to study their electronic properties. The logo shown is 40 nanometres long by 25 nanometres high, or 42 individual atoms.The slightly brighter atom in the middle of the 2nd ‘E’, is actually an accident: a small ‘tip crash’ of the instrument: “I was trying to push two iron atoms next to each other... luckily it did not destroy the other letters!” says Marina, who works with FLEET’s Agustin Schiffrin. 37FLEET 2017 ANNUAL REPORTFLEET 2017 ANNUAL REPORTLan Wang and colleague in Class 100 clean room, MicroNano Research Facility (RMIT)CASE STUDYCUSTOM, NANOSCALE STRUCTURES ON DEMAND AT RMITNanostructure fabrication to support FLEET researchFLEET’s research to achieve zero-dissipation electrical current depends on the design of key nanoscale structures.In 2017, Research theme B leader Lan Wang, and PhD student Cheng Tan, developed a method to build such nanoscale structures, required to achieve zero-dissipation electrical current.These nanostructures, comprising two stacked, 2D semiconductors, are key to FLEET’s Research theme 1 (topological materials) and Research theme 2 (exciton superfluids).Bound together by van der Waals (vdW) forces, and comprising twin, disparate, atomically-thin layers, such structures are known as van der Waals heterostructures.The new system, developed at RMIT, will enable the fabrication of a range of van de Waal structures, customised to realise room-temperature quantum anomalous Hall effect in Research theme 1 and twin-layer exciton superfluids in Research theme 2.The ‘dry’ transfer system allows transfer and stacking of individual layers in an air-free ‘glove box’, so that air-sensitive materials can be used, and contaminants between the layers, such as water, are eliminated. The method developed at RMIT allows the construction of numerous heterostructures, such as: >Ferromagnetic material–topological insulator >Ferromagnetic material–anti-ferromagnetic material >Ferromagnetic material–ferroelectric material >Superconductor–topological insulator.The possibilities for custom design are endless.VdW heterostructure fabrication has never previously been performed in Australia.In 2018, FLEET’s RMIT team will collaborate with Centre colleagues at Monash University and UNSW to set up the required systems. Then it will be all systems go: fabricating all kinds of vdW devices for the FLEET team.COLLABORATING FLEET PERSONNEL >PhD student Cheng Tan (RMIT University) >CI Lan Wang (RMIT University)Next >