Category Archive

Using ultrafast laser pulses we demonstrate adiabatic control of the bandstructure of monolayer WS2 through Floquet engineering. In other words the periodic electric field of the laser pulse dresses the Bloch bands of the semiconductors. Interactions between the dressed bands then cause energy shifts, avoided crossings and the potential to induce a topological phase transition. The use of coherent spectroscopy …

  In this talk I will present the case for using high-electric field, ultrashort femtosecond pulses of light to controllably switch the behaviour of topologically interesting systems such as the Dirac semimetal, graphene. I will also outline our research efforts in this space and why quasi-single cycle terahertz probe pulses provide a unique window into the dynamics and optical properties …

Intrinsic magnetic topological insulators offer the potential of low disorder and large magnetic bandgaps for robust magnetic topological phases operating at higher temperatures, enabling observation of phenomena such as the quantum anomalous Hall effect (QAHE) and axion insulator phases [1,2]. However, these observations occur at temperatures significantly lower than the Neel temperature of bulk MnBi2Te4, and measurement of the magnetic energy …

I will give an update on recent theoretical progress in understanding the nature of interactions in exciton-polariton systems. About the presenter CI A/Prof Meera Parish develops many-body theories that span electron-hole systems and ultracold atomic gases. In Research Theme 2, she is investigating the fundamental properties of exciton-polariton condensates, while in Research Theme 3, she is studying quantum systems out of …

Isolation of monolayer and few-layer graphene and other two-dimensional materials provides an opportunity to fabricate new types of heterostructures by stacking them layer by layer in a designed sequence [1]. Previous studies show that putting a graphene on a hexagonal boron nitride (hBN) substrate could form a Moiré pattern which generates a periodic potential and creates new Dirac points in …

Exciton-polaritons (polaritons herein) are bosonic quasiparticles with unique physical properties arising from strong coupling between excitons and confined photons. Since their first demonstration, exciton-polaritons became a convenient platform for studies of collective quantum effects such as Bose-Einstein condensation and superfluidity. To date, the most striking effects were cleanly demonstrated in GaAs- based microcavities due to the very low defect densities …

Electron transport in most solid state systems is dominated by extrinsic factors, such as sample geometry and scattering from impurities, and is essentially independent of the intrinsic properties of the electron system. An exception is the hydrodynamic regime, where Coulomb interactions transform the electron motion from independent particles to the collective motion of a viscous ‘electron fluid’. The fluid viscosity …

Intrinsic TIs are nonmagnetic or antiferromagnetic materials, possessing linear dispersed surface states with helical-textured spin configuration. With ferromagnetic ordering, a so-called massive Dirac state is achieved, in which the spin texture near Dirac gap is hedgehog like. Particularly, with fully spin polarization at Fermi surface, one can obtained the half-metallic TI, which should also exhibite the massive Dirac states, and …

Two-dimensional layered materials have been at the forefront of material research ever since the discovery of graphene about a decade ago. The dangling-bond-free lattice has made it feasible to integrate these materials with highly disparate atomic layers, such as industrial silicon substrates, to create a wide spectrum of van der Waals heterostructures without the constraints of lattice matching and processing …

With a strong chemical sensitivity, high-resolution high angle annular dark field (HADDF)-scanning transmission electron microscopy (STEM) is widely used for acquiring detailed structural information in materials. The precise displacement of B-site ions with respect to the center of A-site ions in perovskites can be further mapped which is direct evidence for topological structures. As the topological entities have great potential …

We numerically study the phase ordering dynamics of a uniform 2D Bose gas following a quench into the superfluid phase, using the classical field methodology. We explore the crossover between conservative and dissipative evolution, finding clear evidence for universal behaviour in the dynamics, regardless of the dissipation strength. This universal behaviour manifests as a power-law growth of the correlation length …

The recently discovered anti-ferromagnetic topological insulator MnBi2Te4 (MBT) has been proved to host rich topological phases such as quantum anomalous Hall (QAH) and axion insulator phase in its thin films. A transition from a large gap 2D Ferromagnetic (FM) insulator in 1 Septuple layer (SL) to 5SL QAH insulator has been reported [1]. 1SL MBT has a wide gap exceeding …

  Whilst often discussed as non-trivial phases of low-dimensional ferroelectrics, modulated polar phases such as the dipolar maze and the nano-bubble state have been appraised as essentially distinct. Here we emphasize their topological nature and show that these self-patterned polar states, but also additional mesophases such as the disconnected labyrinthine phase and the mixed bimeron-skyrmion phase, can be fathomed in …

Topological insulators (Tis) are a promising candidate for future low-energy electronics technologies, and the 2D or quantum spin hall (QSH) insulator (Bernevig, 2006) has attracted much attention for its 2e^2/h conductance regardless of width. This conductance is characterised by two helical edge states that have correlated spin polarization and momenta (Qi, 2011). This correlation acts to explicitly prevent backscatter, as …

About the presenter Hien Nguyen is a PhD candidate in materials science and engineering working with Prof Jan Seidel at UNSW Sydney, where she studies nanoscale properties of multiferroic materials and growth of atomically thin films by pulsed laser deposition on different substrates, and investigates electric, magnetic properties of these materials as well as phase transitions and topotactic transformations in …

About the presenter Dr Guangyao Li is a postdoc researcher working with A/Prof Meera Parish and Dr Jesper Levinsen at Monash University within FLEET’s Research themes 2 (exciton superfluids) and 3 (light-transformed materials). His research interests include dynamics of polariton condensates, chiral states at exceptional points, topological excitations in open-dissipative superfluid, and the spin-orbit interaction of light.

About the presenter Frank Yun is a Research Fellow working with CI Xiaolin Wang at the University of Wollongong.

About the presenter Dhaneesh Kumar Gopalakrishnan is an PhD student working with Dr Agustin Schiffrin at Monash University. Within FLEET’s research theme 1 and Enabling technology theme A, Dhaneesh synthesises and characterises 2D organic-based materials, searching for those that exhibit topological electronic properties. Synthesis and characterisation of these materials are carried out in the state-of-the-art scanning probe microscopy set-up in …

About the presenter Dr Daniel Sando is a postdoctoral researcher working with Prof Nagy Valanoor at UNSW to fabricate and characterise topological materials for FLEET’s Research Theme 1 and Enabling technology theme A. Dr Sando’s research is focused on the growth of 2-dimensional electron systems (2DES) comprising oxide perovskite materials LaAlO3 and SrTiO3, by pulsed laser deposition (PLD). A specific …

About the presenter Bernard is pursuing a PhD with CIs Agustin Schiffrin and Nikhil Medhekar, working on calculating the properties of novel electronic materials using ab initio (first principles) calculations with density functional theory within FLEET’s Research Theme 1. In 2018, Bernard received the Rodney L Turner Prize for the Best Honours Thesis in Physics and Astronomy, and the JJ …

About the presenter Benjamin Lowe is a PhD student at Monash University where he works in Research theme 1 with Dr Agustin Schiffrin studying the self-assembly of metal-organic systems using a state-of-the-art scanning probe microscopy (SPM)facility that allows metal-organic systems to be engineered and probed with atomic-scale precision. He seeks to develop systems with electronic and opto-electronic properties that are …

About the presenter Tommy is a PhD student and condensed matter theoretical physicist at RMIT university under the supervision of Jared Cole. Within FLEET he works in Research theme 1: topological materials.

About the presenter Tatek Lemma is a PhD student working with CI Jeff Davis in FLEET’s Research Theme 3 and in Research theme 2. For his PhD, he is working on the investigation of topological phase transition in a 2D semiconductor using the state-of-the-art Coherent multidimensional spectroscopy.

About the presenter Rishabh Mishra is a PhD Student working with A/Prof Jeff Davis‘s Ultrafast Spectroscopy group at Swinburne University of Technology. Contributing to FLEET’s Research Theme 3, Light-transformed Materials, Rishabh and Jeff aim to study the electronic correlations and ultrafast coherent dynamics in non-equilibrium quantum matter using coherent multi-dimensional spectroscopy.

About the presenter Dr Pankaj Sharma is a postdoctoral research associate working with A/Prof Jan Seidel at UNSW. Dr Sharma’s expertise lies in the area of scanning probe microscopy techniques and ferroelectric complex-oxides. Within FLEET, Dr Sharma is working on electric-field induced controlled rewritable manipulation of topological interfaces such as ferroelectric domain walls, and LaAlO3/SrTiO3 hetero-interfaces at the nanometre length …

About the presenter Oliver is a PhD student studying with Nagarajan Valanoor (UNSW). Oliver specialises in fabrication and characterisation of thin film heterostructures. He uses pulsed laser deposition (PLD) and laser molecular beam epitaxy (LMBE) to fabricate the desired materials, and uses high-resolution X-ray diffraction, piezoresponse force microscopy (PFM), magnetometry and neutron scattering in characterization of the materials. In terms …

About the presenter Dr Jack Hellerstedt is a research fellow working with CI Agustin Schiffrin at Monash University.

About the presenter Yi-Hsun Chen is an experimental physicist working with Prof Michael Fuhrer and Dr Chen Shao-Yu at Monash University, where he researches Bose-Einstein condensates using devices constructed using 2D materials, seeking exciton superfluids in 2D material quantum wells. His research falls under FLEET research theme 2 exciton superfluids. For his PhD project, he is using 2D materials to create …

About the presenter Dr Dmitry Efimkin is a Scientific Associate Investigator at Monash University specialising in novel materials such as Dirac materials, graphene and topological insulators, and optical phenomena in solids. Within FLEET, Dmitry works with Michael Fuhrer, Meera Parish, and Nkhil Medhekar in Research theme 2: exciton superfluids and Enabling technology A: atomically-thin materials, studying optical and collective phenomena …

About the presenter Daniel McEwen is an Honours student working with CI Michael Fuhrer at Monash University.

About the presenter Dr Son Ho is a postdoctoral research fellow working with Prof Jared Cole at RMIT, applying analytical and computational approaches to investigate the theory of electronic transport in topological materials for FLEET’s Research Theme 1: topological materials.

About the presenter Vivasha Govinden is a PhD student working with Prof Nagy Valanoor at UNSW to investigate ferroelectric coupling with the introduction of a spacer between ferroelectric thin films, leading to exotic ferroelectric domains that can contribute to a giant electromechanical response. An enhanced electromechanical response is key to applications in nanoelectronic sensors, memory and logic devices and electromechanical …

About the presenter Qingdong Ou is a research fellow working with Prof Michael Fuhrer at Monash University to study nano-device fabrication based on 2D materials, within FLEET’s Enabling technology B. Qingdong is seeking to minimize energy losses in light-matter interactions, aiming to realise ultra-low energy consumption in 2D-semiconductor-based optoelectronics. He also studies carrier behaviour via microscale photoluminescence and photocurrent mapping, and …

About the presenter Karen Bayros is a PhD student working with Jared Cole and Jackson Smith at RMIT where she models current flow through dielectric barriers in superconducting quantum bits. The influence of defects and imperfections can limit the dissipationless flow-through devices comprised of these barriers, and Karen uses advanced computational models to understand the interplay between the molecular structure …

About the presenter Jack Muir is a PhD student working with Assoc Prof Jeffrey Davis’ ultrafast spectroscopy group at Swinburne FLEET node, contributing to Research Theme 2. In his project, Jack aims to explore the ultrafast dynamics of two-dimensional transition metal dichalcogenide van der Waals heterostructures, with a particular interest in the effects of Moire potentials.

About the presenter Fan Ji is a PhD student working with A/Prof Jan Seidel at UNSW. Her research focuses on understanding and improving the nanoscale functionality of oxide heterostructures such as LAO/STO by means of scanning-probe based nanolithography and characterisation methods. She also explores reversible control of the two-dimensional electron gas at oxide interfaces and its applicability to quantum devices. …

About the presenter Allan Pennings is a PhD Student working with Prof Chris Vale and Dr Sascha Hoinka, with the goal of building the Australian Quantum Gas Microscope. Contributing to FLEET’s Research Theme 3, Light-transformed Materials, his project focused on different techniques of dark field imaging with X-rays. Allan recently completed his Honours at Monash followed a Bachelor of Science (Physics) …

About the presenter Zeb Krix is a PhD student at UNSW, where he studies the theory behind artificial graphene and artificial topological insulators, which are 2D materials with an imposed superlattice structure. Zeb models such systems in the presence of a perpendicular magnetic field in order to improve understanding of the relevant electronic transport measurements. This work is closely linked …

About the presenter Yik-Kheng Lee is a PhD student at RMIT University, working with Prof Jared Cole, following his Honours project with FLEET which was on modelling the transport properties of a two-dimensional electron gas. His research interests are in the field of topological materials, under FLEET’s research theme 1.

About the presenter Peng Liu is a Research Associate with CI Xiaolin Wang at the University of Wollongong. He works within FLEET’s Research theme 1 and Enabling technology theme A. He is exploring the structural and transport properties of 2D superconducting materials, with focus in electric-field gating and transmission electron microscopy.

About the presenter Peggy Schoenherr is an experimentalist physicist with Prof Jan Seidel (UNSW), where she studies materials’ magnetic, electric and mechanical properties at the nanoscale using room-temperature and low-temperature atomic force microscopy.  The materials investigated span a wide range from superconductors to skyrmion systems to ferroic materials, with all of them potentially exhibiting the topological structures (domain walls, vortices, …

About the presenter Matthew Weidman is a group leader working with PI Ferenc Krausz at the Max-Planck institute of Quantum Optics.

About the presenter Dr Karen Livesey is a theoretical condensed matter physicist based at the University of Newcastle and is a Scientific Associate Investigator in FLEET. Her research interests are in (i) exotic behaviours in magnetic thin films, and (ii) magnetic nanoparticles for biomedical applications. It is the first research area (magnetic thin films) that overlaps with the research themes within FLEET. Her …

About the presenter Dr Ivan Herrera is a Research Fellow at Swinburne University of Technology who performs experimental research to investigate universal phenomena at the few-body and many-body level in ultracold 2D gases of fermionic atoms. Ivan works within Research Theme 3: Light-transformed materials with CI Chris Vale.

About the presenter Dr Hong Liu is currently working with CI Nikhil Medhekar and AI Dmitry Efimkin, exploring spin-orbit coupling and interaction effect in topological materials theoretically. As a member of Research theme 1 team, she aims to understand the criteria for protection against dissipation and also include the operational criteria for achieving dissipationless transport.

About the presenter Dr Harley Scammell is a postdoctoral researcher working with Prof Oleg Sushkov at UNSW on the theory of artificial graphene in FLEET’s Research Theme 1, topological materials. Dr Scammell’s research focusses on the interplay of various tuning parameters – such as strain and spin-orbit coupling – on the electronic properties of artificial graphene. Key considerations are additional, …

Classical electromagnetism is linear, however  strong fields varying slowly at the electron rest energy scale, polarize the quantum vacuum and give rise to nonlinear phenomena, such as scattering or splitting of photons and birefringence. These effects become relevant only in very strong fields that exist in exotic environments e.g. in the vicinity of heavy nuclei or neutron stars. We show …

About the presenter Phat Tan Nguyen is a PhD student working under the supervision of Dr Agustin Schiffrin and Dr Gary Beane at Monash University, where he is investigating optically-driven topological phases of matter using terahertz time-domain spectroscopy and pump-probe spectroscopy with sub-picosecond time resolution, and at the scale of a single atom. He is mainly involved in Research theme …

About the presenter Mitko Oldfield is an experimental physicist specialising in terahertz time-domain spectroscopy and exciton-polariton condensation, working with Dr Agustin Schiffrin and Dr Gary Beane at Monash University within FLEET’s research theme 2 and research theme 3. Mikto’s research focuses on forming a polariton condensate in high Q-factor microcavities through the use of a terahertz pumping beam generated via …

About the presenter Joshua Gray is a PhD student working with Prof Jared Cole at RMIT University.

About the presenters Dr Aiswarya Pradeepkumar and PhD student David Katzmarek work with Prof Francesca Iacopi, head of Communications and Electronics, in the Faculty of Engineering and IT, UTS. Within FLEET, Francesca is an associate investigator working on graphene for low-energy electronic devices. She also liaises with the IRDS, advising potential applications and integration strategies for novel technologies generated by FLEET …

About the presenter Eliezer Estrecho studies the behaviour of exciton-polaritons as part of FLEET’s research theme 2, exciton superfluids, working with Elena Ostrovskaya at the ANU. He is currently studying condensation of polaritons in gallium-arsenide-based microcavities using single-shot experiments and large optically induced traps. He is also working on creating polariton condensates using atomically-thin materials.

About the presenter Wafa Afzal is a PhD student and experimental condensed-matter physicist working with Prof Xiaolin Wang at the University of Wollongong, with experience in thin-films of magnetic nanoparticle dispersions in polymers, and has studied surface and magnetic states of these films using atomic force microscopy and magnetic force microscopy. For her PhD within FLEET’s Enabling Technology Theme A …

About the presenter Alexander Nguyen is a materials engineer working with Dr Julie Karel at Monash University, where he performs magnetoelectronic transport measurements on amorphous topological insulators within FLEET’s research theme 1 and enabling technology B. An important aim is to experimentally realise topologically-protected states in an amorphous material, which may offer some benefits over crystalline materials.  Another major career …

About the presenter Patrick Taylor is a PhD student working with Prof Michelle Spencer at RMIT University

About the speakerDr Shao-Yu Chen is a research fellow working with Prof Michael Fuhrer at Monash University to realising Bose-Einstein Condensation of tightly bound excitons in 2D semiconductors. He has extensive research experiences on transport and optical measurement on 2D materials including graphene and transition metal dichalcogenides (TMDs). In particular, he has investigated strong Coulomb interaction and many-body correlation in …

Using Multidimensional Coherent Spectroscopy (MDCS), we have revealed quantum superpositions among low energy states in an optimally doped cuprate superconductor that remain coherent for more than 500fs.  This observation points to a strong correlation between the low energy modes (e.g. phonons, magnons, charge density waves, or many body electron states, etc) and the optically excited states.  These correlations are mediated …

Designed to debunk the myths around unconscious bias and to help you better understand what can be done in a workplace to ensure that biases (conscious or unconscious) are neutralised. This session discusses: 1.Diversity and inclusion 2.What unconscious bias is 3.How humans process information 4.Ways to identify areas of unconscious bias 5.Micro aggressions 6.Some of the impacts of unconscious bias …

The study of many-body quantum systems with strong inter-particle interactions is of great interest for the understanding of novel materials. Ultracold atomic gases allow the precise tuning of interactions between atoms via a Feshbach resonance. We experimentally realise such gases with fermionic atoms at unitarity exhibiting the strongest interactions allowed by quantum mechanics. Using two-photon Bragg spectroscopy, we study the …

The emergence of atomically thin materials post graphene, has opened up new avenues for the engineering of electronic states via van-der-Waals heterostructures. For instance, tunable large bandgap 2D topological insulators, such as quantum spin Hall (QSH) insulators, have recently shown promise for device applications above 100K. On the other extreme of temperature, van-der-Waals heterostructures of QSH insulators can offer a …

Working in academia is both an exciting and challenging experience. It can be an emotional roller-coaster. The excitement of working on something you care about, sharing ideas with students and colleagues and making a contribution to knowledge. The challenges of feeling isolated and overwhelmed, dealing with setbacks, uncertainty, conflict and loss of motivation. Inevitably over the course of your career …

Prof. David Neilson, University of Antwerp Although there is strong theoretical and experimental evidence for electron-hole superfluidity in separated sheets of electrons and holes at low T, extending superfluidity to high T is limited by strong 2D fluctuations and Berezinskii-Kosterlitz-Thouless topological effects.  We show this limitation can be overcome using a superlattice of alternating electron-doped and hole-doped semiconductor monolayers.  The superfluid transition in a …

Triply degenerate point (TP) fermions in tungsten-carbide-type materials (e.g., MoP), which represent new topological states of quantum matter, have generated immense interest recently. However, the TPs in these materials are found to be far below the Fermi level, leading to the TP fermions having less contribution to low-energy quasiparticle excitations. Here, we theoretically predict the existence of TP fermions with …

The MacDiarmid Institute was founded in 2002, with a vision of economic transformation through excellence and capability development in materials science, and with a broad mandate to work beyond the lab bench. 17 years on, this talk will focus on some of the ways in which the Institute is leading culture change; from entrepreneurship leading to 17 spinout companies, to …

When the relative rotation between two sheets of graphene is set to be close to special angles (referred to in the literature as “magic angles”), the low-energy effective theory features Dirac fermions with very flat bands.  Interest in understanding the competing mechanisms at play was reignited recently with the experimental observations of superconductivity and strongly correlated insulating phases in such …

Chutian Wang, Monash University One of the key challenges in design of devices bases on topological materials is to conveniently turn the surface and edge states on and off. Two-dimensional (2D) topological crystalline insulators (TCI) are ideal materials for achieving this switch, as their edge states can be turned on/off by applying a symmetry-breaking field. However, it remains unresolved how …

The quantum impurity problem is relevant to a range of different systems in physics, and it continues to be a highly active area of research. In ultracold atomic gases, the impurity problem can be realised by introducing a small number of atoms of a different species into a background gas. The interaction between the impurity and the background medium can …

About the speaker Vivasha Govinden is a PhD student working with Prof Nagy Valanoor at UNSW to investigate ferroelectric coupling with the introduction of a spacer between ferroelectric thin films, leading to exotic ferroelectric domains that can contribute to a giant electromechanical response. An enhanced electromechanical response is key to applications in nanoelectronic sensors, memory and logic devices and electromechanical …

With no requirements for lattice matching, van der Waals (vdW) ferromagnetic materials are rapidly establishing themselves as effective building blocks for next-generation spintronic devices. We report a hitherto rarely seen antisymmetric magnetoresistance (MR) effect in vdW heterostructured Fe3GeTe2 (FGT)/graphite/FGT devices. Unlike conventional giant MR (GMR), which is characterized by two resistance states, the MR in these vdW heterostructures features distinct high-, …

Qi Zhang1, Sergei Prokhorenko2, Yousra Nahas2, Lin Xie3, Laurent Bellaiche2,  Alexei Gruverman4 and Nagarajan Valanoor1 1School of Materials Science and Engineering, The University of New South Wales,  Sydney,  New South Wales 2052, Australia; 2 Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, AR 72701, USA; 3Department of Physics, Southern University of Science and Technology, Shenzhen, 518055 …

Coexistence of reversible polar distortions and metallicity leading to a ferroelectric metal, first suggested by Anderson and Blount in 1965, has so far remained elusive. Electrically switchable intrinsic electric polarization, together with the direct observation of ferroelectric domains, has not yet been realized in a bulk crystalline metal, although incomplete screening by mobile conduction charges should, in principle, be possible. …

The rectified non-linear response of a clean undoped semiconductor to an ac electric field includes a well known intrinsic contribution — the shift current. We show that when Kramers degeneracy is broken, a distinct second-order rectified response appears that is due to Bloch state anomalous velocities in a system with an oscillating Fermi surface. This effect, which we refer to …

One of the goals of FLEET is to develop transistor technology using superfluid circuits.   In collaboration with the ARC Centre of Excellence for Engineered Quantum Systems, we experimentally realize a highly-tunable superfluid oscillator circuit in a quantum gas of ultracold atoms, and develop and verify a simple lumped-element description of this circuit. At low oscillator currents, we demonstrate that …

We use non-equilibrium Green’s functions, tight-binding and effective models to understand transport in a range of nanoscale devices. In 2019, this has included developing a new tight-binding model for low-dimensional allotropes of Bismuth (with the Monash node), studying the effects of spin-orbit coupling in two-dimensional electron gases (with the UNSW node), and Majorana fermions in nanowires. In addition, we have …

I study the phase diagram of two dimensional electron systems with Rashba and Dresselhaus spin orbit coupling systems. And we find there are two Fermi Liquid phase which have no spin polarisation. In addition, there is also a in plane spin polarisation phase. We also find a out-of-plane spin polarisation phase by Monte-Carlo simulation, which we are still study on …

In this talk I will discuss the steps we have taken so far in pursuing the goal of synthesising a 2D organic topological insulator comprised of 9,10-dicyanoanthracene (DCA) as the organic species. In particular, I will discuss our recently published results regarding a formation of a sub-monolayer of DCA molecules on Ag(111) where the individual molecular species exhibit charging when …

Polar bubble domains are complex topological defects akin to magnetic skyrmions that can spontaneously form in ferroelectric thin films and superlattices. They can be deterministically written and deleted and exhibit a set of properties, such as sub-10 nm radius and room- temperature stability, that are highly attractive for dense data storage and recongurable nano-electronics technologies. However, possibilities of controlled motion …