Category Archive

Quasiparticles with Weyl dispersion can display an abundance of novel topological, thermodynamic and transport phenomena, which is why novel Weyl materials and platforms for Weyl physics are being intensively looked for in electronic, magnetic, photonic and acoustic systems. We demonstrate that conducting materials in magnetic fields generically host Weyl excitations due to the hybridization of phonons with helicons, collective neutral …

In this poster I will review how cold neutrons can be used to detect the phonons, magnons and magnetic structure of quantum materials. As an example I will present measurements of the phonon bandstructure in graphene and Bi2Te3. I will discuss the upcoming upgrade to the ANSTO cold neutron source scheduled for 2024. About the presenter David Cortie is a …

Two-dimensional topological insulators possess a single conducting channel embedded inside the insulating bulk surface bandgap, which can be complicated to realize in practical devices due to electron-phonon interactions (EPI) at finite temperatures. Using single bilayer Bi (111) (SBB) and the first-principles method, we show that the EPI strongly depend on the edge states dispersion. Particularly, when the dispersion of the …

Monolayer WTe2 has been predicted to have zero resistance along its 1D edge as backscattering is protected by time reversal symmetry. However, experiments reveal significant resistance at length scales of 100nm. This project aims to fabricate WTe2 devices and characterise the various scattering mechanisms along the quantum spin hall edge state. About the presenter Daniel McEwan is a PhD Student …

Exciton-polaritons (polaritons herein) are bosonic quasiparticles formed when an exciton is coupled to a cavity photon in a semiconductor microcavity [1]. These hybrid light-matter quasiparticles form Bose-Einstein condensates at elevated temperatures due to their very small effective mass. However, polariton condensates are inherently non-equilibrium because of the ultrashort lifetime of polaritons and coexistence with a reservoir of high-energy excitons feeding …

The highly tunable band structure and eightfold degeneracy of the zero-energy Landau level (zLL) of bilayer graphene (BLG) makes it an ideal platform for engineering new quantum Hall states, denoted by the orbital, valley, and spin quantum numbers. However, determining the filling sequence of these quantum states at different electric fields is still an unresolved question. We build an effective …

Transition metal dichalcogenides (TMD) are atomically thin materials described by MX2, where M is a transition metal (like Mo or W) and X is a chalcogen atom (like S, Se or Te). A pair of twisted TMD monolayers makes a nanostructure. In this synthetic material a plethora of phenomena related to electronic correlations such as superconductivity, topological non-trivial effects or …

The past decade has seen intense focus on realising hybrid semiconducting-superconducting nanowires which exhibit Majorana Zero Modes (MZMs) in a nontrivial topological phase. This has been particularly motivated by the non-Abelian statistics of MZMs and their application in performing topological quantum computation. A quantised zero-bias peak in conductance transport measurements is seen as the hallmark of MZMs. However, it has …

2D nanomaterials are promising in next-generation miniatured on-chip optical devices. However, their ultra-small thicknesses and limited lateral dimensions hinder the characterization using conventional techniques, especially for complex refractive indices measurement. Here, we propose a silicon photonics-enabled platform to evaluate the complex refractive indices of ultrathin 2D materials in a facile and reliable manner. Ultrathin molybdenum oxides (MoOx) with multiple stoichiometric …

The interplay of the topology of electronic wavefunctions with spin configurations in intrinsically magnetic topological insulators (TIs) causes various exotic topological states, which attracts much attention in condensed matter physics. In this work, we study the magnetic and electronic properties and edge states of two-dimensional CoBi2Te4. Based on our density functional theory and tight-binding calculations, CoBi2Te4 films are predicted to …

Recent experiments on two-dimensional artificial crystals have revealed a set of magnetic oscillations with unexpected frequencies. We present a theory of these oscillations and show that they are of a kind not previously observed in artificial crystals or in real metals. In particular, we show that they arise from open electron trajectories. About the presenter Zeb Krix is a Research …

The spatial separation of charge carriers with different spins is an important step towards building spintronics devices. Transverse magnetic focusing relies on large spin-orbit coupling to accomplish this task. Two-dimensional hole gases naturally exhibit large spin-orbit coupling and are therefore good candidates for realising transverse magnetic focusing based spin filters. However, in recent experiments, the correct interpretation of the different …

Monolayer tungsten diselenide (1L-WSe2) has recently received attention because of its favourable band structure for probing novel correlated phenomena of p-type carriers, such as interaction-driven and topological insulating phases and superconductivity in twisted bilayers, and Bose-Einstein condensation of excitons in double-layer heterostructures. However, electrical transport studies have been impeded by the lack of a reliable method to realize Ohmic hole-conducting …

An impurity particle interacting with a Bose-Einstein condensate (BEC) leads to the formation of a quasiparticle known as the Bose polaron. We investigate the properties of the two-dimensional Bose polaron, applying a variational ansatz that contains up to two Bogoliubov excitations of the BEC. Similar to its three-dimensional counterpart, we observe the existence of two quasiparticle branches, namely the attractive …

Australian Postgraduate Research Intern (APR.Intern) is Australia’s only national PhD and Masters by Research internship program spanning all sectors and disciplines. APR.Intern connects postgraduate research students with industry through short-term placements, empowering students to thrive in a practical research environment. For businesses, APR.Intern is a platform to access Australia’s brightest emerging research talent and accelerate innovation. About the presenter Justin …

Atomically-thin InSe exhibited strong PL emission from its dark excitons due to efficient acoustic-phonon-exciton coupling, resulting in high population density and efficient radiative recombination. The asymmetric lineshape observed in the PL emission is explained by the carrier localization model, attributed to nonuniform surface potentials. About the presenter Shao-Yu Chen is a Scientific Associate Investigator from the National Taiwan University, collaborating …

We investigate the formation of excitons bound by photons using a microscopic Hamiltonian involving quantum well electrons, holes, and microcavity photons. The negative reduced effective mass of the quantum well electron-hole (e-h) pair prevents Coulomb bound excitonic states, but the microcavity photon is capable of inducing binding. Using a theory based on Green’s functions we have calculated the spectral response …

Two-dimensional van der Waals (vdW) materials are materials whose crystal structure features neutral, single-atom-thick or polyhedral-thick layers of atoms with covalent or ionic bonding along two dimensions and van der Waals bonding along the third axis. The weak van der Waals bonding energies ( ̴40-70 meV) enable these 2D materials to be mechanically or chemically exfoliated into a few or …

In high entropy oxides, competition between many different magnetic exchange interactions leads to mixed magnetic states. We have grown thin films of La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 (L5BO), which normally shows an antiferromagnetic ground state, but this should shift to a ferromagnetic ground state as the concentration of Mn increases. We aim to investigate how L5BO performs as a spintronic oxide at the transition …

An electron doping dependent trion splitting in WS2 monolayer is reported. The corresponding mechanisms are discussed. About the presenter Leo Jia is a Research Fellow at Swinburne University with CI Jeff Davis, working on research projects as part of FLEET’s Research Theme 1, Topological Dissipationless.

Long one dimensional wires are a prerequisite for topological qubits – a form of qubit that is robust against decoherence[1]. Topological qubits utilise Majorana Zero Modes – a quasiparticle that is it’s own antiparticle. A majority of the work done on topological qubits have used one dimensional systems with high disorder[2][3][4]. Disorder masks the signatures of Majorana Zero Modes, making …

We investigate interactions between polaritons and a dark excitonic reservoir in a 2D system where the excitons are tightly-bound. The resulting energy spectrum is found to display several interesting features, including the appearance of a new energy mode related to a biexcitonic bound state, an apparent reduction in the Rabi splitting between the lower and upper polariton branches as the …

The electronic properties of two-dimensional (2D) metal-organic frameworks (MOFs) are largely dictated by their crystalline structure and can be fine-tuned by substituting metal or organic precursors for analogous counterparts (e.g. Cu atoms for Au atoms). One particular class of MOFs that form a 2D honeycomb-Kagome crystal are interesting for their potential to host correlated-electron phases. The aim of my project …

Previously we developed theory to increase viscous effects in hydrodynamic flow in a GaAs heterostructure using 1D modulated superlattice of micromagnets. This work featured the extraordinary no-stress boundary condition that has only been experimentally realised in electron hydrodynamics in GaAs. We now extend this work to the more general finite-slip boundary condition and detail an experimental set up for monolayer …

The mutual interplay between electron transport and magnetism has attracted considerable attention in recent years, primarily motivated by strategies to manipulate magnetic degrees of freedom electrically, such as spin-orbit torques and domain wall motion. Within this field the topological Hall effect, which originates from scalar spin chirality, is an example of inter-band quantum coherence induced by real-space inhomogeneous magnetic textures, …

We consider the Cooper pairing of Dirac electrons and conventional holes that can be engineered in topological the insulator/quantum-well double layer heterostructures. The helical nature of Dirac electrons manifests in the presence of two (almost) degenerate channels for the Cooper pairing. Being stable and matastable, both of these states are characterized by distinct Chern numbers are topological condensates. We discuss …

As the Earth rotates, the Coriolis force causes several oceanic and atmospheric waves to be trapped along the equator, including Kelvin, Yanai, Rossby, and Poincaré modes. It has been demonstrated that the mathematical origin of these waves is related to the nontrivial topology of the underlying hydrodynamic equations. Inspired by recent observations of Bose-Einstein condensation (BEC) in bubble-shaped traps in …

Cold neutrons can be spin-polarised and reflected from interfaces. This technique can be used to reveal the magnetic profile of ultra-thin films (

Liquid metal (LM) alloys are an interesting and emerging technology that holds a large potential in various applications. LM systems houses a sea of electrons in which holds potential in electronic based areas.1 For example, gallium-based alloys had widely been utilised in stretchable electronics and sensor-based technology research to date.1, 2 But what differentiates their uses depends entirely on their …