Over the past decade, the discovery of topological quantum matterโsuch as topological insulators, Weyl semimetals, and topological superconductorsโhas transformed condensed matter physics. Remarkably, many of these concepts are not confined to electrons in solids, but also apply to classical waves, from light and sound to water ripples and plasma oscillations.
In this talk, I will show how...
The interplay between topology and magnetism in quantum materials gives rise to novel quantum phases, characterized by topologically protected surface states with non-trivial electronic band structures and complex spin textures. One of the most compelling outcomes of this interplay is the quantum anomalous Hall effect (QAHE)ยน, where a single chiral edge mode enables dissipationless electron...
We present an analytical study of the ground-state phase digram of dilute two-dimensional spin-1/2 Fermi gases exhibiting d-wave altermagnetic spin splitting under s-wave pairing. Within the Bogoliubov-de Gennes mean-field framework, four distinct phases are identified: a Bardeen-Scheriffer-Cooper-type superfluidity, a normal metallic phase, a nodal superfluidity with topological...
Singlet fission (SF) is an electronic transition that in the last decade has been under the spotlight for its applications in optoelectronics, from photovoltaics to spintronics. Despite considerable experimental and theoretical advancements, optimizing SF in materials like multichromophoric systems and molecular crystals remains a challenge, due to the complexity of its analysis beyond...
Critical phenomena at finite temperature underpin a broad range of physical systems, yet their
study remains challenging due to computational bottlenecks near phase transitions. Quantum annealers have attracted significant interest as a potential tool for accessing finite temperature criticality beyond classical reach, but their utility in precisely resolving criticality has remained limited...
Topological insulators (TIs) are a class of materials that hosts insulating bulk states and topologically protected metallic surface states, arising from strong spin-orbit coupling and time-reversal symmetry1,2. When time-reversal symmetry is brokenโsuch as by introducing magnetismโthese surface states can become gapped, giving rise to novel quantum phases like quantum anomalous Hall effect...
We experimentally realise the theoretical proposal for in-situ tunable photonic edge states emerging from qubits coupled to a waveguide with a photonic bandgap. These edge-states are directional, exhibiting theoretically zero population in the opposite direction. Our experiment implements a tunable Rice-Mele waveguide configuration, where the directionality of edge states is controlled in-situ...
In light of the integration requirements of optoelectronic functional devices, the multifunctional optoelectronic crystal lithium niobate has emerged as a crucial matrix material. This development has imposed new demands on crystals, including uniformity of crystal structure, stoichiometric crystals, large diameter, and long equal diameter. Through the innovation of the growth technology of...
Biological function is closely linked to cell morphology and subcellular structure, making 3D imaging techniques an essential tool for understanding complex biological processes. Typically, 3D imaging involves staining and labelling, which can be time-consuming, error-prone, and reliant on toxic reagents. Imaging based on the intrinsic biophysical properties of cells and tissues, such as...
The natural mineral clinoatacamite, [Cu2Cl(OH)3], exhibits low-temperature, frustrated magnetic behaviour where competing interactions are responsible for novel magnetic properties. Attempts to establish the magnetic phases in this material have been undertaken and an unconventional applied field (H||b) phase diagram has been revealed [1]. Two critical transition temperatures at zero field...
High harmonic generation (HHG) is a physical effect which happens when a strong driving laser acts on atomic, molecular, or solid systems. As a result, a system emits at frequencies of integer multiples of the driving laser frequency [1]. It was also shown that including correlations between atoms can generate entangled and squeezed light or entangled photon pairs [2]. These can be an...
The effective design of new materials for sustainable energy conversion can be facilitated by the accurate prediction of electronic properties with moderate computational complexity and cost. The self-interaction error (SIE) of Kohn-Sham density functional theory (KS-DFT) is a non-physical, non-linear dependence of an orbital's energy on its own fractional occupation [Dabo et al., Phys. Rev....
In this work, fabrication of Mn3-xFexGa epitaxial thin films by using an ultra-high vacuum electron beam evaporation system, clarifying the relationship between composition of Fe, magnetic properties, crystal structure and film thickness were studied. The epitaxial growth of L21- ordered Mn-Fe-Ga thin films has been confirmed on the MgO (001) single crystalline substrate by using in-situ RHEED...
The search for novel semiconductors with sub-1 eV bandgaps is critical for efficient infrared photon-to-electricity conversion from high-temperature thermal emitters in thermophotovoltaic (TPV) systems. Double perovskites with the general formula AโBโฒBโณXโ offer exceptional chemical tunability, making them attractive for targeted infrared bandgap engineering. For TPV devices operating with...
This study investigates the impact of shear strain on the phase transformation behavior of Si and Ge under high-pressure conditions. Si and Ge are known to undergo a series of pressure-induced phase transformations, resulting in new phases with technological potential [1,2]. Utilizing both traditional diamond anvil cells (DAC) and a new rotational diamond anvil cell we demonstrate that...
Refrigeration is of vital importance for modern societyโfor example, for food storage and air conditioningโand 25 to 30 per cent of the worldโs electricity is consumed for refrigeration. Current refrigeration technology, mostly involving the conventional vapour compression cycle, is of growing environmental concern because of large amount of greenhouse gases released into atmosphere every...
While the optical properties of calcite are well known in the visible region, that same cannot be said of the terahertz region. Campbell et al. [1] have reported attenuated total reflectance (ATR) spectra. Sakai et al. [2] used pulsed terahertz radiation ATR. ATR has the attraction of experimental simplicity; however, the results are not always easy to interpret, nor is information related...
The Wombat instrument is one of a few neutron diffraction instruments in the world to have a large position sensitive (effective area) detector, which has greatly supported the wide range of science applications and outcomes the instrument is able to undertake [1]. To date there have been limited single crystal studies undertaken on the Wombat instrument due to peak integration software being...
Germanium-tin (GeSn) alloys have recently emerged as promising materials for infrared photodetectors due to their tunable bandgap, which ranges from the short-wavelength infrared (<3 ฮผm) to the mid-wavelength infrared (~3โ10 ฮผm). Ge-GeSn superlattices offer further advantages, including enhanced carrier confinement and improved absorption efficiency arising from quantum confinement effects....
Multiferroic materials have gained significant attention as promising candidates for next-generation electronic applications due to their ability to exhibit multiple ferroic orders simultaneously, including ferromagnetism and ferroelectricity [1]. Importantly, controlling magnetism by switching polarization states of ferroelectric materials offers more flexibility for information storage and...
Single-photon emitters (SPEs) are key components for quantum technologies, particularly in sensing and secure communication. In solids, SPEs often originate from point defects that introduce discrete states within the band gap. Electronโphonon coupling can strongly affect these defect levels by renormalizing their energies, thereby shifting the emitted photon energy. Common theoretical...
The global effort to develop a quantum computer is driving the search for scalable methods to manufacture quantum chips and qubits. One promising pathway is to adapt the mature and highly-scalable silicon manufacturing processes that underpin modern electronics. However, the demands on quantum devices are markedly different from those placed on conventional transistors. Quantum chips must...
Majorana modes (MMs), the elementary building blocks for the quantum bits of topological quantum computers, are known to suffer from hybridization when they get too close to each other. In that case, their wavefunctions start to overlap and the energy of the MMs is pushed to finite energies, causing errors during the braiding process of the MMs. Here we introduce negative hybridization, a...
Qubits based on Majorana zero modes (MZMs) in superconductorโsemiconductor nanowires have attracted intense interest as a platform for utility-scale quantum computing, due to their promise of intrinsically low error rates enabled by topological protection. These error rates are expected to be suppressed exponentially with increasing nanowire length or decreasing temperature. Here we identify a...
We present Fano-like resonances in silicon-on-insulator (SOI) nanowire resonators composed of coupled Sagnac interferometers (SIs). By tuning the reflectivity of each SI and the inter-coupling strength, we precisely control coherent mode interference to realize high-performance optical analogues of Fano resonances. The device, designed and fabricated on an SOI platform, is analyzed...
Point defects in spinor fields protected by topological invariants, the winding of the spinor configuration around the centre of the defect, have attracted a great amount of interests as they present a potential platform for spintronics and quantum communication. In this work, we present the generation of momentum-space pseudospin (polarization) defects in non-Hermitian exciton-polariton...
The discovery of the topological phases of matter sparked a renaissance in solid-state physics; however, broader applications to materials engineering are still in their infancy. Three-dimensional topological insulators offer a particularly simple new paradigm for developing unique functionality, which relies on the custom design of edges, surfaces, and interfaces.
The interplay between...
Magnetic thin films are important for computing technologies, where atomic-scale control of magnetic properties is required. Here, we present a 1D micromagnetic simulator (microM-ref1D) for thin film magnets with twisted magnetization profiles. Importantly, it is integrated with the Ref1D software for polarized neutron reflectometry fitting to accurately extract magnetic parameters.
Using...
Dissipative solitons and localized dissipative structures are ubiquitous, from optomechanics [1] to fluid dynamics [2], and even cosmological defects [3]. Dissipative solitons exist in systems far from equilibrium, where energy is continuously being lost and resupplied, which introduces unique properties distinct from analogous systems at equilibrium. These dynamics have been studied...
The established guiding principle for pulsed laser deposition (PLD) of high-quality YBaโCuโOโโโ (YBCO) superconducting films suggests that the optimal target-to-substrate distance (TSD) lies near the visible tip of the laser-induced plume, with deviations from this point expected to degrade film properties. We modified our PLD system to allow precise external TSD adjustment over a 110 mm range...
Spintronic devices offer fast, non-volatile, and more energy-efficient computing and memory compared to conventional electronic approaches. Compositionally complex oxides (CCOs) are an emerging class of materials for spintronic applications due to their low cost, robust magnetic stability, and high tunability. We are investigating $\mathrm{La(Cr_{0.2}Mn_{0.2}Fe_{0.2}Co_{0.2}Ni_{0.2})O_{3}}$...
Magnetic nanoparticles are used in biomedicine to treat and image cancer. This is because of their ability to generate heat within an alternating magnetic field and to track cells, respectively. Thus, it is important that their response to a magnetic field is simulated accurately to predict and understand their behaviour. However, simulations can be computationally expensive, so it is...
The ability to tailor functional properties of complex oxide thin films through epitaxial engineering has opened new avenues for oxide electronics and spintronics applications [1]. Lanthanum strontium manganite (La$_{1-x}$Sr$_{x}$MnO$_{3}$, LSMO) is a half-metallic perovskite oxide exhibiting a strong coupling among lattice strain, magnetism, and electronic transport [2]. Epitaxial strain...
