Anomalous Hall effects, such as the valley, the orbital, and the spin Hall effect, are usually detected by measuring the accumulation of the corresponding densities (valley, orbital, or spin density) on the edges of a bar-shaped device (Hall bar). However, the relation between this accumulation and the bulk current, which is supposed to "feed" the accumulation, is far from straightforward. For example a BN nanoribbon with Fermi level in the gap supports a bulk valley Hall current in spite of being an insulator. However, this "undergap" current does not produce a valley density accumulation as long as there are no edge states crossing the Fermi level. Therefore we see that there is no direct connection between the magnitude of the bulk valley current (quantified by a finite valley Hall conductivity) and the magnitude of the edge accumulation (zero in this case). The reason for this puzzling state of affairs is that the conservation of the valley density (as well as the orbital magnetic moment density and other densities that depend on crystal momentum) is broken in an unexpected way by the very same electric field that drives the valley Hall effect. It turns out that the relation between edge accumulations and bulk current for non-conserved densities is a delicate one, which necessarily involves dissipation from bulk and/or edge state at the Fermi level. We provide an exact formula, based on linear response theory, for calculating the effective bulk current that feeds the accumulation, and show that it can be expressed as a Fermi surface average, which depends critically on the presence or absence of localized edge states at the Fermi level as well as the reflection coefficients of extended bulk states at the edges of the system. We argue that this formula can be used to accurately model the density accumulations in experimental measurements of the valley Hall effect.

* This talk is based on the paper by Alexander Kazantsev, Amelia Mills, Eoin O'Neill, Hao Sun, Giovanni Vignale, Alessandro Principi, arXiv:2211.12428

Functionality of novel nanomaterials and their impact on society will be ultimately dictated by our ability to precisely control their structural properties, size uniformity, and dopant distribution at the atomic level. In this presentation, we will discuss our recent efforts on the implementation of nanomaterials – including two dimensional (2D) ultrathin films, one dimensional (1D) nanowires/nanotubes, and zero dimensional (0D) nanocrystals – into real-world applications. First, we will discuss recent initiatives within the Applied Materials-NUS Advanced Materials Corporate Lab with a special focus on the wafer-scale integration of 2D materials for the current and future semiconductor industry nodes. Furthermore, we will discuss a new type of freestanding down-conversion color filters based on colloidal 1D quantum dots for the next generation of high-resolution displays. An outlook on new ways to tailor properties of nanomaterials using highly focused ion- and electron-beams or a twist will be presented.

Among other, ultracold atoms’ platforms are currently used as simulators in quantum physics. One of the drawback of atoms is their lack of charge preventing simulations of magnetism to target important effects such as quantum Hall or high-Tc surperconductivity to name a few. However, one can partially lift this limitation with engineered light-atom couplings, leading to the appearance of artificial Gauge fields. Interestingly, the generation of gauge fields does not only act on an effective charge but also on higher dimensional quantum objects such as pseudo-spin or pseudo-color-charge. In this talk, I will discuss how we were able to experimentally generate and control those high dimensionality gauge fields. I will also present few illustrative examples where we take advantage of the richness of such systems to generate geometric Qubits, simulate Dirac equation, and perform new type of Ramsey interferometry.

Single-photon technologies allow the generation, manipulation, and detection of light at its fundamental limit. They form the cornerstone of photonic quantum information processing. Besides stringent performance metrics, practical quantum systems for computation and simulation further impose demanding requirements on scalability. In this talk, we will discuss several critical technologies for scalable single-photon generation, manipulation, and detection, with a particular emphasis on integrated photonics solutions. Specifically, we first introduce thin-film lithium niobate as an emerging material platform for integrated quantum photonics, demonstrating how it enables efficient single-photon generation, spectral control, and coherent transduction. We then present superconducting nanowires as outstanding single-photon detectors, highlighting recent advances in their scalable readout and on-chip integration. Combining both paves the way towards fully integrated quantum photonic processors.

A talk on the implications of and efforts behind finding the faintest galaxies, as well as Prof. Burçin’s outreach programs on bringing scientific efforts and discoveries to the community.

The talk also is an opportunity for the physics community to engage with the EDIphy team on diversity in physics in a casual setting. Please register for the event here.

Catalysts open up new reaction pathways which can speed up chemical reactions while not consuming the catalyst. A similar phenomenon has been discovered in quantum information science, where physical transformations become possible by utilizing a (quantum) degree of freedom that remains unchanged throughout the process. In this talk, I give a comprehensive overview of the concept of catalysis in quantum information science and discuss its applications in various physical contexts.

Fusion is one of the great challenges in this century, as it potentially provides a clean, safe and virtually inexhaustible source of energy. Confining hot plasmas with intense magnetic fields is one promising path towards a commercially viable reactor. A major step in this direction will be reached with the ITER international project, under construction in France, and expected to start operation in 2030. The seminar will start with an introduction to plasma physics and technology for magnetic confinement fusion, with some focus on tokamaks – the most advanced magnetic configurations so far. The main results on theory, modelling and experiments will be summarised. Alternative schemes to tokamaks will also be presented, in view of recent developments and initiatives in the private sector.

This thriving field of experimental research begs for a robust programme in theory and modelling in order to interpret results, prepare future experiments, and design future reactors. An ambitious research programme has been devised in Singapore, in collaboration with foreign laboratories, which aims at modelling fusion plasmas, based on ab initio simulations, theoretical plasma physics and AI algorithms. Also diagnostics to characterise fusion burning plasmas and means to control it will be developed. This challenging programme will be detailed and commented.