In second-order topological insulators (SOTIs), the bulk and surfaces are insulating, while the edges or hinges conduct current in a quasi-ideal (ballistic) manner, insensitive to disorder. As in the case of quantum spin Hall edges of 2D topological insulators, the current should be transported without dissipation by counter-propagating ballistic helical states with spin orientation locked to...
Einstein famously argued that energy has mass, which distorts spacetime. Conversely, as spacetime distorts, the energy density varies. This classical phenomenon applies even to massless particles: their thermal energy must vary in an inhomogeneous spacetime. The latter observation underlies an equivalence between a slowly varying temperature profile and a weakly curved spacetime. This...
Ta2NiSe5 (TNS) is an excitonic insulator candidate showing the semiconductor/semimetal-to-insulator (SI) transition below Tc=326 K. However, since a structural transition accompanies the SI transition, deciphering the role of electronic and lattice degrees of freedom in driving the SI transition has remained controversial. Here, I will present an investigation of the photoexcited...
The recent Kitaev model (2006) provides an exact model to achieve a quantum spin liquid ground state in a 2D honeycomb lattice system through Ising-like bond- dependent interactions [1]. While first considered as a toy model, a theoretical work from Jackeli and Khaliullin has paved the way towards the realization of Kitaev physics in bulk materials. They first showed that bond-dependent...
Strongly correlated systems are characterized by the fact that their low energy properties are not driven by the delocalization resulting from their kinetic energy, but by the effect of Coulomb’s repulsion between electrons. As a result they usually exhibit various ground-states that can be triggered using external conditions such as temperature, electric or magnetic fields, pressure,...
In this talk I shall introduce some basic notions of electronic neuromorphic
functionalities of materials and devices.
I shall first briefly describe our efforts towards implementing artificial neurons
exploiting the electric Mott transition. Then, I shall describe in more detail
our recent work implementing a new silicon-based memristive neuron. This
artificial spiking neuron is...
Topological materials are often predicted using crystal symmetries, although they don’t rely on them to exist. Our methodology thus excludes all amorphous materials, which are ubiquitous in technology and can display properties beyond those of crystals. In this talk I will present recent theoretical progress and experimental signatures of amorphous topological solids. I will discuss how to...
We report the possibility of obtaining Majorana zero modes (MZMs) in straight, highly perfect, and massively aligned atom-thin penta-silicene nanoribbons (p-SiNRs) with a very high aspect ratio, purely composed of silicon pentagonal building blocks, and grown by molecular beam epitaxy on the (110) surface a silver crystal template2,3. They could constitute the experimental realization of the...
Despite decades of intense researches, the enigmatic pseudo-gap (PG) phase of superconducting cuprates remains an unsolved mystery. In the last 15 years, condensed matter physicists discovered that this phase hosts symmetry breaking states as an intra-unit cell (or q=0) magnetism, interpreted in terms of loop current patterns [1], preserving lattice translation (LT) and breaking time-reversal...
The overlay of graphene monolayers with a relative twist has experimentally led to a plethora of correlated physics: superconductivity, correlated insulating phases, nematicity, integer and fractional Chern insulators, spontaneous flavor and magnetic polarization, orbital ferromagnetism or strange-metal behavior. All these phenomena originate from the strong band structure remodeling due to...
Two-dimensional superconductors confront physicists with new challenges by exhibiting a wide variety of unconventional behaviors not captured by the BCS theory. In particular, two-dimensional superconductors are expected to show signs of the Berezinksi-Kosterlitz-Thouless transition (BKT) in their superconducting properties such as resistivity and superfluid stiffness. The cuprate family...
Misfit layer compounds are heterostructures composed of bilayer rocksalts stacked with few layers transition metal dichalcogenides. They host Ising superconductivity, charge density waves and good thermoelectricity. The design of misfits emergent properties is, however, hindered by the lack of a global understanding of the electronic transfer among the constituents. Here, by performing first...
