• Séminaire théorie
• Personne à contacter : Serge Florens ()
• Lieu : Amphithéâtre, maison des Magistères

Résumé : We theoretically demonstrate that the chiral structure of the nodes of nodal semimetals is responsible for the existence and universal local properties of the edge states in the vicinity of the nodes. We perform a general analysis of the edge states for an isolated node of a 2D semimetal, protected by chiral symmetry and characterized by the topological winding number N. We derive the asymptotic chiral-symmetric boundary conditions and find that there are N+1 universal discrete classes of them. The class determines the numbers of flat-band edge states on either side off the node in the 1D spectrum and the winding number N gives the total number of edge states. We then show that the edge states of chiral nodal semimetals are robust: they persist in a finite-size stability region of parameters of chiral-asymmetric terms. This significantly extends the notion of 2D and 3D topological nodal semimetals. We demonstrate that the Luttinger model with a quadratic-node for j=3/2 electrons (Luttinger semimetal) is a 3D topological semimetal in this new sense and predict that alpha-Sn, HgTe, possibly Pr2Ir2O7, and many other semimetals described by it are topological and exhibit surface state. Reference: M. Kharitonov, J.-B. Mayer, and E. M. Hankiewicz, Phys. Rev. Lett. 119, 266402 (2017).

• Séminaire théorie
• Personne à contacter : Serge Florens ()
• Lieu : Amphithéâtre, maison des Magistères

Résumé : Quantum spin liquids (QSLs) are long-range entangled states of matter with emergent gauge fields and fractionalized excitations. In my talk I will focus on how to search for fractionalized excitations in Kitaev materials, which believe to harbor a variety of QSLs. These Kitaev QSLs exhibit two types of fractionalized quasiparticle excitations - itinerant Majorana fermions and gapped Z2 fluxes. In recent years, a remarkable theoretical and experimental progress has been achieved in understanding that these fractionalized quasiparticles and, in particular, Majorana fermions can be effectively probed by conventional spectroscopic techniques such as inelastic neutron scattering, Raman scattering with visible light, and resonant inelastic X-ray scattering. Another promising direction is to look for experimental signatures of fractionalized quasiparticles in phonon spectra.

Liens :[Natasha Perkins]

• Séminaire théorie
• Personne à contacter :
• Lieu : Amphithéâtre, maison des Magistères

Liens :[Philippe Jacquod]