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Publications associées (20)

Weyl metallic state induced by helical magnetic order

Henrik Moodysson Rønnow, Ivica Zivkovic, Jan Hugo Dil, Jian Rui Soh, Xupeng Yang

In the rapidly expanding field of topological materials there is growing interest in systems whose topological electronic band features can be induced or controlled by magnetism. Magnetic Weyl semimetals, which contain linear band crossings near the Fermi ...

Nature Portfolio2024

Nonlinear optical diode effect in a magnetic Weyl semimetal

Philip Johannes Walter Moll, Chunyu Guo, Hao Yang

Diode effects are of great interest for both fundamental physics and modern technologies. Electrical diode effects (nonreciprocal transport) have been observed in Weyl systems. Optical diode effects arising from the Weyl fermions have been theoretically co ...

Nature Portfolio2024

Strain Gradients and Magnetoresistance in Microstructured 3D Topological Semi-metals

Jonas De Jesus Diaz Gomez

Three-dimensional topological semimetals have emerged as strong candidates to probe new fundamental physical phenomena that could be exploited to develop next generation electronics. However, many aspects of their electronic properties remain unclear. Thi ...

EPFL2023

Addressing shape and extent of Weyl cones in TaAs by Landau level spectroscopy

Ana Akrap

TaAs is a prime example of a topological semimetal with two types of Weyl nodes, W-1 and W-2, whose bulk signatures have proven elusive. We apply Landau level spectroscopy to crystals with multiple facets and identify-among other low-energy excitations bet ...

AMER PHYSICAL SOC2022

On complete reducibility of tensor products of simple modules over simple algebraic groups

Jonathan Gruber

Let G be a simply connected simple algebraic group over an al- gebraically closed ﬁeld k of characteristic p > 0. The category of rationalG-modules is not semisimple. We consider the question of when the tensorproduct of two simple G-modules L(λ) and L(μ) ...

2021

Optical conductivity of the type-II Weyl semimetal TaIrTe4

Ana Akrap, Konstantin Semeniuk

TaIrTe4 is an example of a candidate Weyl type-II semimetal with a minimal possible number of Weyl nodes. Four nodes are reported to exist in a single plane in k space. The existence of a conical dispersion linked toWeyl nodes has yet to be shown experimen ...

AMER PHYSICAL SOC2020

Orbital effect and weak localization in the longitudinal magnetoresistance of Weyl semimetals NbP, NbAs, TaP, and TaAs

Philip Johannes Walter Moll, Maja Deborah Bachmann

Weyl semimetals such as the TaAs family (TaAs, TaP, NbAs, NbP) host quasiparticle excitations resemblingthe long-sought-after Weyl fermions at special band-crossing points in the band structure denoted as Weylnodes. They are predicted to exhibit a negative ...

2020

Examples of algebraic groups of type G (2) having the same maximal tori

Ting-Yu Lee

Answering a question of A. Rapinchuk, we construct examples of non-isomorphic semisimple algebraic groups H (1) and H (2) of type G (2) having coherently equivalent systems of maximal k-tori. ...

Maik Nauka/Interperiodica/Springer2016

Observation of Weyl nodes and Fermi arcs in tantalum phosphide

Oleg Yazyev, Joël Mesot, Gabriel Albert Autes, Kazimierz Conder

A Weyl semimetal possesses spin-polarized band-crossings, called Weyl nodes, connected by topological surface arcs. The low-energy excitations near the crossing points behave the same as massless Weyl fermions, leading to exotic properties like chiral anom ...

Nature Publishing Group2016

The xi-stability on the affine grassmannian

Zongbin Chen

We introduce a notion of xi-stability on the affine grassmannian (SIC) for the classical groups, this is the local version of the xi-stability on the moduli space of Higgs bundles on a curve introduced by Chaudouard and Laumon. We prove that the quotient ( ...

Springer Heidelberg2015

Restricting representations of classical algebraic groups to maximal subgroups

Mikaël Cavallin

Fix an algebraically closed field

K

having characteristic

p\geq 0

and let

Y

be a simple algebraic group of classical type over

K.

Also let

X

be maximal among closed connected subgroups of

Y

and consider a non-trivial

p

-restricted irreducible ...

EPFL2015

Embedding functor for classical groups and Brauer–Manin obstruction

Eva Bayer Fluckiger, Ting-Yu Lee

Let K be a global field of characteristic not 2. The embedding problem for maximal tori in a classical group G can be described in terms of algebras with involution. The aim of this paper is to give an explicit description of the obstruction group to the H ...

2015

Observation of Weyl nodes in TaAs

Joël Mesot

In 1929, H. Weyl proposed that the massless solution of the Dirac equation represents a pair of a new type of particles, the so-called Weyl fermions1. However, their existence in particle physics remains elusive after more than eight decades. Recently, sig ...

Nature Publishing Group2015

Observation of Fermi-Arc Spin Texture in TaAs

Jan Hugo Dil, Joël Mesot, Stefan Peter Muff

We have investigated the spin texture of surface Fermi arcs in the recently discovered Weyl semimetal TaAs using spin- and angle-resolved photoemission spectroscopy. The experimental results demonstrate that the Fermi arcs are spin polarized. The measured ...

American Physical Society2015

Embeddings Of Maximal Tori In Orthogonal Groups

Eva Bayer Fluckiger

We give necessary and sufficient conditions for an orthogonal group defined over a global field of characteristic not equal 2 to contain a maximal torus of a given type. ...

Annales Inst Fourier2014

Sequences with Minimal Time-Frequency Spreads

Martin Vetterli, Reza Parhizkar, Yann Barbotin

For a given time or frequency spread, one can always find continuous- time signals, which achieve the Heisenberg uncertainty principle bound. This is known, however, not to be the case for discrete-time sequences; only widely spread sequences asymptoticall ...

Ieee2013

Stability of Equilibria for the so(4) Free Rigid Body

Tudor Ratiu, Murat Turhan

The stability for all generic equilibria of the Lie-Poisson dynamics of the so(4) rigid body dynamics is completely determined. It is shown that for the generalized rigid body certain Cartan subalgebras (called of coordinate type) of so(n) are equilibrium ...

2012

Minimum euclidien des ordres maximaux dans les algèbres centrales à division

Jérôme Chaubert

This work concerns the study of Euclidean minima of maximal orders in central simple algebras. In the first part, we define the concept of ideal lattice in the non-commutative case. Let A be a semi-simple algebra over Q. An ideal lattice over A is a triple ...

EPFL2007

Symmetry breaking in mechanical systems

The first part of this thesis studies the problem of symmetry breaking in the context of simple mechanical systems with compact symmetry Lie group G. In this part we shall assume that the principal stratum of the G-action on the configuration space Q of a ...

EPFL2005

Système de poids sur une algèbre de Lie nilpotente

Let g be a nilpotent Lie algebra (of finite dimension n over an algebraically closed field of characteristic zero) and let Der(g) be the algebra of derivations of g. The system of weights of g is defined as being that of the standard representation of a "m ...

s.n.1973