Home

Person

Helmuth Berger

This person is no longer with EPFL

About
Privacy
Disclaimer

Graph Chatbot

Related publications (311)

Anisotropic spin-flip-induced multiferroic behavior in kagome Cu3Bi(SeO3)(2)O2Cl

Helmuth Berger

Compared to the previous report on Cu3Bi(SeO3)(2)O2X (X = Cl, Br) [V. Gnezdilov et al., (arXiv: 1604.04249)], where no dielectric anomaly was observed without magnetic field near T-N similar to 25.6K, we further present the dielectric behaviors without and ...

Amer Physical Soc2017

Low spin wave damping in the insulating chiral magnet Cu2OSeO3

Helmuth Berger, Dirk Grundler

Chiral magnets with topologically nontrivial spin order such as Skyrmions have generated enormous interest in both fundamental and applied sciences. We report broadband microwave spectroscopy performed on the insulating chiral ferrimagnet Cu2OSeO3. For the ...

American Institute of Physics2017

Evolution of the Fermi surface of BiTeCl with pressure

Helmuth Berger

We report measurements of Shubnikov-de Haas oscillations in the giant Rashba semiconductor BiTeCl under applied pressures up to similar to 2.5 GPa. We observe two distinct oscillation frequencies, corresponding to the Rashba-split inner and outer Fermi sur ...

Iop Publishing Ltd2017

Anomalous spin dynamics in the coupled spin tetramer system CuSeO3

Helmuth Berger

We report high-field magnetization, high-frequency electron spin resonance (ESR), and Se-77 nuclear magnetic resonance (NMR) measurements on the linear spin tetramer system CuSeO3, consisting of strongly interacting Cu(1) dimers and weakly coupled Cu(2) sp ...

Amer Physical Soc2017

Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength-Dependent Mapping

Helmuth Berger

The band structure of many semiconducting monolayer transition metal dichalcogenides (TMDs) possesses two degenerate valleys with equal and opposite Berry curvature. It has been predicted that, when illuminated with circularly polarized light, interband tr ...

Amer Chemical Soc2017

J1-J2 square lattice antiferromagnetism in the orbitally quenched insulator MoOPO4

Helmuth Berger, László Forró, Arnaud Magrez, Oleg Yazyev, Bálint Náfrádi, Henrik Moodysson Rønnow, Ivica Zivkovic, Peter Babkevich, Lin Yang, Noore Elahi Shaik

We report magnetic and thermodynamic properties of a 4d1 (Mo5+) magnetic insulator MoOPO4 single crystal, which realizes a J1−J2 Heisenberg spin-1/2 model on a stacked square lattice. The specific-heat measurements show a magnetic transition at 16 K which ...

Amer Physical Soc2017

Magnetic and thermodynamic properties of CuxTiSe2 single crystals

Helmuth Berger

We present a detailed study of the phase diagram of copper-intercalated TiSe2 single crystals, combining local Hall-probe magnetometry, tunnel diode oscillator technique (TDO), and specific-heat and angle-resolved photoemission spectroscopy measurements. A ...

Amer Physical Soc2017

Persistence of a surface state arc in the topologically trivial phase of MoTe2

Helmuth Berger, Philippe Bugnon, Marco Grioni, Arnaud Magrez, Oleg Yazyev, Alberto Crepaldi, Gabriel Albert Autes

The prediction of Weyl fermions in the low-temperature noncentrosymmetric 1T' phase of MoTe2 still awaits clear experimental confirmation. Here, we report angle-resolved photoemission (ARPES) data and ab initio calculations that reveal a surface state arc ...

Amer Physical Soc2017

Local resilience of the 1T-TiSe2 charge density wave to Ti self-doping

Helmuth Berger, Philipp Aebi, Elia Razzoli

In Ti-intercalated self-doped 1T-TiSe2 crystals, the charge density wave (CDW) superstructure induces two nonequivalent sites for Ti dopants. Recently, it has been shown that increasing Ti doping dramatically influences the CDW by breaking it into phase-sh ...

Amer Physical Soc2017

Time-resolved ARPES at LACUS: Band Structure and Ultrafast Electron Dynamics of Solids

Helmuth Berger, Philippe Bugnon, Marco Grioni, Majed Chergui, Frank van Mourik, Arnaud Magrez, Christopher Alexander Arrell, Alberto Crepaldi, José Javier Pancracio Ojeda Andara, Gianmarco Gatti, Silvan Dino Marcos Roth

The manipulation of the electronic properties of solids by light is an exciting goal, which requires knowledge of the electronic structure with energy, momentum and temporal resolution. Time- and angle-resolved photoemission spectroscopy (tr-ARPES) is the ...

2017

Complex magnetic incommensurability and electronic charge transfer through the ferroelectric transition in multiferroic Co3TeO6

Helmuth Berger, Yang Zhao

Polarized and unpolarized neutron diffractions have been carried out to investigate the nature of the magnetic structures and transitions in monoclinic Co3TeO6. As the temperature is lowered below 26 K long range order develops, which is fully incommensura ...

Springer Nature2017

Bulk diffusive relaxation mechanisms in optically excited topological insulators

Helmuth Berger, Philippe Bugnon, Arnaud Magrez, Alberto Crepaldi

The possibility to inject spin currents in topological insulators (TIs) by ultrashort optical pulses has stimulated intense studies of their out-of-equilibrium electronic properties. However, a comprehensive description of the electronic relaxation dynamic ...

Amer Physical Soc2017

Electronic Phase Separation and Dramatic Inverse Band Renormalization in the Mixed-Valence Cuprate LiCu2O2

Helmuth Berger, Philippe Bugnon, Marco Grioni, Arnaud Magrez, Luca Moreschini, Simon Karl Moser, Gianmarco Gatti

We measured, by angle-resolved photoemission spectroscopy, the electronic structure of LiCu2O2, a mixed-valence cuprate where planes of Cu(I) (3d(10)) ions are sandwiched between layers containing one-dimensional edge-sharing Cu(II) (3d(9)) chains. We find ...

Amer Physical Soc2017

Dynamical Defects in Rotating Magnetic Skyrmion Lattices

Helmuth Berger

The chiral magnet Cu2OSeO3 hosts a Skyrmion lattice that may be equivalently described as a superposition of plane waves or a lattice of particlelike topological objects. A thermal gradient may break up the Skyrmion lattice and induce rotating domains, rai ...

Amer Physical Soc2017

Magnetic and dielectric order in the kagomelike francisite Cu3Bi(SeO3)(2)O2Cl

Helmuth Berger

We report a single-crystal neutron diffraction and inelastic neutron scattering study on the spin 1/2 cuprate Cu3Bi(SeO3)(2)O2Cl, complemented by dielectric and electric polarization measurements. The study clarifies a number of open issues concerning this ...

Amer Physical Soc2017

High-energy electronic interaction in the 3d band of high-temperature iron-based superconductors

Helmuth Berger, Maryna Viazovska

One of the most unique and robust experimental facts about iron-based superconductors is the renormalization of the electronic band dispersion by factor of 3 and more near the Fermi level. Obviously related to the electron pairing, this prominent deviation ...

2017

Ising pairing in superconducting NbSe2 atomic layers

Helmuth Berger, László Forró

The properties of two-dimensional transition metal dichalcogenides arising from strong spin-orbit interactions and valley-dependent Berry curvature effects have recently attracted considerable interest(1-7). Although single-particle and excitonic phenomena ...

Nature Publishing Group2016

Gate Tuning of Electronic Phase Transitions in Two-Dimensional NbSe2

Helmuth Berger, László Forró

Recent experimental advances in atomically thin transition metal dichalcogenide (TMD) metals have unveiled a range of interesting phenomena including the coexistence of charge-density-wave (CDW) order and superconductivity down to the monolayer limit. The ...

Amer Physical Soc2016

Evidence for a Strong Topological Insulator Phase in ZrTe5

Helmuth Berger, Philippe Bugnon, Arnaud Magrez, Oleg Yazyev, Alberto Crepaldi, Luca Gragnaniello, Gabriel Albert Autes

The complex electronic properties of ZrTe5 have recently stimulated in-depth investigations that assigned this material to either a topological insulator or a 3D Dirac semimetal phase. Here we report a comprehensive experimental and theoretical study of bo ...

Amer Physical Soc2016

Probing the coupling between a doublon excitation and the charge-density wave in TaS2 by ultrafast optical spectroscopy

Helmuth Berger, Arnaud Magrez, Ahmad Odeh, Fabrizio Carbone, Andreas Helmut Christian Mann, Edoardo Baldini

Recently, the switching between the different charge-ordered phases of 1T-TaS2 has been probed by ultrafast techniques, revealing unexpected phenomena such as "hidden" metastable states and peculiar photoexcited charge patterns. Here, we apply broadband pu ...

Amer Physical Soc2016

Page 5 of 16