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Helmuth Berger

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Related publications (311)

Scattering-dominated high-temperature phase of 1T-TiSe2: An optical conductivity study

Helmuth Berger, László Forró, Eduard Tutis, Neven Barisic

The controversy regarding the precise nature of the high-temperature phase of 1T-TiSe2 lasts for decades. It has intensified in recent times when new evidence for the excitonic origin of the low-temperature charge-density wave state started to unveil. Here ...

Amer Physical Soc2016

Anisotropic transport properties of tungsten disulfide

Helmuth Berger, László Forró, Richard Gaal, Bálint Náfrádi, Jacim Jacimovic, Andrea Pisoni

Single crystals of WS2 were prepared by chemical vapor transport method using sulfur as a transport agent. Measurements of electrical resistivity, Seebeck coefficient and thermal conductivity as a function of temperature, along the in-plane and the out-of- ...

Pergamon-Elsevier Science Ltd2016

Evolution of the charge density wave superstructure in ZrTe3 under pressure

Helmuth Berger, Philipp Aebi, Corsin Battaglia

The material ZrTe3 is a well-known example of an incommensurate periodic lattice distortion (PLD) at low temperatures due to a charge density wave (CDW). Previous studies have found a sharp boundary as a function of pressure between CDW below 5 GPa and bul ...

Amer Physical Soc2016

Advancing non-equilibrium ARPES experiments by a 9.3 eV coherent ultrafast photon source

Helmuth Berger, Philippe Bugnon, Alberto Crepaldi

The quest for investigating the non-equilibrium dynamics of the band structure of strongly-correlated materials over their entire Brillouin zone is a primary objective. However, the actual ultrafast UV light sources are not suitable for addressing several ...

Elsevier Science Bv2016

Exchange anisotropy as mechanism for spin-stripe formation in frustrated spin chains

Helmuth Berger

We investigate the spin-stripe mechanism responsible for the peculiar nanometer modulation of the incommensurate magnetic order that emerges between the vector-chiral and the spin-density-wave phase in the frustrated zigzag spin-1/2 chain compound beta-TeV ...

Amer Physical Soc2016

Dramatic pressure-driven enhancement of bulk skyrmion stability

Helmuth Berger, Arnaud Magrez, Henrik Moodysson Rønnow, Ivica Zivkovic, Jonathan White, Oleksandr Kriuchkov

The recent discovery of magnetic skyrmion lattices initiated a surge of interest in the scientific community. Several novel phenomena have been shown to emerge from the interaction of conducting electrons with the skyrmion lattice, such as a topological Ha ...

Nature Research2016

Resonant elastic x-ray scattering from the skyrmion lattice in Cu2OSeO3

Helmuth Berger

We report the study of the skyrmion state near the surface of Cu2OSeO3 using soft resonant elastic x-ray scattering (REXS) at the Cu L-3 edge. Within the lateral sampling area of 200 x 200 mu m(2), we found a long-range-ordered skyrmion lattice phase as we ...

Amer Physical Soc2016

Multidomain Skyrmion Lattice State in Cu2OSeO3

Helmuth Berger

Magnetic skyrmions in chiral magnets are nanoscale, topologically protected magnetization swirls that are promising candidates for spintronics memory carriers. Therefore, observing and manipulating the skyrmion state on the surface level of the materials a ...

Amer Chemical Soc2016

Experimental determination of the bulk Rashba parameters in BiTeBr

Helmuth Berger, Philippe Bugnon, Arnaud Magrez

Shubnikov-de Haas (SdH) oscillations, Hall effect, and optical reflectance (R(omega)) measurements have been performed on single crystals of BiTeBr. Under magnetic fields up to 32 tesla and at temperatures as low as 0.4K, the SdH data shows a single oscill ...

IOP Publishing - EPL Association2016

Short-range phase coherence and origin of the 1T-TiSe2 charge density wave

Helmuth Berger, Philipp Aebi, Elia Razzoli

The impact of variable Ti self-doping on the 1T-TiSe2 charge density wave (CDW) is studied by scanning tunneling microscopy. Supported by density functional theory, we show that agglomeration of intercalated-Ti atoms acts as preferential nucleation centers ...

Amer Physical Soc2016

Revealing the role of electrons and phonons in the ultrafast recovery of charge density wave correlations in 1T-TiSe2

Helmuth Berger, Arnaud Magrez, Matthias Wolf

Using time-and angle-resolved photoemission spectroscopy with selective near-and midinfrared photon excitations, we investigate the femtosecond dynamics of the charge density wave ( CDW) phase in 1T-TiSe2 as well as the dynamics of CDW fluctuations at 240 ...

Amer Physical Soc2016

Origin and Magnitude of 'Designer' Spin-Orbit Interaction in Graphene on Semiconducting Transition Metal Dichalcogenides

Helmuth Berger, Zhe Wang

We use a combination of experimental techniques to demonstrate a general occurrence of spin-orbit interaction (SOI) in graphene on transition metal dichalcogenide (TMD) substrates. Our measurements indicate that SOI is ultrastrong and extremely robust, des ...

American Physical Society2016

Magnetic anisotropy in the frustrated spin-chain compound beta-TeVO4

Helmuth Berger

Isotropic and anisotropic magnetic behavior of the frustrated spin-chain compound beta-TeVO4 is reported. Three magnetic transitions observed in zero magnetic field are tracked in fields applied along different crystallographic directions using magnetizati ...

Amer Physical Soc2016

Gate-induced superconductivity in atomically thin MoS2 crystals

Helmuth Berger

When thinned down to the atomic scale, many layered van der Waals materials exhibit an interesting evolution of their electronic properties, whose main aspects can be accounted for by changes in the single-particle bandstructure. Phenomena driven by intera ...

Nature Publishing Group2016

Nature and topology of the low-energy states in ZrTe5

Helmuth Berger, Marco Grioni, Luca Moreschini, Jens Christian Johannsen

Long known for its peculiar resistivity, showing a thus far unexplained anomalous peak as a function of temperature, ZrTe5 has recently received rising attention in a somewhat different context. While both theoretical and experimental results seem to point ...

Amer Physical Soc2016

Negative plasmon dispersion in 2H-NbS2 beyond the charge-density-wave interpretation

Helmuth Berger

We examine the experimental and theoretical electron-energy loss spectra in 2H-Cu0.2NbS2 and find that the 1 eV plasmon in this material does not exhibit the regular positive quadratic plasmon dispersion that would be expected for a normal broad-parabolic- ...

Iop Publishing Ltd2016

Doping dependent plasmon dispersion in 2H-transition metal dichalcogenides

Helmuth Berger

We report the behavior of the charge carrier plasmon of 2H-transition metal dichalcogenides (TMDs) as a function of intercalation with alkali metals. Intercalation and concurrent doping of the TMD layers have a substantial impact on plasmon energy and disp ...

Amer Physical Soc2016

Electrical resistance of single-crystal magnetite (Fe3O4) under quasi-hydrostatic pressures up to 100GPa

Helmuth Berger

The pressure dependence of electrical resistance of single-crystal magnetite (Fe3O4) was measured under quasi-hydrostatic conditions to 100 GPa using low-temperature, megabar diamond-anvil cell techniques in order to gain insight into the anomalous behavio ...

Amer Inst Physics2016

Heuristic Description of Magnetoelectricity of Cu2OSeO3

Helmuth Berger

CuO2SeO3 is an insulating material that hosts topologically nontrivial spin whirls, so-called skyrmions, and exhibits magnetoelectric coupling allowing to manipulate these skyrmions by means of electric fields. We report magnetic force microscopy imaging o ...

Amer Chemical Soc2016

Imaging and manipulation of skyrmion lattice domains in Cu2OSeO3

Helmuth Berger

Nanoscale chiral skyrmions in noncentrosymmetric helimagnets are promising binary state variables in high-density, low-energy nonvolatile memory. Skyrmions are ubiquitous as an ordered, single-domain lattice phase, which makes it difficult to write informa ...

Amer Inst Physics2016

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