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Helmuth Berger

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Related publications (298)

Page 5 of 15

Spin-stripe phase in a frustrated zigzag spin-1/2 chain

Helmuth Berger

Motifs of periodic modulations are encountered in a variety of natural systems, where at least two rival states are present. In strongly correlated electron systems, such behaviour has typically been associated with competition between short-and long-range ...

Nature Publishing Group2015

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

Dimensional Crossover in a Charge Density Wave Material Probed by Angle-Resolved Photoemission Spectroscopy

Matthias Wolf, Helmuth Berger, Christophe Berthod

High-resolution angle-resolved photoemission spectroscopy data reveal evidence of a crossover from one-dimensional (1D) to three-dimensional (3D) behavior in the prototypical charge density wave (CDW) material NbSe3. In the low-temperature 3D regime, gaps ...

Amer Physical Soc2017

Dynamics of charge density wave order in the quasi one dimensional conductor (TaSe4)(2)I probed by femtosecond optical spectroscopy

Helmuth Berger

Carrier and collective mode dynamics in the quasi one-dimensional charge density wave (CDW) system (TaSe4)(2)I have been investigated by means of time-resolved optical pump-probe spectroscopy. In the low excitation, linear, regime we focus on the temperatu ...

Springer Heidelberg2013

Interplay between the magnetic and electric degrees of freedom in multiferroic Co3TeO6

Helmuth Berger, Yang Zhao

Neutron diffraction, magnetic susceptibility, specific heat, and dielectric constant measurements of single-crystal Co3TeO6 have been measured to study the interplay between the ferroelectricity and magnetic order. Long-range incommensurate magnetic order ...

2012

Magnetic phase diagram of the multiferroic FeTe2O5Br

Helmuth Berger

The low-temperature magnetic phase diagram of the multiferroic system FeTe2O5Br down to 300 mK and up to 9 T is presented. Short-range magnetic correlations within the crystal layers start to develop already at similar to 50 K, i.e., far above T-N1 similar ...

2010

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

Separation of the Oxide and Halide Part in the Oxohalide Fe3Te3O10Cl Due to High Lewis Acidity of the Cations

Helmuth Berger, Dong Zhang

A new iron tellurite halide Fe3Te3O10Cl has been identified that crystallizes in the monoclinic space group P2(1)/c. The crystal structure comprises channels where the Cl ions and also the stereochemically active lone-pair electrons on Te4+ are located. Th ...

2009

Frictional Characteristics of Atomically Thin Sheets

Helmuth Berger

Using friction force microscopy, we compared the nanoscale frictional characteristics of atomically thin sheets of graphene, molybdenum disulfide (MoS2), niobium diselenide, and hexagonal boron nitride exfoliated onto a weakly adherent substrate (silicon o ...

American Association for the Advancement of Science2010

Magnetoelectricity in the ferrimagnetic Cu2OSeO3: symmetry analysis and Raman scattering study

Helmuth Berger

sublattices ferrimagnet Cu2OSeO3 with a cubic symmetry and a linear magnetoelectric effect. There is no spectroscopic evidence for structural lattice distortions below T-C=60 K, which are expected due to magnetoelectric coupling. Using symmetry arguments w ...

2010

Insight into the electronic structure of semiconducting epsilon-GaSe and epsilon-InSe

Helmuth Berger, Marco Grioni, Alberto Crepaldi

Metal monochalcogenides (MX) have recently been rediscovered as two-dimensional materials with electronic properties highly dependent on the number of layers. Although some intriguing properties appear in the few-layer regime, the carrier mobility of MX co ...

AMER PHYSICAL SOC2020

Unexpected observation of splitting of skyrmion phase in Zn doped Cu2OSeO3

Helmuth Berger

Polycrystalline (Cu1-xZnx)(2)OSeO3 (0

Nature Publishing Group2015

van der Waals pi Josephson Junctions

László Forró, Helmuth Berger

Proximity-induced superconductivity in a ferromagnet can induce Cooper pairs with a finite center-of-mass momentum and stabilize Josephson junctions (JJs) with pi phase difference in superconductor-ferromagnet-superconductor heterostructures. The emergence ...

AMER CHEMICAL SOC2022

Coexisting spinons and magnons in the frustrated zigzag spin-1/2 chain compound beta-TeVO4

Helmuth Berger

We investigate magnetic excitations in the frustrated zigzag spin-1/2 chain compound beta-TeVO4 by inelastic neutron scattering. In the magnetically ordered ground state, the excitation spectrum exhibits coexisting magnon dispersion, characteristic of long ...

AMER PHYSICAL SOC2018

High-Pressure Phase Transitions and Structures of Topological Insulator BiTel

Helmuth Berger

Being a giant bulk Rashba semiconductor, the ambient-pressure phase of BiTeI was predicted to transform into a topological insulator under pressure at 1.7-4.1 GPa [Nat. Commun. 2012, 3, 679]. Because the structure governs the new quantum state of matter, i ...

Amer Chemical Soc2013

Microwave absorption in the frustrated ferrimagnet Cu2OSeO3

Helmuth Berger

The resonance properties of a new Cu2OSeO3 ferrimagnet have been investigated in a wide range of frequencies (17-142 GHz) at liquid helium temperature. The resonance data were used to plot the frequency-field curve of the ferromagnetic spectrum described i ...

2010

Magnetic order and low-energy excitations in the quasi-one-dimensional antiferromagnet CuSe2O5 with staggered fields

Helmuth Berger

Ground-state and low-energy excitations of the quasi-one-dimensional antiferromagnet CuSe2O5 where finite interchain interactions promote long-range antiferromagnetic order below T-N = 17 K, were experimentally studied using bulk magnetization, neutron dif ...

Amer Physical Soc2013

Linearly polarized GHz magnetization dynamics of spin helix modes in the ferrimagnetic insulator Cu_2OSeO_3

Dirk Grundler, Helmuth Berger

Linear dichroism — the polarization dependent absorption of electromagnetic waves— is routinely exploited in applications as diverse as structure determination of DNA or polarization filters in optical technologies. Here filamentary absorbers with a large ...

Nature Research2017

Ising pairing in superconducting NbSe2 atomic layers

László Forró, Helmuth Berger

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

Slow magnetic dynamics and hysteresis loops of the bulk ferromagnet Co-7(TeO3)(4)Br-6

Helmuth Berger, Ivica Zivkovic

Magnetic dynamics of a bulk ferromagnet, a new single crystalline compound Co-7(TeO3)(4)Br-6, was studied by ac susceptibility and related techniques. Very large Arrhenius activation energy of 17.2 meV (201 K) and long attempt time (2 x 10(-4) s) span the ...

2011