Publications de Helmuth Berger

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Ionic liquid gated field-effect transistors (FETs) based on semiconducting transition metal dichalcogenides (TMDs) are used to study a rich variety of extremely interesting physical phenomena, but important aspects of how charge carriers are accumulated in ...

Co1/3NbS2 is the magnetic intercalate of 2H-NbS2 where electronic itinerant and magnetic properties strongly influence each other throughout the phase diagram. Here we report the angle-resolved photoelectron spectroscopy (ARPES) study in Co1/3NbS2. In agre ...

We report a combined experimental and theoretical investigation that reveals a new mechanism responsible for the enhancement of electron-phonon coupling in doped semiconductors in which multiple inequivalent valleys are simultaneously populated. Using Rama ...

Crystalline defects can modify quantum interactions in solids, causing unintuitive, even favourable, properties such as quantum Hall effect or superconducting vortex pinning. Here we present another example of this notion-an unexpected unidirectional Kondo ...

Optical second-harmonic generation (SHG) can only occur in noncentrosymmetric crystals in the leading electric-dipole approximation. Transition metal dichalcogenides with the 1T octahedral coordination is centrosymmetric, hence precluding SHG. Here we repo ...

Transition-metal dichalcogenides (TMDs) are layered compounds that support many electronic phases, including various charge density waves, superconducting, and Mott insulating states. Their intercalation with magnetic ions introduces magnetic sublayers, wh ...

Neutron scattering studies on powder and single crystals have provided new evidence for unconventional magnetism in Cu2Te2O5Cl2. The compound is built from tetrahedral clusters of S=1/2 Cu2+ spins located on a tetragonal lattice. Magnetic ordering, emergin ...

The discovery of the anomalous Hall effect (AHE) in bulk metallic antiferromagnets (AFMs) motivates the search of the same phenomenon in two-dimensional (2D) systems, where a quantized anomalous Hall conductance can, in principle, be observed. Here we pres ...

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 ...

Precision measurements of the magnetization and ac susceptibility of Cu2OSeO3 are reported for magnetic fields along different crystallographic directions, focusing on the border between the conical and the field-polarized state for a magnetic field along ...

The effects of external (hydrostatic) compression and internal (chemical) expansion on the skyrmion phase have been investigated in Cu2OSeO3 single crystal and Cu2OSe1-xTexO3 (0

We report powder and single-crystal neutron diffractionmeasurements, combinedwith x-ray powder diffraction data, to unravel the complex magnetic phase diagram and exchange coupling in Co3TeO6. The magnetic structures of the various phases differ markedly f ...

Bulk Rashba systems BiTeX (X = I, Br, Cl) are emerging as important candidates for developing spintronics devices because of the coexistence of spin-split bulk and surface states, along with the ambipolar character of the surface charge carriers. The need ...

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 ...

Magnetic materials can host skyrmions, which are topologically non-trivial spin textures. In chiral magnets with cubic lattice symmetry, all previously observed skyrmion phases require thermal fluctuations to become thermodynamically stable in bulk materia ...

We report measurements of Shubnikov-de Haas oscillations in the giant Rashba semiconductor BiTeI under applied pressures up to similar to 2GPa. We observe one high frequency oscillation at all pressures and one low frequency oscillation that emerges betwee ...

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 ...

Recent technical progress demonstrates the possibility of stacking together virtually any combination of atomically thin crystals of van der Waals bonded compounds to form new types of heterostructures and interfaces. As a result, there is the need to unde ...

2H-NbSe2 is a prototypical charge-density-wave (CDW) system, exhibiting such a symmetry-breaking quantum ground state in its bulk and down to a single-atomic-layer limit. However, how this state depends on dimensionality and what governs the dimensionality ...

We present an experimental study of macroscopic and microscopic magnetic anisotropy of a spin tetramer system SeCuO3 using torque magnetometry and ESR spectroscopy. Large rotation of macroscopic magnetic axes with temperature observed from torque magnetome ...

Helmuth Berger

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Band Filling and Cross Quantum Capacitance in Ion-Gated Semiconducting Transition Metal Dichalcogenide Monolayers

Role of intercalated cobalt in the electronic structure of Co1/3NbS2

Enhanced Electron-Phonon Interaction in Multivalley Materials

Unidirectional Kondo scattering in layered NbS2

Second-harmonic generation in atomically thin 1T-TiSe2 and its possible origin from charge density wave transitions

Electronic transport and magnetism in the alternating stack of metallic and highly frustrated magnetic layers in Co(1/3)NbS(2)

Incommensurate magnetism in the coupled spin tetrahedra system Cu2Te2O5Cl2

Giant anomalous Hall effect in quasi-two-dimensional layered antiferromagnet Co1/3NbS2

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

Thermodynamic evidence of a second skyrmion lattice phase and tilted conical phase in Cu2OSeO3

Physical pressure and chemical expansion effects on the skyrmion phase in Cu2OSeO3

Complex magnetic couplings in Co3TeO6

Momentum and photon energy dependence of the circular dichroic photoemission in the bulk Rashba semiconductors BiTeX (X = I, Br, Cl)

Bulk diffusive relaxation mechanisms in optically excited topological insulators

Observation of two independent skyrmion phases in a chiral magnetic material

Pressure tuning the Fermi level through the Dirac point of giant Rashba semiconductor BiTeI

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

Semiconducting van der Waals Interfaces as Artificial Semiconductors

Axial-Bonding-Driven Dimensionality Effect on the Charge-Density Wave in NbSe2

Magnetic anisotropy of the spin tetramer system SeCuO3 studied by torque magnetometry and ESR spectroscopy