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Helmuth Berger

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Related publications (311)

Tailoring thermal conduction in anatase TiO2

Luca Rossi, Helmuth Berger, László Forró, Jacim Jacimovic, Endre Horvath, Xavier François Mettan, Andrea Pisoni, Péter Szirmai

Thermal conductivity (κ) plays an essential role in functional devices. It is advantageous to design materials where one can tune κ in a wide range according to its function: single-crystals and nanowires of anatase polymorph of titanium dioxide, broadly u ...

Springer2019

Antiferroelectric antiferromagnetic type-I multiferroic Cu9O2(SeO3)(4)Cl-6

Helmuth Berger, Wei Li

We report that Cu9O2(SeO3)(4)Cl-6 is a new multiferroic compound. Comprehensive studies of this compound have been carried out on single crystals as well as polycrystalline samples. Magnetic susceptibility chi and specific heat C with H parallel to c axis ...

AMER PHYSICAL SOC2019

Magnetic ground state of the frustrated spin-1/2 chain compound beta-TeVO4 at high magnetic fields

Helmuth Berger, Jonathan White

Frustrated spin-1/2 chains, despite the apparent simplicity, exhibit a remarkably rich phase diagram comprising vector-chiral (VC), spin-density-wave (SDW), and multipolar/spin-nematic phases as a function of the magnetic field. Here we report a study of b ...

2019

Two-Dimensional Conical Dispersion in ZrTe5 Evidenced by Optical Spectroscopy

Helmuth Berger, Ana Akrap, Edoardo Martino

Zirconium pentatelluride was recently reported to be a 3D Dirac semimetal, with a single conical band, located at the center of the Brillouin zone. The cone's lack of protection by the lattice symmetry immediately sparked vast discussions about the size an ...

AMER PHYSICAL SOC2019

Strong decoupling between magnetic subsystems in the low-dimensional spin-1/2 antiferromagnet SeCuO3

Helmuth Berger

The search for and understanding of low-dimensional magnetic materials is essential for both fundamental and technological purposes. Here we propose a combined experimental and theoretical investigation of such a system, namely the monoclinic phase of SeCu ...

2019

Observation of charge-transfer-driven antiferroelectricity in 3d-pyrochlore multiferroic Cu2OCl2

Helmuth Berger, Wei Li

Very recently, multiferroic behavior close to the boiling temperature of liquid nitrogen was reported in oxohalide-based Cu2OCl2. In this study, we have established yet another novel mechanism for the origin of charge ordering in multiferroic Cu2OCl2. The ...

ELSEVIER SCIENCE BV2019

Phonon origin and lattice evolution in charge density wave states

Helmuth Berger

Metallic transition metal dichalcogenides, such as tantalum diselenide (TaSe2), display quantum correlated phenomena of superconductivity and charge density waves (CDWs) at low temperatures. Here, the photophysics of 2H-TaSe2 during CDW transitions is reve ...

AMER PHYSICAL SOC2019

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

Christophe Berthod, Helmuth Berger, Thierry Giamarchi, Haijing Zhang

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 ...

2019

Enhanced Electron-Phonon Interaction in Multivalley Materials

Helmuth Berger, Nicola Marzari, Evgeniy Ponomarev, Marco Gibertini, Thibault Daniel Pierre Sohier

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 ...

American Physical Society2019

Large magnetothermopower and anomalous Nernst effect in HfTe5

Jean-Philippe Ansermet, Helmuth Berger, Arnaud Magrez, Haiming Yu, Jan Hugo Dil, Edoardo Martino, Sa Tu, Marco Caputo, Junfeng Hu

Topological quantum materials have stimulated growing attention because they reveal novel aspects of condensed matter physics and point to new opportunities in materials science, in particular for thermoelectrics. Here, we experimentally study thermoelectr ...

AMER PHYSICAL SOC2019

Polarization dependence of angle-resolved photoemission with submicron spatial resolution reveals emerging one-dimensionality of electrons in NbSe3

Helmuth Berger, Marco Grioni, Emmanouil Frantzeskakis, Miguel Angel Valbuena

In materials with nearly commensurate band filling the electron liquid may spontaneously separate into components with distinct properties, yielding complex intra- and interunit cell ordering patterns and a reduced dimensionality. Polarization-dependent an ...

AMER PHYSICAL SOC2019

Soft-phonon driven hexagonal-orthorhombic phase transition in BaVS3

Helmuth Berger

The lattice dynamics of low-dimensional BaVS3 is reported across the hexagonal-orthorhombic phase transition occurring at T-S = 250 K using a combination of the thermal diffuse scattering of x rays, inelastic x-ray scattering, and density functional theory ...

2019

Elementary excitation in the spin-stripe phase in quantum chains

Helmuth Berger, Jonathan White

Elementary excitations in condensed matter capture the complex many-body dynamics of interacting basic entities in a simple quasiparticle picture. In magnetic systems the most established quasiparticles are magnons, collective excitations that reside in or ...

Springer2019

The influence of the incommensurately modulated structure on the physical properties of Fe1.35Ge

Helmuth Berger, László Forró, Alla Arakcheeva, Philip Pattison, Krunoslav Prsa, Jacim Jacimovic, Sergiy Katrych, Andrea Pisoni

Single crystal growth by chemical vapour transport has resulted samples with Fe1.35Ge stoichiometry. Structural study has shown that the large number of vacancies introduces an incommensuately modulated structure. The electrical resistivity is in the 200 m ...

2019

Singlet state formation and its impact on the magnetic structure in the tetramer system SeCuO3

Helmuth Berger, Arnaud Magrez, Krunoslav Prsa, Henrik Moodysson Rønnow, Ivica Zivkovic, Peter Babkevich

We present an experimental investigation of the magnetic structure in a tetramer system SeCuO3 using neutron powder-diffraction and nuclear resonance techniques. We establish a commensurate antiferromagnetic ordering with a propagation vector k = (0, 0, 1) ...

2018

Coherent organization of electronic correlations as a mechanism to enhance and stabilize high-T-C cuprate superconductivity

Helmuth Berger

Nature Research2018

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Helmuth Berger

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Tailoring thermal conduction in anatase TiO2

Antiferroelectric antiferromagnetic type-I multiferroic Cu9O2(SeO3)(4)Cl-6

Magnetic ground state of the frustrated spin-1/2 chain compound beta-TeVO4 at high magnetic fields

Two-Dimensional Conical Dispersion in ZrTe5 Evidenced by Optical Spectroscopy

Strong decoupling between magnetic subsystems in the low-dimensional spin-1/2 antiferromagnet SeCuO3

Observation of charge-transfer-driven antiferroelectricity in 3d-pyrochlore multiferroic Cu2OCl2

Phonon origin and lattice evolution in charge density wave states

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

Enhanced Electron-Phonon Interaction in Multivalley Materials

Large magnetothermopower and anomalous Nernst effect in HfTe5

Polarization dependence of angle-resolved photoemission with submicron spatial resolution reveals emerging one-dimensionality of electrons in NbSe3

Soft-phonon driven hexagonal-orthorhombic phase transition in BaVS3

Elementary excitation in the spin-stripe phase in quantum chains

The influence of the incommensurately modulated structure on the physical properties of Fe1.35Ge

Singlet state formation and its impact on the magnetic structure in the tetramer system SeCuO3

Universal scattering response across the type-II Weyl semimetal phase diagram

Evidence of a Coulomb-Interaction-Induced Lifshitz Transition and Robust Hybrid Weyl Semimetal in Td−MoTe2

Spin-Resolved Electronic Response to the Phase Transition in MoTe2

An unusual continuous paramagnetic-limited superconducting phase transition in 2D NbSe2

Coherent organization of electronic correlations as a mechanism to enhance and stabilize high-T-C cuprate superconductivity