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Johan Juul Chang

Cette personne a quitté l’EPFL

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Publications associées (21)

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Glassy low-energy spin fluctuations and anisotropy gap in La1.88Sr0.12CuO4

Henrik Moodysson Rønnow, Joël Mesot, Johan Juul Chang

We present high-resolution triple-axis neutron scattering studies of the high-temperature superconductor La1.88Sr0.12CuO4 (Tc=27 K). The temperature dependence of the low-energy incommensurate magnetic fluctuations reveals distinctly glassy features. The g ...

American Physical Society2013

Search for relativistic fractionally charged particles in space

Jian Wang, Zhirui Xu, Yi Zhang, Yi Wang, Siyuan Wang, Songmei Wu, Junqiu Liu, Johan Juul Chang, Cheng Zhao, Chiara Perrina, Jennifer Maria Frieden

More than a century after the performance of the oil drop experiment, the possible existence of fractionally charged particles (FCPs) still remains unsettled. The search for FCPs is crucial for some extensions of the Standard Model in particle physics. Mos ...

American Physical Society2022

The Fermi surface and band folding in La2-xSrxCuO4, probed by angle-resolved photoemission

Joël Mesot, Johan Juul Chang, Martin Mansson

A systematic angle-resolved photoemission study of the electronic structure of La2-xSrxCuO4 in a wide doping range is presented in this paper. In addition to the main energy band, we observed a weaker additional band, the (pi, pi) folded band, which shows ...

2010

Electronic structure of La1.48Nd0.4Sr0.12CuO4 probed by high- and low-energy angle-resolved photoelectron spectroscopy

Joël Mesot, Martin Mansson, Johan Juul Chang

We present angle-resolved photoelectron spectroscopy data probing the electronic structure of the Nd-substituted high-T-c cuprate La1.48Nd0.4Sr0.12CuO4. Data have been acquired at low and high photon energies, h nu=55 and 500 eV, respectively. The two extr ...

2009

Evolution from a Nodeless Gap to d(x2-y2)-Wave in Underdoped La2-xSrxCuO4

Joël Mesot, Johan Juul Chang

Using angle-resolved photoemission spectroscopy (ARPES), it is revealed that the low-energy electronic excitation spectra of highly underdoped superconducting and nonsuperconducting La2-xSrxCuO4 cuprates are gapped along the entire underlying Fermi surface ...

Amer Physical Soc2013

Decoupling of lattice and orbital degrees of freedom in an iron-pnictide superconductor

Qian Wang, László Forró, Johan Juul Chang, Sergiy Katrych

The interplay between structural and electronic phases in iron-based superconductors is a central theme in the search for the superconducting pairing mechanism. While electronic nematicity is competing with superconductivity, the effect of purely structura ...

AMER PHYSICAL SOC2021

Resonant inelastic x-ray scattering study of Ca3Ru2O7

Qian Wang, Johan Juul Chang, Thorsten Schmitt, Yi Tseng, Claudia Giuseppina Fatuzzo

We present a combined oxygen K-edge x-ray absorption spectroscopy and resonant inelastic x-ray scattering (RIXS) study of the bilayer ruthenate Ca3Ru2O7. Our RIXS experiments on Ca3Ru2O7 were carried out on the overlapping planar and interplanar oxygen res ...

AMER PHYSICAL SOC2020

Orbitally selective breakdown of Fermi liquid quasiparticles in Ca1.8Sr0.2RuO4

Marco Grioni, Johan Juul Chang, Gianmarco Gatti, Valeria Granata

We present a comprehensive angle-resolved photoemission spectroscopy study of Ca1.8Sr0.2RuO4. Four distinct bands are revealed and along the Ru-O bond direction their orbital characters are identified through a light polarization analysis and comparison to ...

AMER PHYSICAL SOC2019

Time-Reversal Symmetry Breaking in Re-Based Superconductors

Joël Mesot, Johan Juul Chang

To trace the origin of time-reversal symmetry breaking (TRSB) in Re-based superconductors, we performed comparative muon-spin rotation and relaxation (mu SR) studies of superconducting noncentrosymmetric Re0.82Nb0.18 (T-c = 8.8 K) and centrosymmetric Re (T ...

AMER PHYSICAL SOC2018

Magnetic-field-induced spin excitations and renormalized spin gap of the underdoped La1.895Sr0.105CuO4 superconductor

Henrik Moodysson Rønnow, Joël Mesot, Johan Juul Chang

High-resolution neutron inelastic scattering experiments in applied magnetic fields have been performed on La1.895Sr0.105CuO4 (LSCO). In zero field, the temperature dependence of the low-energy peak intensity at the incommensurate momentum transfer Q(IC)=( ...

AMERICAN PHYSICAL SOC2007

Pseudogap suppression by competition with superconductivity in La-based cuprates

Johan Juul Chang, Claudia Giuseppina Fatuzzo

We carried out a comprehensive high-resolution angle-resolved photoemission spectroscopy (ARPES) study of the pseudogap interplay with superconductivity in La-based cuprates. The three systems La2-xSrxCuO4, La1.6-xNd0.4SrxCuO4, and La1.8-xEu0.2SrxCuO4 disp ...

AMER PHYSICAL SOC2022

Electron scattering, charge order, and pseudogap physics in La1.6-xNd0.4SrxCuO4: An angle-resolved photoemission spectroscopy study

Joël Mesot, Marco Grioni, Martin Mansson, Johan Juul Chang, Claudia Giuseppina Fatuzzo, Sara Fatale

We report an angle-resolved photoemission study of the charge stripe ordered La1.6-xNd0.4SrxCuO4 (Nd-LSCO) system. A comparative and quantitative line-shape analysis is presented as the system evolves from the overdoped regime into the charge ordered phase ...

Amer Physical Soc2015

Strain-engineering Mott-insulating La2CuO4

Henrik Moodysson Rønnow, Johan Juul Chang, Thorsten Schmitt, Noore Elahi Shaik, Yi Tseng, Yu-Pei Tseng

The transition temperature T-c of unconventional superconductivity is often tunable. For a monolayer of FeSe, for example, the sweet spot is uniquely bound to titanium-oxide substrates. By contrast for La2-xSrxCuO4 thin films, such substrates are sub-optim ...

Nature Research2019

Spectroscopic evidence for preformed Cooper pairs in the pseudogap phase of cuprates

Joël Mesot, Martin Mansson, Johan Juul Chang

Angle-resolved photoemission on underdoped La1.895Sr0.105CuO4 reveals that in the pseudogap phase, the dispersion has two branches located above and below the Fermi level with a minimum at the Fermi momentum. This is characteristic of the Bogoliubov disper ...

2009

Tuning competing orders in La2-xSrxCuO4 cuprate superconductors by the application of an external magnetic field

Henrik Moodysson Rønnow, Joël Mesot, Johan Juul Chang

We report the results of a combined muon-spin rotation and neutron-scattering study on La2-xSrxCuO4 in the vicinity of the so-called 1/8 anomaly. Application of a magnetic field drives the system toward a magnetically ordered spin-density-wave state, which ...

AMER PHYSICAL SOC2008

Hallmarks of Hunds coupling in the Mott insulator Ca2RuO4

Henrik Moodysson Rønnow, Marco Grioni, Johan Juul Chang, Simon Karl Moser, Gianmarco Gatti, Claudia Giuseppina Fatuzzo

A paradigmatic case of multi-band Mott physics including spin-orbit and Hund's coupling is realized in Ca2RuO4. Progress in understanding the nature of this Mott insulating phase has been impeded by the lack of knowledge about the low-energy electronic str ...

Nature Research2017

Electronic structure near the 1/8-anomaly in La-based cuprates

Joël Mesot, Martin Mansson, Johan Juul Chang

We report an angle-resolved photoemission study of the electronic structure of the pseudogap state in La1.48Nd0.4Sr0.12CuO4 (T-c < 7 K). Two opposite dispersing Fermi arcs are the main result of this study. Several scenarios that can explain this observati ...

Institute of Physics (IoP) and Deutsche Physikalische Gesellschaft2008

Charge-Stripe Order and Superconductivity in Ir1−xPtxTe2

Yixing Chen, László Forró, Henrik Moodysson Rønnow, Johan Juul Chang, Edoardo Martino, Andrea Pisoni, Lin Yang, Péter Krisztián Matus

A combined resistivity and hard x-ray diffraction study of superconductivity and charge ordering in Ir Ir1−xPtxTe2, as a function of Pt substitution and externally applied hydrostatic pressure, is presented. Experiments are focused on samples near the crit ...

Nature Research2017

Magnetic-Field-Induced Soft-Mode Quantum Phase Transition in the High-Temperature Superconductor La1.855Sr0.145CuO4: An Inelastic Neutron-Scattering Study

Henrik Moodysson Rønnow, Joël Mesot, Johan Juul Chang

Inelastic neutron-scattering experiments on the high-temperature superconductor La1.855Sr0.145CuO4 reveal a magnetic excitation gap Delta that decreases continuously upon application of a magnetic field perpendicular to the CuO2 planes. The gap vanishes at ...

2009

Anomalous Magnetic Excitations of Cooperative Tetrahedral Spin Clusters

Helmuth Berger, Henrik Moodysson Rønnow, Joël Mesot, Johan Juul Chang, Krunoslav Prsa

An inelastic neutron scattering study of Cu2Te2O5X2 (X=Cl, Br) shows strong dispersive modes with large energy gaps persisting far above T-N, notably in Cu2Te2O5Br2. The anomalous features: a coexisting unusually weak Goldstone-like mode observed in Cu2Te2 ...

2009