Publications by Johan Juul Chang

Search for relativistic fractionally charged particles in space

Songmei Wu, Johan Juul Chang, Zhirui Xu, Jennifer Maria Frieden, Siyuan Wang, Junqiu Liu, Jian Wang, Yi Zhang, Yong Yang, Hao Liu, Ming Gao, Cheng Zhao, Xuan Li, Arshia Ruina, Chiara Perrina, Andrii Kotenko, Wenyu Zhang, Xiao Wang, Yi Wang, Wei Li, Jie Chen, Shuai Liu, Yao Zhang

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

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

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

László Forró, Qian Wang, 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, Claudia Giuseppina Fatuzzo, Yi Tseng, Thorsten Schmitt

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

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

Strain-engineering Mott-insulating La2CuO4

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

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

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

Direct observation of orbital hybridisation in a cuprate superconductor

Martin Mansson, Johan Juul Chang, Claudia Giuseppina Fatuzzo, Thorsten Schmitt

Nature Publishing Group2018

Dispersive magnetic and electronic excitations in iridate perovskites probed by oxygen K-edge resonant inelastic x-ray scattering

Henrik Moodysson Rønnow, Johan Juul Chang, Sara Fatale, Thorsten Schmitt

2018

Nodeless superconductivity in the cage-type superconductor Sc5Ru6Sn18 with preserved time-reversal symmetry

Johan Juul Chang

2018

Spin-Orbital Excitations in Ca2RuO4 Revealed by Resonant Inelastic X-Ray Scattering

Henrik Moodysson Rønnow, Johan Juul Chang, Claudia Giuseppina Fatuzzo, Yi Tseng, Thorsten Schmitt

American Physical Society2018

Charge-Stripe Order and Superconductivity in Ir1−xPtxTe2

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

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

Hallmarks of Hunds coupling in the Mott insulator Ca2RuO4

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

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

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

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

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

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

Joël Mesot, Elia Razzoli, 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

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

Bulk Electronic Structure of Superconducting LaRu2P2 Single Crystals Measured by Soft-X-Ray Angle-Resolved Photoemission Spectroscopy

Joël Mesot, Elia Razzoli, Johan Juul Chang, Janusz Andrzej Karpinski, Thorsten Schmitt

We present a soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) study of the stoichiometric pnictide superconductor LaRu2P2. The observed electronic structure is in good agreement with density functional theory (DFT) calculations. However, it ...

2012

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

Joël Mesot, Elia Razzoli, Martin Mansson, Johan Juul Chang

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

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

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

Joël Mesot, Elia Razzoli, 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