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Université de Fribourg

Element-specific magnetization redistribution at ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}/{\mathrm{La}}_{2/3}{\mathrm{Ca}}_{1/3}{\mathrm{MnO}}_{3}$ interfaces

Alberca, Aurora ; Uribe-Laverde, Miguel Angel ; Windsor, Y. W. ; Ramakrishnan, M. ; Rettig, L. ; Marozau, Ivan ; Tonnerre, J-M. ; Stahn, J. ; Staub, U. ; Bernhard, Christian

In: Physical Review B, 2015, vol. 92, no. 17, p. 174415

We study the element-specific magnetic depth profiles of a YBa2Cu3O7/La2/3Ca1/3MnO3 (YBCO/LCMO) superlattice using soft x-ray resonant magnetic reflectometry (XRMR). This allows us to study the magnetic proximity effect (MPE) that is observed at the YBCO/LCMO interface, characterized by the occurrence of a depleted layer on the manganite side and an induced magnetization in the YBCO. Using the...

Université de Fribourg

Memory-functionality superconductor/ferromagnet/superconductor junctions based on the high- T c cuprate superconductors YBa 2 Cu 3 O 7 − x and the colossal magnetoresistive manganite ferromagnets La 2 / 3 X 1 / 3 MnO 3 + δ ( X = Ca , Sr )

Andrés Prada, R. de ; Golod, T. ; Kapran, O. M. ; Borodianskyi, E. A. ; Bernhard, Christian ; Krasnov, V. M.

In: Physical Review B, 2019, vol. 99, no. 21, p. 214510

Complex oxides exhibit a variety of unusual physical properties, which can be used for designing novel electronic devices. Here we fabricate and study experimentally nanoscale superconductor/ferromagnet/superconductor junctions with the high-Tc cuprate superconductors YBa2Cu3O7−x and the colossal magnetoresistive (CMR) manganite ferromagnets La2/3X1/3MnO3+δ (X=Ca or Sr). We demonstrate...

Université de Fribourg

Growth and nanofabrication of all-perovskite superconducting/ferromagnetic/superconducting junctions

Andrés Prada, Roberto de ; Golod, T. ; Bernhard, Christian ; Krasnov, V. M.

In: Journal of Superconductivity and Novel Magnetism, 2019, vol. 32, no. 9, p. 2721–2726

We fabricate and study experimentally all-perovskite-oxide superconductor/ferromagnetic insulator/superconductor (S/FI/S) tunnel junctions made out of the high-temperature cuprate superconductor YBa2Cu3O7−y (YBCO) and the colossal magnetoresistive manganite LaMnO3 (LMO) in the ferromagnetic insulator state. YBCO/LMO/YBCO heterostructures with different LMO thicknesses (5, 10, and 20 nm)...

Université de Fribourg

Controlling the strength of ferromagnetic order in YBa2Cu3O7/La2/3Ca1/3MnO3 multilayers

Andrés Prada, Roberto de ; Gaina, Roxana ; Biškup, N. ; Varela, M. ; Stahn, J. ; Bernhard, Christian

In: Physical Review B, 2019, vol. 100, no. 11, p. 115129

With dc magnetization and polarized neutron reflectometry we studied the ferromagnetic response of YBa2Cu3O7/La2/3Ca1/3MnO3 (YBCO/LCMO) multilayers that are grown with pulsed laser deposition. We found that whereas for certain growth conditions (denoted as A type) the ferromagnetic moment of the LCMO layer is strongly dependent on the structural details of the YBCO layer on which it is ...

Université de Fribourg

Anomalous anisotropic exciton temperature dependence in rutile ${\mathrm{TiO}}_{2}$

Baldini, Edoardo ; Dominguez, Adriel ; Chiodo, Letizia ; Sheveleva, Evgeniia ; Yazdi-Rizi, Meghdad ; Bernhard, Christian ; Rubio, Angel ; Chergui, and Majed

In: Physical Review B, 2017, vol. 96, no. 4, p. 041204

Elucidating the details of electron-phonon coupling in semiconductors and insulators is a topic of pivotal interest, as it governs the transport mechanisms and is responsible for various phenomena such as spectral-weight transfers to phonon sidebands and self-trapping. Here, we investigate the influence of the electron-phonon interaction on the excitonic peaks of rutile TiO2, revealing a strong...

Université de Fribourg

Electron–phonon-driven three-dimensional metallicity in an insulating cuprate

Baldini, Edoardo ; Sentef, Michael A. ; Acharya, Swagata ; Brumme, Thomas ; Sheveleva, Evgeniia ; Lyzwa, Fryderyk ; Pomjakushina, Ekaterina ; Bernhard, Christian ; van Schilfgaarde, Mark ; Carbone, Fabrizio ; Rubio, Angel ; Weber, Cédric

In: Proceedings of the National Academy of Sciences, 2020, vol. 117, no. 12, p. 6409-6416

The role of the crystal lattice for the electronic properties of cuprates and other high-temperature superconductors remains controversial despite decades of theoretical and experimental efforts. While the paradigm of strong electronic correlations suggests a purely electronic mechanism behind the insulator-to-metal transition, recently the mutual enhancement of the electron–electron and the...

Université de Fribourg

Lattice-mediated magnetic order melting in ${\mathrm{TbMnO}}_{3}$

Baldini, Edoardo ; Kubacka, Teresa ; Mallett, Benjamin P. P. ; Ma, Chao ; Koohpayeh, Seyed M. ; Zhu, Yimei ; Bernhard, Christian ; Johnson, Steven L. ; Carbone, Fabrizio

In: Physical Review B, 2018, vol. 97, no. 12, p. 125149

Recent ultrafast magnetic-sensitive measurements [Johnson et al., Phys. Rev. B 92, 184429 (2015); Bothschafter et al., Phys. Rev. B 96, 184414 (2017)] have revealed a delayed melting of the long-range cycloid spin order in TbMnO3 following photoexcitation across the fundamental Mott-Hubbard gap. The microscopic mechanism behind this slow transfer of energy from the photoexcited carriers to...

Université de Fribourg

Clocking the onset of bilayer coherence in a high-${T}_{c}$ cuprate

Baldini, Edoardo ; Mann, Andreas ; Mallett, Benjamin P. P. ; Arrell, Christopher ; Mourik, Frank van ; Wolf, Thomas ; Mihailovic, Dragan ; Tallon, Jeffrey L. ; Bernhard, Christian ; Lorenzana, José ; Carbone, Fabrizio

In: Physical Review B, 2017, vol. 95, no. 2, p. 024501

In cuprates, a precursor state of superconductivity is speculated to exist above the critical temperature TC. Here we show via a combination of far-infrared ellipsometry and ultrafast broadband optical spectroscopy that signatures of such a state can be obtained via three independent observables in an underdoped sample of NdBa2Cu3O6+δ. The pseudogap correlations were disentangled from the...

Université de Fribourg

Strongly bound excitons in anatase TiO₂ single crystals and nanoparticles

Baldini, Eduardo ; Chiodo, Letizia ; Dominguez, A. ; Palummo, M. ; Moser, S. ; Yazdi-Rizi, Meghdad ; Auböck, G. ; Mallett, Benjamin P. P. ; Berger, Helmuth ; Magrez, Arnaud ; Bernhard, Christian ; Grioni, M. ; Rubio, Angel ; Chergui, Majed

In: Nature Communications, 2017, vol. 8, no. 1, p. 13

Anatase TiO₂ is among the most studied materials for light-energy conversion applications, but the nature of its fundamental charge excitations is still unknown. Yet it is crucial to establish whether light absorption creates uncorrelated electron–hole pairs or bound excitons and, in the latter case, to determine their character. Here, by combining steady-state angle-resolved...

Université de Fribourg

Muon spin rotation study of magnetism and superconductivity in BaFe2−xCoxAs₂ and Pr1−xSrxFeAsO

Bernhard, Christian ; Drew, Alan J. ; Schulz, Leander ; Malik, Vivek Kumar ; Rössle, Matthias ; Niedermayer, Ch. ; Wolf, Th. ; Varma, G. D. ; Mu, G. ; Wen, H.-H. ; Liu, H. ; Wu, G. ; Chen, X. H.

In: New Journal of Physics, 2009, vol. 11, p. 055050

We present a muon spin rotation (μSR) study of the magnetic and superconducting properties of single crystals of electron-doped BaFe2−xCoxAs₂ with x = 0.08, 0.20 and 0.25 (Tc = 9, 25 and 20 K) and of polycrystalline hole-doped Pr1−xSrxFeAsO with x = 0 and 0.2 (Tc = 15...