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Electronic Structure and Properties of Superconducting Materials with Simple Fermi Surfaces

Jarlborg, T.

In: Journal of Superconductivity and Novel Magnetism, 2015, vol. 28, no. 4, p. 1231-1236

Université de Fribourg

Muon spin rotation and infrared spectroscopy study of Ba$_{1-x}$Na$_{x}$Fe$_{2}$As$_{2}$

Sheveleva, Evgeniia ; Xu, Bing ; Marsik, Premysl ; Lyzwa, Fryderyk ; Mallett, Benjamin P. P. ; Willa, K. ; Meingast, C. ; Wolf, Th. ; Shevtsova, T. ; Pashkevich, Yu. G. ; Bernhard, Christian

In: Physical Review B, 2020, vol. 101, no. 22, p. 224515

The magnetic and superconducting properties of a series of underdoped Ba 1 − x Na x Fe 2 As 2 (BNFA) single crystals with 0.19 ≤ x ≤ 0.34 have been investigated with the complementary muon-spin-rotation ( μ SR ) and infrared spectroscopy techniques. The focus has been on the different antiferromagnetic states in the underdoped regime and their competition with superconductivity,...

Université de Fribourg

Superconducting and antiferromagnetic properties of dual-phase V3Ga

Jamer, Michelle E. ; Wilfong, Brandon ; Buchelnikov, Vasiliy D. ; Sokolovskiy, Vladimir V. ; Miroshkina, Olga N. ; Zagrebin, Mikhail A. ; Baigutlin, Danil R. ; Naphy, Jared ; Assaf, Badih A. ; Lewis, Laura H. ; Pulkkinen, Aki ; Barbiellini, Bernardo ; Bansil, Arun ; Heiman, Don

In: Applied Physics Letters, 2020, vol. 117, no. 6, p. 062401

The binary compound V3Ga can exhibit two near-equilibrium phases, the A15 structure that is superconducting and the Heusler D03 structure that is semiconducting and antiferromagnetic. Density functional theory calculations show that these two phases are nearly degenerate, being separated in energy by only ±10 meV/atom. Our magnetization measurements on bulk-grown samples show ...

Université de Fribourg

Superconductivity-induced transverse plasma mode and phonon anomaly in the $c$-axis response of the bilayer compound ${\mathrm{RbCa}}_{2}{\mathrm{Fe}}_{4}{\mathrm{As}}_{4}{\mathrm{F}}_{2}$

Xu, Bing ; Munzar, Dominik ; Dubroka, Adam ; Sheveleva, Evgeniia ; Lyzwa, Fryderyk ; Maršík, Premysl ; Wang, C. N. ; Wang, Z. C. ; Cao, G. H. ; Bernhard, Christian

In: Physical Review B, 2020, vol. 101, no. 21, p. 214512

We studied the infrared response of polycrystalline samples of the iron arsenide superconductor (Rb,Cs)Ca2Fe4As4F2 (Rb,Cs-12442), which has a bilayer structure similar to the high-Tc cuprates YBa2Cu3O7 (YBCO) and Bi2Sr2CaCu2O8. The c-axis reflectivity spectra Rc have been derived from the reflectivity spectra of the polycrystalline samples Rpoly and the in-plane spectrum of a corresponding...

Université de Fribourg

Infrared spectroscopy study of the in-plane response of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.6}$ in magnetic fields up to 30 Tesla

Lyzwa, Fryderyk ; Xu, Bing ; Maršík, Premysl ; Sheveleva, Evgeniia ; Crassee, I. ; Orlita, M. ; Bernhard, Christian

In: Physical Review Research, 2020, vol. 2, no. 2, p. 023218

With terahertz and infrared spectroscopy we studied the in-plane response of an underdoped, twinned YBa2Cu3O6.6 single crystal with Tc=58(1)K in high magnetic fields up to B=30 Tesla (T) applied along the c axis. Our goal was to investigate the field-induced suppression of superconductivity and to observe the signatures of the three-dimensional (3D) incommensurate copper charge density wave...

Université de Fribourg

Magneto-transport in La2/3Sr1/3MnO3/YBa2Cu3O7/Alq3/Co spin-valves

Cerreta, Andrea ; Gaina, Roxana ; Nuccio, Laura ; Marozau, Ivan ; Sen, Kaushik ; De Andrés Prada, Roberto ; Sarkar, Subhrangsu ; Bernhard, Christian

In: EPL (Europhysics Letters), 2020, vol. 129, no. 3, p. 37002

We studied how an additional layer of the high superconductor YBCO affects the magneto-transport across a LSMO/Alq3/Co spin-valve structure. We found that up to a thickness of at least 10 nm the YBCO layer on top of LSMO hardly changes the spin-valve effect, since the device resistance still depends on the relative orientation of the LSMO and Co magnetization. The spin-valve effect persists...

Université de Fribourg

Nickelate superconductors: multiorbital nature and spin freezing

Werner, Philipp ; Hoshino, Shintaro

In: Physical Review B, 2020, vol. 101, no. 4, p. 041104

Superconductivity with a remarkably high Tc has recently been found in Sr-doped NdNiO2 thin films. While this system bears strong similarities to the cuprates, some differences, such as a weaker antiferromagnetic exchange coupling and possible high-spin moments on the doped Ni sites have been pointed out. Here, we investigate the effect of Hund coupling and crystal field splitting in a simple...

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

Granular superconductivity and charge/orbital order in YBa 2 Cu 3 O 7 /manganite trilayers

Khmaladze, Jarji ; Sarkar, Subhrangsu ; Soulier, Mathias ; Lyzwa, Fryderyk ; Prada, R. de Andres ; Perret, Edith ; Mallett, Benjamin P. P. ; Minola, M. ; Keimer, B. ; Bernhard, Christian

In: Physical Review Materials, 2019, vol. 3, no. 8, p. 084801

We studied how the electronic, superconducting, and magnetic properties of YBa2Cu3O7/Nd1−x(Ca1−ySry )xMnO3 multilayers depend on the tolerance factor and the hole doping of the manganite. In particular, we investigated the granular superconducting state and the related magnetic-field-driven insulator-to- superconductor transition that was previously discovered in corresponding multilayers...