Affiner les résultats

Langue

Université de Fribourg

Total Angular Momentum Dichroism of the Terahertz Vortex Beams at the Antiferromagnetic Resonances

Sirenko, Andrei A. ; Marsik, Premysl ; Bugnon, Laurent ; Soulier, Mathias ; Bernhard, Christian ; Stanislavchuk, T. N. ; Xu, Xianghan ; Cheong, S.-W.

In: Physical Review Letters, 2021, vol. 126, no. 15, p. 157401

Terahertz vortex beams with different superposition of the orbital angular momentum $l={\pm}1$, ${\pm}2$, ${\pm}3$, and ${\pm}4$ and spin angular momentum ${\sigma}={\pm}1$ were used to study antiferromagnetic (AFM) resonances in TbFe$_3$(BO$_3$)$_4$ and Ni$_3$TeO$_6$ single crystals. In both materials we observed a strong vortex beam dichroism for the AFM resonances that are split in ...

Université de Fribourg

How circular dichroism in time- and angle-resolved photoemission can be used to spectroscopically detect transient topological states in graphene

Schüler, Michael ; Giovannini, Umberto De ; Hübener, Hannes ; Rubio, Angel ; Sentef, Michael A. ; Devereaux, Thomas P. ; Werner, Philipp

In: Physical Review X, 2020, vol. 10, no. 4, p. 041013

Pumping graphene with circularly polarized light is the archetype of light-tailoring topological bands. Realizing the induced Floquet-Chern-insulator state and demonstrating clear experimental evidence for its topological nature has been a challenge, and it has become clear that scattering effects play a crucial role. We tackle this gap between theory and experiment by employing microscopic...

Université de Fribourg

High-harmonic generation in spin-orbit coupled systems

Lysne, Markus ; Murakami, Yuta ; Schüler, Michael ; Werner, Philipp

In: Physical Review B, 2020, vol. 102, no. 8, p. 081121

We study high-harmonic generation in two-dimensional electron systems with Rashba and Dresselhaus spin-orbit coupling and derive harmonic generation selection rules with the help of group theory. Based on the band structures of these minimal models and explicit simulations we reveal how the spin-orbit parameters control the cutoff energy in the high-harmonic spectrum. We also show that the...

Université de Fribourg

Hund excitations and the efficiency of Mott solar cells

Petocchi, Francesco ; Beck, Sophie ; Ederer, Claude ; Werner, Philipp

In: Physical Review B, 2019, vol. 100, no. 7, p. 075147

We study the dynamics of photoinduced charge carriers in semirealistic models of LaVO3 and YTiO3 polar heterostructures. It is shown that two types of impact ionization processes contribute to the carrier multiplication in these strongly correlated multiorbital systems: The first mechanism involves local spin state transitions, while the second mechanism involves the scattering of...

Université de Fribourg

Magnetic-field effects on one-dimensional Anderson localization of light

Schertel, Lukas ; Irtenkauf, Oliver ; Aegerter, Christof M. ; Maret, Georg ; Aubry, Geoffroy J.

In: Physical Review A, 2019, vol. 100, no. 4, p. 043818

Transport of coherent waves in multiple-scattering media may exhibit fundamental, nonintuitive phenomena such as halt of diffusion by disorder called Anderson localization. For electromagnetic waves, this phenomenon was observed only in one and two dimensions so far. However, none of these experiments studied the contribution of reciprocal paths nor their manipulation by external fields. In...

Université de Fribourg

Terahertz vortex beam as a spectroscopic probe of magnetic excitations

Sirenko, Andrei A. ; Maršík, Premysl ; Bernhard, Christian ; Stanislavchuk, T. N. ; Kiryukhin, V. ; Cheong, S.-W.

In: Physical Review Letters, 2019, vol. 122, no. 23, p. 237401

Circularly polarized light with spin angular momentum is one of the most valuable probes of magnetism. We demonstrate that light beams with orbital angular momentum (OAM), or vortex beams, can also couple to magnetism exhibiting dichroisms in a magnetized medium. Resonant optical absorption in a ferrimagnetic crystal depends strongly on both the handedness of the vortex and the direction of...

Université de Fribourg

Continuous magnetic phase transition in artificial square ice

Sendetskyi, Oles ; Scagnoli, Valerio ; Leo, Naëmi ; Anghinolfi, Luca ; Alberca, Aurora ; Lüning, Jan ; Staub, Urs ; Derlet, Peter Michael ; Heyderman, Laura Jane

In: Physical Review B, 2019, vol. 99, no. 21, p. 214430

Critical behavior is very common in many fields of science and a wide variety of many- body systems exhibit emergent critical phenomena. The beauty of critical phase transitions lies in their scale-free properties, such that the temperature dependence of physical parameters of systems differing at the microscopic scale can be described by the same generic power laws. In this work we establish...

Université de Fribourg

Phase transformation of superparamagnetic iron oxide nanoparticles via thermal annealing: implications for hyperthermia applications

Crippa, Federica ; Rodriguez-Lorenzo, Laura ; Hua, Xiao ; Goris, Bart ; Bals, Sara ; Garitaonandia, José S. ; Balog, Sandor ; Burnand, David ; Hirt, Ann M. ; Haeni, Laetitia ; Lattuada, Marco ; Rothen-Rutishauser, Barbara ; Petri-Fink, Alke

In: ACS Applied Nano Materials, 2019, vol. 2, no. 7, p. 4462–4470

Magnetic hyperthermia has the potential to play an important role in cancer therapy and its efficacy relies on the nanomaterials selected. Superparamagnetic iron oxide nanoparticles (SPIONs) are excellent candidates due to the ability of producing enough heat to kill tumor cells by thermal ablation. However, their heating properties depend strongly on crystalline structure and size, which may...