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Consortium of Swiss Academic Libraries

An introduction to the problem of bridging quantum and classical dynamics

Bonella, S. ; Ciccotti, G.

In: The European Physical Journal Special Topics, 2015, vol. 224, no. 12, p. 2305-2320

Consortium of Swiss Academic Libraries

Exponential Decay of Correlations Implies Area Law

Brandão, Fernando ; Horodecki, Michał

In: Communications in Mathematical Physics, 2015, vol. 333, no. 2, p. 761-798

Consortium of Swiss Academic Libraries

Torus Knots in Lens Spaces and Topological Strings

Stevan, Sebastien

In: Annales Henri Poincaré, 2015, vol. 16, no. 8, p. 1937-1967

Université de Fribourg

Infrared study of the multiband low-energy excitations of the topological antiferromagnet MnBi2Te4

Xu, Bing ; Zhang, Y. ; Alizade, E. H. ; Jahangirli, Z. A. ; Lyzwa, Fryderyk ; Sheveleva, Evgeniia ; Marsik, Premysl ; Li, Y. K. ; Yao, Y. G. ; Wang, Z. W. ; Shen, B. ; Dai, Y. M. ; Kataev, V. ; Otrokov, M. M. ; Chulkov, E. V. ; Mamedov, N. T. ; Bernhard, Christian

In: Physical Review B, 2021, vol. 103, no. 12, p. L121103

With infrared spectroscopy, we studied the bulk electronic properties of the topological antiferromagnet MnBi2Te4 with TN ≃ 25 K. With the support of band-structure calculations, we assign the intra- and interband excitations and determine the band gap of Eg ≈ 0.17 eV. We also obtain evidence for two types of conduction bands with light and very heavy carriers. The multiband free-carrier...

Université de Fribourg

Optical signatures of multifold fermions in the chiral topological semimetal CoSi

Xu, Bing ; Fang, Zhenyao ; Sánchez-Martínez, Miguel-Angel ; Venderbos, Jorn W. F. ; Ni, Zhuoliang ; Qiu, Tian ; Manna, Kaustuv ; Wang, Kefeng ; Paglione, Johnpierre ; Bernhard, Christian ; Felser, Claudia ; Mele, Eugene J. ; Grushin, Adolfo G. ; Rappe, Andrew M. ; Wu, Liang

In: Proceedings of the National Academy of Sciences, 2020, vol. 117, no. 44, p. 27104–27110

We report the optical conductivity in high-quality crystals of the chiral topological semimetal CoSi, which hosts exotic quasiparticles known as multifold fermions. We find that the optical response is separated into several distinct regions as a function of frequency, each dominated by different types of quasiparticles. The low-frequency intraband response is captured by a narrow Drude peak...

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

Unconventional free charge in the correlated semimetal Nd2Ir2O7

Wang, K. ; Xu, Bing ; Rischau, C. W. ; Bachar, N. ; Michon, B. ; Teyssier, J. ; Qiu, Y. ; Ohtsuki, T. ; Cheng, Bing ; Armitage, N. P. ; Nakatsuji, S. ; van der Marel, D.

In: Nature Physics, 2020, p. -

Nd2Ir2O7 is a correlated semimetal with the pyrochlore structure, in which competing spin–orbit coupling and electron–electron interactions are believed to induce a time- reversal symmetry-broken Weyl semimetal phase characterized by pairs of topologically protected Dirac points at the Fermi energy1,2,3,4. However, the emergent properties in these materials are far from clear, and exotic...

Université de Fribourg

Local Berry curvature signatures in dichroic angle-resolved photoelectron spectroscopy from two-dimensional materials

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

In: Science Advances, 2020, vol. 6, no. 9, p. eaay2730

Topologically nontrivial two-dimensional materials hold great promise for next- generation optoelectronic applications. However, measuring the Hall or spin-Hall response is often a challenge and practically limited to the ground state. An experimental technique for tracing the topological character in a differential fashion would provide useful insights. In this work, we show that circular...