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Consortium of Swiss Academic Libraries

Hamiltonian Anomalies from Extended Field Theories

Monnier, Samuel

In: Communications in Mathematical Physics, 2015, vol. 338, no. 3, p. 1327-1361

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

Ultrafast coupled charge and spin dynamics in strongly correlated NiO

Gillmeister, Konrad ; Golež, Denis ; Chiang, Cheng-Tien ; Bittner, Nikolaj ; Pavlyukh, Yaroslav ; Berakdar, Jamal ; Werner, Philipp ; Widdra, Wolf

In: Nature Communications, 2020, vol. 11, no. 1, p. 4095

Charge excitations across an electronic band gap play an important role in opto- electronics and light harvesting. In contrast to conventional semiconductors, studies of above-band-gap photoexcitations in strongly correlated materials are still in their infancy. Here we reveal the ultrafast dynamics controlled by Hund’s physics in strongly correlated photoexcited NiO. By combining...

Université de Fribourg

Optical and theoretical study of strand recognition by nucleic acid probes

Domljanovic, Ivana ; Taskova, Maria ; Miranda, Pâmella ; Weber, Gerald ; Astakhova, Kira

In: Communications Chemistry, 2020, vol. 3, no. 1, p. 111

Detection of nucleic acids is crucial to the study of their basic properties and consequently to applying this knowledge to the determination of pathologies such as cancer. In this work, our goal is to determine new trends for creating diagnostic tools for cancer driver mutations. Herein, we study a library of natural and modified oligonucleotide duplexes by a combination of optical and...

Université de Fribourg

Signatures of bosonic excitations in high-harmonic spectra of Mott insulators

Lysne, Markus ; Murakami, Yuta ; Werner, Philipp

In: Physical Review B, 2020, vol. 101, no. 19, p. 195139

The high-harmonic spectrum of the Mott insulating Hubbard model has recently been shown to exhibit plateau structures with cutoff energies determined by nth-nearest- neighbor doublon-holon recombination processes. The spectrum thus allows one to extract the on-site repulsion U. Here, we consider generalizations of the single-band Hubbard model and discuss the signatures of bosonic excitations...

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...

Université de Fribourg

Light-induced evaporative cooling of holes in the Hubbard model

Werner, Philipp ; Eckstein, Martin ; Müller, Markus ; Refael, Gil

In: Nature Communications, 2019, vol. 10, no. 1, p. 5556

An elusive goal in the field of driven quantum matter is the induction of long-range order. Here, we propose a mechanism based on light-induced evaporative cooling of holes in a correlated fermionic system. Since the entropy of a filled narrow band grows rapidly with hole doping, the isentropic transfer of holes from a doped Mott insulator to such a band results in a drop of temperature....

Université de Fribourg

Quantum simulation meets nonequilibrium dynamical mean-field theory: exploring the periodically driven, strongly correlated fermi-hubbard model

Sandholzer, Kilian ; Murakami, Yuta ; Görg, Frederik ; Minguzzi, Joaquín ; Messer, Michael ; Desbuquois, Rémi ; Eckstein, Martin ; Werner, Philipp ; Esslinger, Tilman

In: Physical Review Letters, 2019, vol. 123, no. 19, p. 193602

We perform an ab initio comparison between nonequilibrium dynamical mean-field theory and optical lattice experiments by studying the time evolution of double occupations in the periodically driven Fermi-Hubbard model. For off-resonant driving, the range of validity of a description in terms of an effective static Hamiltonian is determined and its breakdown due to energy absorption close to...