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Université de Fribourg

Resonance raman optical activity shows unusual structural sensitivity for systems in resonance with multiple excited states: vitamin B12 case

Machalska, Ewa ; Zajac, Grzegorz ; Gruca, Anna ; Zobi, Fabio ; Baranska, Malgorzata ; Kaczor, Agnieszka

In: The Journal of Physical Chemistry Letters, 2020, vol. 11, no. 13, p. 5037–5043

In this work, cobalamins with different upper axial substituents and a cobalamin derivative with a ring modification were studied using chiroptical spectroscopies, in particular resonance Raman optical activity (RROA), to shed light on the influence of structural modifications on RROA spectra in these strongly chiral systems in resonance with multiple excited states at 532 nm excitation. We...

Université de Fribourg

Analysis method for detecting topological defect dark matter with a global magnetometer network

Masia-Roig, Hector ; A.Smiga, Joseph ; Budker, Dmitry ; Dumont, Vincent ; Gruji, Zoran ; Kim, Dongok ; Kimball, Derek F. Jackson ; Lebedev, Victor ; Monroy, Madeline ; Pustelny, Szymon ; Scholtes, Theo ; Segura, Perrin C. ; Semertzidi, Yannis K. ; Shin, Yun Chang ; Stalnaker, Jason E. ; Sulai, Ibrahim ; Weis, Antoine ; Wickenbrock, Arne

In: Physics of the Dark Universe, 2020, vol. 28, p. 100494

The Global Network of Optical Magnetometers for Exotic physics searches (GNOME) is a network of time-synchronized, geographically separated, optically pumped atomic magnetometers that is being used to search for correlated transient signals heralding exotic physics. GNOME is sensitive to exotic couplings of atomic spins to certain classes of dark matter candidates, such as axions. This work...

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

Resolution limit of taylor dispersion: an exact theoretical study

Taladriz-Blanco, Patricia ; Rothen-Rutishauser, Barbara ; Petri-Fink, Alke ; Balog, Sandor

In: Analytical Chemistry, 2020, vol. 92, no. 1, p. 561–566

Taylor dispersion is a microfluidic analytical technique with a high dynamic range and therefore is suited well to measuring the hydrodynamic radius of small molecules, proteins, supramolecular complexes, macromolecules, nanoparticles and their self- assembly. Here we calculate an unaddressed yet fundamental property: the limit of resolution, which is defined as the smallest change in the...

Université de Fribourg

Electronic structure and photoluminescence properties of Eu(η9-C9H9)2

Ramanantoanina, Harry ; Merzoud, Lynda ; Muya, Jules Tshishimbi ; Chermette, Henry ; Daul, Claude

In: The Journal of Physical Chemistry A, 2020, vol. 124, no. 1, p. 152–164

The electronic structure of Eu2+ compounds results from a complex combination of strongly correlated electrons and relativistic effects as well as weak ligand–field interaction. There is tremendous interest in calculating the electronic structure as nowadays the Eu2+ ion is becoming more and more crucial, for instance, in lighting technologies. Recently, interest in semiempirical methods to...

Université de Fribourg

Classification and characterization of nonequilibrium Higgs modes in unconventional superconductors

Schwarz, L. ; Fauseweh, B. ; Tsuji, N. ; Cheng, N. ; Bittner, Nikolaj ; Krull, H. ; Berciu, M. ; Uhrig, G.S. ; Schnyder, A.P. ; Kaiser, S. ; Manske, D.

In: Nature Communications, 2020, vol. 11, no. 1, p. 1–9

Recent findings of new Higgs modes in unconventional superconductors require a classification and characterization of the modes allowed by nontrivial gap symmetry. Here we develop a theory for a tailored nonequilibrium quantum quench to excite all possible oscillation symmetries of a superconducting condensate. We show that both a finite momentum transfer and quench symmetry allow for an...

Université de Neuchâtel

Towards compact ultralow phase noise lasers and microwave signals based on new approaches

Brochard, Pierre ; Südmeyer, Thomas (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2019.

Today, the lowest phase noise microwave signals are generated optically by frequency division of an ultra-stable optical reference using a femtosecond frequency comb. In the commonly used approach, the ultra-stable optical reference is obtained by frequency-stabilizing a laser to a high-finesse ultra-low expansion optical cavity, and the frequency division is performed by optically locking a...

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 Neuchâtel

Long-Term Stability Analysis Towards <10-14 Level for a Highly Compact POP Rb Cell Atomic Clock

Almat, Nil ; Gharavipour, Mohammadreza ; Moreno, William ; Gruet, Florian ; Affolderbach, Christoph ; Mileti, Gaetano

In: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2020, vol. 67, no. 1, p. 207-216

Long-term frequency instabilities in vapor-cell clocks mainly arise from fluctuations of the experimental and environmental parameters that are converted to clock frequency fluctuations via various physical processes. Here, we discuss the frequency sensitivities and the resulting stability limitations at one-day timescale for a rubidium vapor-cell clock based on a compact magnetron-type cavity...