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Université de Neuchâtel

Semiconductor disk laser-based frequency combs

Jornod, Nayara ; Südmeyer, Thomas (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2018.

Cette thèse présente une étude des premiers peignes de fréquences auto-référencés basés sur des lasers à disques semi-conducteurs (SDLs) à modes verrouillés en phase. L’avènement des peignes de fréquences stabilisés basés sur des lasers à impulsions ultra-courtes a permis une avancée significative et de nombreuses applications dans divers domaines de la physique, de la...

Université de Neuchâtel

Measurement of the linewidth enhancement factor of singlemode room temperature continuous wave quantum cascade lasers

Aellen, Thierry ; Aebi, Philipp (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2008.

L'invention des sources lasers en 1960 a conduit à un bon nombre d'applications qui ont un impact répandu dans tous les aspects de notre votre vie actuelle, citons notamment l'exemple des hôpitaux, de l'industrie ou simplement dans notre lieu de vie. Les derniers développements sont en particulier issus des compacts, très efficace et populaires lasers semiconducteurs qui sont simplement...

Université de Fribourg

Social signature identification of dynamical social networks

Li, Ren-De ; Liu, Jian-Guo ; Guo, Qiang ; Zhang, Yi-Cheng

In: Physica A: Statistical Mechanics and its Applications, 2018, vol. 508, p. 213–222

Understanding the social relation of dynamical online social networks (OSNs) is significant for identifying the strong and weak ties. In this paper, we empirically investigate the evolution characteristics of Facebook and Wiki users’ social signature, capturing the distribution of frequency of interactions between different alters over time in ego network. The statistical results show that...

Université de Fribourg

Structure-oriented prediction in complex networks

Ren, Zhuo-Ming ; Zeng, An ; Zhang, Yi-Cheng

In: Physics Reports, 2018, vol. 750, p. 1–51

Complex systems are extremely hard to predict due to its highly nonlinear interactions and rich emergent properties. Thanks to the rapid development of network science, our understanding of the structure of real complex systems and the dynamics on them has been remarkably deepened, which meanwhile largely stimulates the growth of effective prediction approaches on these systems. In this...

Université de Fribourg

Enhancing countries’ fitness with recommender systems on the international trade network

Liao, Hao ; Huang, Xiao-Min ; Wu, Xing-Tong ; Liu, Ming-Kai ; Vidmer, Alexandre ; Zhou, Ming-Yang ; Zhang, Yi-Cheng

In: Complexity, 2018, p. -

Prediction is one of the major challenges in complex systems. The prediction methods have shown to be effective predictors of the evolution of networks. These methods can help policy makers to solve practical problems successfully and make better strategy for the future. In this work, we focus on exporting countries’ data of the International Trade Network. A recommendation system is then...

Université de Fribourg

Quantum Boltzmann equation for strongly correlated systems: Comparison to dynamical mean field theory

Wais, Michael ; Eckstein, Martin ; Fischer, R. ; Werner, Philipp ; Battiato, M. ; Held, K.

In: Physical Review B, 2018, vol. 98, no. 13, p. 134312

We investigate the potential of a quantum Boltzmann equation without momentum conservation for description of strongly correlated electron systems out of equilibrium. In a spirit similar to dynamical mean field theory (DMFT), the momentum conservation of the electron-electron scattering is neglected, which yields a time-dependent occupation function for the equilibrium spectral function, even...

Université de Fribourg

Nonequilibrium steady states of electric field driven Mott insulators

Murakami, Yuta ; Werner, Philipp

In: Physical Review B, 2018, vol. 98, no. 7, p. 075102

We present a systematic study of the nonequilibrium steady states (NESS) in Mott insulators driven by dc or ac electric fields, based on the Floquet dynamical mean- field theory. The results are analyzed using a generalized tunneling formula for the current, which is reminiscent of the Meir-Wingreen formula and provides insights into the relevant physical processes. In the dc case, the...

Université de Fribourg

Linear behavior of the optical conductivity and incoherent charge transport in ${\mathrm{BaCoS}}_{2}$

Santos-Cottin, D. ; Klein, Y. ; Werner, Philipp ; Miyake, Takashi ; Medici, L. de ; Gauzzi, A. ; Lobo, R. P. S. M. ; Casula, Michele

In: Physical Review Materials, 2018, vol. 2, no. 10, p. 105001

Optical conductivity measurements on a BaCoS2 single crystal unveil an unusual linear behavior over a broad spectral range. In the paramagnetic phase above 300 K, the spectrum shows no gap, which contradicts the previously proposed scenario of a charge-transfer Mott insulator. Ab initio dynamical mean field theory calculations including a retarded Hubbard interaction explain the data in terms...

Université de Fribourg

High-harmonic generation in Mott insulators

Murakami, Yuta ; Eckstein, Martin ; Werner, Philipp

In: Physical Review Letters, 2018, vol. 121, no. 5, p. 057405

Using Floquet dynamical mean-field theory, we study the high-harmonic generation in the time-periodic steady states of wide-gap Mott insulators under ac driving. In the strong-field regime, the harmonic intensity exhibits multiple plateaus, whose cutoff energies εcut=U+mE0 scale with the Coulomb interaction U and the maximum field strength E0. In this regime, the created doublons and holons...

Université de Fribourg

Instability in stable marriage problem: matching unequally numbered men and women

Shi, Gui-Yuan ; Kong, Yi-Xiu ; Chen, Bo-Lun ; Yuan, Guang-Hui ; Wu, Rui-Jie

In: Complexity, 2018, p. -

The goal of the stable marriage problem is to match by pair two sets composed by the same number of elements. Due to its widespread applications in the real world, especially the unique importance to the centralized matchmaker, a very large number of questions have been extensively studied in this field. This article considers a generalized form of the stable marriage problem, where different...