A5019160326- Physics of Superconductivity and Magnetism
- Optical Network Technologies
- Quantum and electron transport phenomena
- Advanced Photonic Communication Systems
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Photonic and Optical Devices
- Advanced Fiber Laser Technologies
- Advanced Optical Network Technologies
- Magnetic properties of thin films
- Semiconductor Lasers and Optical Devices
- Cold Atom Physics and Bose-Einstein Condensates
- Theoretical and Computational Physics
- Advanced Wireless Communication Techniques
- Cellular Automata and Applications
- Advanced Chemical Physics Studies
- Photonic Crystal and Fiber Optics
- Nonlinear Waves and Solitons
- Optical Wireless Communication Technologies
- Magnetic Properties and Applications
- Error Correcting Code Techniques
- Quantum, superfluid, helium dynamics
- Electronic and Structural Properties of Oxides
- Iron-based superconductors research
- PAPR reduction in OFDM
Huawei Technologies (France)
2016-2025
Russian Quantum Center
2018
TU Wien
2018
Huawei Technologies (China)
2016
Yonsei University
2016
Institut de Physique Théorique
2014-2015
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2014-2015
Centre National de la Recherche Scientifique
2011-2015
École Polytechnique
2011-2013
Centre de Physique Théorique
2011-2013
The inclusion of strong electronic correlations into a theoretical description solids is notoriously hard problem. This review describes various recent schemes to improve on dynamical mean field theory, which includes only local correlations, by systematically incorporating nonlocal as well, and discusses applications standard models strongly correlated electrons.
We study the expansion of single-particle and two-particle imaginary-time Matsubara Green's functions quantum impurity models in basis Legendre orthogonal polynomials. discuss various applications within dynamical mean-field theory (DMFT) framework. The method provides a more compact representation than standard frequencies, therefore significantly reduces memory-storage size these quantities. Moreover, it can be used as an efficient noise filter for physical quantities continuous-time Monte...
The proximity of the Fermi surface to van Hove singularities drastically enhances interaction effects and leads essentially new physics. In this work we address formation flat bands ("Fermi condensation") within Hubbard model on triangular lattice provide a detailed analysis from an analytical numerical perspective. To describe effect consider both weak-coupling strong-coupling approaches, namely renormalization group dual fermion methods. It is shown that band flattening driven by...
We propose efficient measurement procedures for the self-energy and vertex function of Anderson impurity model within hybridization expansion continuous-time quantum Monte Carlo algorithm. The method is based on higher-order correlation functions related to quantities being sought through equation motion, a technique previously introduced in NRG context. For case interactions density-density type, additional correlators can be obtained at essentially no computational cost. In combination...
The dual boson method provides a systemic way to do diagrammatic expansion on top of extended dynamical mean-field theory (EDMFT) and can be very useful for the computational research many strongly correlated systems. authors present first application give detail description both its analytical basis numeral realization.
We present a novel approach to long-range correlations beyond dynamical mean-field theory, through ladder approximation dual fermions. The new technique is applied the two-dimensional Hubbard model. demonstrate that transformed perturbation series for nonlocal fermions has superior convergence properties over standard diagrammatic techniques. critical N\'eel temperature of solution suppressed in approximation, accordance with quantum Monte Carlo results. An illustration how captures and...
We present an approach which is based on the one-particle irreducible (1PI) generating functional formalism and includes electronic correlations all length scales beyond local of dynamical mean-field theory (DMFT). This allows us to unify aspects vertex approximation (D$\ensuremath{\Gamma}$A) dual fermion (DF) scheme, yielding a consistent formulation nonlocal at one- two-particle level DMFT within integral formalism. In particular, considered reducible contributions from three-...
We study the charge-density dynamics within two-dimensional extended Hubbard model in presence of long-range Coulomb interaction across metal-insulator transition point. To take into account strong correlations we start from self-consistent dynamical mean-field theory and include nonlocal vertex corrections through a ladder approximation to polarization operator. This is necessary fulfill charge conservation describe plasmons correlated state. The calculated plasmon spectra are qualitatively...
We consider the collective, long-wavelength charge excitations in correlated media presence of short- and long-range forces. As an example for case a short-range interaction, we examine two-dimensional Hubbard model within dynamical mean-field theory (DMFT). It is shown explicitly that DMFT susceptibility including vertex corrections respects Ward identity yields manifestly gauge-invariant response finite dimensions. For computing susceptibility, use different expression establish its formal...
We examine the nature of transition to antiferromagnetically ordered state in half-filled three-dimensional Hubbard model using dual-fermion multiscale approach. Consistent with analytics, weak-coupling regime we find that spin-flip excitations across Fermi surface are important and strong-coupling is described by Heisenberg physics. In intermediate-interaction, strong-correlation aspects both local nonlocal correlations. analyze critical exponents them be consistent physics down an...
Polarization-division multiplexed (PDM) transmission based on the nonlinear Fourier transform (NFT) is proposed for optical fiber communication. The NFT algorithms are generalized from scalar Schrödinger equation one polarization to Manakov system two polarizations. performance of PDM frequency-division multiplexing (NFDM) and orthogonal (OFDM) determined. It shown that in terms Q-factor approximately same PDM-NFDM single NFDM at twice data rate polarization-mode dispersion does not...
We propose a new four-dimensional orthant-symmetric 128-ary modulation format (4D-OS128) with spectral efficiency of 7 bit/4D-sym. The proposed fills the gap between polarization-multiplexed 8- and 16-ary quadrature-amplitude (PM-8QAM PM-16QAM). Numerical simulations show that 4D-OS128 outperforms two well-studied 4D geometrically-shaped formats: 128SP-16QAM 7b4D-2A8PSK by up to 0.65 dB for bit-interleaved coded at same efficiency. These gains are experimentally demonstrated in 11×233 Gbit/s...
In this paper, we show how the two-particle Green function can be obtained within framework of dual fermion approach. This facilitates calculation susceptibility in strongly correlated systems where long-ranged nonlocal correlations cannot neglected. We formulate Bethe--Salpeter equations for full vertex particle-particle and particle-hole channels introduce an approximation practical calculations. The scheme is applied to two-dimensional Hubbard model at half-filling. spin-spin found...
Optimized measurements for the susceptibility, self-energy, as well three-leg and four-leg vertex functions are introduced continuous-time hybridization-expansion quantum Monte Carlo solver impurity model in presence of a retarded interaction. The self-energy computed from averages which involve time integrals over They can be evaluated efficiently within segment representation. These quantities dynamical mean-field theory plasmonic screening. In antiadiabatic regime, is strongly...
In the study of strongly interacting systems, correlations on two-particle level are receiving more and attention. this work, we a particular correlation function: fermion-boson vertex. It describes response Green's function when an external field is applied important ingredient diagrammatic extensions dynamical mean-field theory. We provide several perspectives object, using Ward identities, sum rules, perturbative analysis, asymptotic relations. then use these tools to vertex across...
In this paper, a new four-dimensional 64-ary polarization ring switching (4D-64PRS) modulation format with spectral efficiency of 6 bit/4D-sym is introduced. The designed by maximizing the generalized mutual information (GMI) and imposing constant-modulus on 4D structure. proposed yields an improved performance respect to state-of-the-art geometrically shaped formats for bit-interleaved coded systems at same efficiency. Unlike previously published results, coordinates constellation points...
Recent advances in multi-band amplification support ultra-wideband (UWB) systems as a suitable solution to cope with the increasing fiber communications traffic demand. The combination of UWB spectral-efficient modulation formats can significantly increase total throughput wavelength division multiplexed (WDM) transmission systems. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In this work, we demonstrate 240×70 Gbaud PCS-256QAM WDM using an...
We present a very efficient solver for the general Anderson impurity problem. It is based on perturbation around solution obtained from exact diagonalization, using small number of bath sites. formulate theory which valid both weak and strong coupling interpolates between these limits. Good agreement with numerically quantum Monte Carlo results found single site over wide range parameters. In particular, Kondo resonance in intermediate-coupling regime well reproduced lowest-order correction....
Abstract The integrable nonlinear Schrödinger equation (NLSE) is a fundamental model of science which also has important consequences in engineering. powerful framework the periodic inverse scattering transform (IST) provides description phenomena modulational instability and Fermi-Pasta-Ulam-Tsingou (FPUT) recurrence terms exact solutions. It associates complex dynamics with invariant spectral degrees freedom that may be used to encode information. While optical fiber an ideal testing...
In this paper, we study the connection between polar codes and product codes. Our analysis shows that of two is again a code, provide guidelines to compute its frozen set on basis sets component Moreover, show how can be described as irregular We propose two-step decoder for long taking advantage dual nature heavily reduce decoding latency. Finally, proposed technique outperforms both standard state-of-the-art optical communications under latency constraints.
Digital twins capable of quality transmission (QoT) estimation and prediction are powerful tools for efficient design operation optical networks. In this paper, we employ machine learning techniques to enhance both the QoT capabilities an network digital twin. By leveraging a method infer or refine unknown lumped loss distributions amplifier gain spectra accurate characterization current state, accuracy is substantially improved. For prediction, further develop novel neural-network...