Michael Bonitz - Academia.edu (original) (raw)
Papers by Michael Bonitz
Bulletin of the American …, 2006
... Rev. E 71, 046403 (2005) [4] M. Bonitz, D. Block, O. Arp, V. Golubnychiy, H. Baumgartner, P. ... more ... Rev. E 71, 046403 (2005) [4] M. Bonitz, D. Block, O. Arp, V. Golubnychiy, H. Baumgartner, P. Ludwig, A. Piel, and A. Filinov, Phys. Rev. Lett. 96, 075001 (2006) [5] C. Henning, M. Bonitz, A. Piel, P. Ludwig, H. Baumgartner, V. Golubnichiy, and D. Block, submitted to Phys. Rev. E. ...
Physical Review Letters, 1993
Journal of Experimental and Theoretical Physics, 2003
The internal energy of high-density hydrogen plasmas in the temperature range T = 10000-50000 K i... more The internal energy of high-density hydrogen plasmas in the temperature range T = 10000-50000 K is calculated by two different analytic approximation schemes-the method of an effective ion-ion interaction potential and the Padé approach within the chemical picture-and are compared with direct path integral Monte Carlo results. A reasonable agreement between the results obtained from the three independent calculations is found and the reasons for still existing differences are investigated. Interesting high-density phenomena such as the onset of ion crystallization are discussed.
Physical Review B
The time evolution in quantum many-body systems after external excitations is attracting high int... more The time evolution in quantum many-body systems after external excitations is attracting high interest in many fields, including dense plasmas, correlated solids, laser-excited materials, or fermionic and bosonic atoms in optical lattices. The theoretical modeling of these processes is challenging, and the only rigorous quantum-dynamics approach that can treat correlated fermions in two and three dimensions is nonequilibrium Green functions (NEGF). However, NEGF simulations are computationally expensive due to their T 3 scaling with the simulation duration T . Recently, T 2 scaling was achieved with the generalized Kadanoff-Baym ansatz (GKBA), for the second-order Born (SOA) self energy, which has substantially extended the scope of NEGF simulations. In a recent Letter [Schlünzen et al., Phys. Rev. Lett. 124, 076601 (2020)]. we demonstrated that GKBA-NEGF simulations can be efficiently mapped onto coupled time-local equations for the single-particle and two-particle Green functions on the time diagonal, hence the method has been called the G1-G2 scheme. This allows one to perform the same simulations with order T 1 scaling, both for SOA and GW self energies giving rise to a dramatic speedup. Here we present more details on the G1-G2 scheme, including derivations of the basic equations including results for a general basis, for Hubbard systems, and for jellium. Also, we demonstrate how to incorporate initial correlations into the G1-G2 scheme. Further, the derivations are extended to a broader class of self energies, including the T matrix in the particle-particle and particle-hole channels and the dynamically-screened-ladder approximation. Finally, we demonstrate that, for all self energies, the CPU-time scaling of the G1-G2 scheme with the basis dimension N b can be improved compared to our first report: The overhead compared to the original GKBA is not more than an additional factor N b , even for Hubbard systems.
physica status solidi (b)
physica status solidi (b)
Strongly correlated systems of fermions have an interesting phase diagram arising from the Hubbar... more Strongly correlated systems of fermions have an interesting phase diagram arising from the Hubbard gap. Excitation across the gap leads to the formation of doubly occupied lattice sites (doublons) which offers interesting electronic and optical properties. Moreover, when the system is driven out of equilibrium interesting collective dynamics may arise that are related to the spatial propagation of doublons. Here, a novel mechanism that was recently proposed by us [Balzer et al., submitted for publication, arXiv:1801.05267] is verified by exact diagonalization and nonequilibrium Green functions (NEGF) simulations-fermionic doublon creation by the impact of energetic ions. We report the formation of a nonequilibrium steady state with homogeneous doublon distribution. The effect should be particularly important for strongly correlated finite systems, such as graphene nanoribbons, and directly observable with fermionic atoms in optical lattices. We demonstrate that doublon formation and propagation in correlated lattice systems can be accurately simulated with NEGF. In addition to two-time results we present single-time results within the generalized Kadanoff-Baym ansatz (GKBA) with Hartree-Fock propagators (HF-GKBA). Finally we discuss systematic improvements of the GKBA that use correlated propagators (correlated GKBA) and a correlated initial state. Copyright line will be provided by the publisher Copyright line will be provided by the publisher arXiv:1808.07868v2 [cond-mat.str-el] 19 Sep 2018 : . . . U J J J J Γ(t)
Physical Review Letters
Strongly correlated systems of fermions have a number of exciting collective properties. Among th... more Strongly correlated systems of fermions have a number of exciting collective properties. Among them, the creation of a lattice that is occupied by doublons, i.e. two quantum particles with opposite spins, offers interesting electronic properties. In the past a variety of methods have been proposed to control doublon formation, both, spatially and temporally. Here, a novel mechanism is proposed and verified by exact diagonalization and nonequilibrium Green functions simulations-fermionic doublon creation by the impact of energetic ions. We report the formation of a nonequilibrium steady state with homogeneous doublon distribution. The effect should be observable in strongly correlated solids in contact with a high-pressure plasma and in fermionic atoms in optical lattices. PACS numbers: 71.30.+h, 05.30.Fk, 78.47.J-Strongly correlated systems are attracting increasing interest in many fields including dense plasmas [1], warm dense matter [2], dusty plasmas [3] and ultracold atoms [4]
Physical review letters, Jan 29, 2017
In a recent Letter [T. Dornheim et al., Phys. Rev. Lett. 117, 156403 (2016)PRLTAO0031-900710.1103... more In a recent Letter [T. Dornheim et al., Phys. Rev. Lett. 117, 156403 (2016)PRLTAO0031-900710.1103/PhysRevLett.117.156403], we presented the first quantum Monte Carlo (QMC) results for the warm dense electron gas in the thermodynamic limit. However, a complete parametrization of the exchange-correlation free energy with respect to density, temperature, and spin polarization remained out of reach due to the absence of (i) accurate QMC results below θ=k_{B}T/E_{F}=0.5 and (ii) QMC results for spin polarizations different from the paramagnetic case. Here we overcome both remaining limitations. By closing the gap to the ground state and by performing extensive QMC simulations for different spin polarizations, we are able to obtain the first completely ab initio exchange-correlation free energy functional; the accuracy achieved is an unprecedented ∼0.3%. This also allows us to quantify the accuracy and systematic errors of various previous approximate functionals.
Contributions to Plasma Physics
ABSTRACT Linearized fluid equations for the collective modes of weakly inhomogeneous plasmas incl... more ABSTRACT Linearized fluid equations for the collective modes of weakly inhomogeneous plasmas including strong coupling effects are derived from a recent kinetic theory based on an extended Singwi-Tosi-Land-Sjölander (STLS) ansatz [H. Kählert, G. J. Kalman, and M. Bonitz, Phys. Rev. E 90, 011101(R) (2014)]. The equations are analogous to the equations of linearized elasticity theory with space dependent elastic moduli that correspond to those of a bulk system with the local fluid density. The identification of the latter as infinite-frequency elastic moduli shows that the present version of the extended STLS theory accounts for the elastic properties of the fluid but does not capture the viscous behavior. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Plasma Physics and Controlled Fusion
The electrostatic potential of a moving dust grain in a complex plasma with magnetized ions is co... more The electrostatic potential of a moving dust grain in a complex plasma with magnetized ions is computed using linear response theory, thereby extending our previous work for unmagnetized plasmas [P. Ludwig et al., New J. Phys. 14, 053016 (2012)]. In addition to the magnetic field, our approach accounts for a finite ion temperature as well as ion-neutral collisions. Our recently introduced code Kielstream is used for an efficient calculation of the dust potential. Increasing the magnetization of the ions, we find that the shape of the potential crucially depends on the Mach number M . In the regime of subsonic ion flow (M < 1), a strong magnetization gives rise to a potential distribution that is qualitatively different from the unmagnetized limit, while for M > 1 the magnetic field effectively suppresses the plasma wakefield.
Contributions to Plasma Physics
Transport properties of strongly correlated quantum systems are of central interest in condensed ... more Transport properties of strongly correlated quantum systems are of central interest in condensed matter, ultracold atoms and in dense plasmas. There, the proper treatment of strong correlations poses a great challenge to theory. Here, we apply a Nonequilibrium Green Functions approach using a lattice model as a basic system. This allow us to treat a finite spatially inhomogeneous system with an arbitrary nonequilibrium initial state. Placing all particles initially to one side of the system allows for a nonequilibrium study of diffusion. Strong correlation effects are incorporated via T-matrix selfenergies.
Physical Review E
Ultrafast relaxation and correlation buildup in an N-particle system can be described theoretical... more Ultrafast relaxation and correlation buildup in an N-particle system can be described theoretically using two completely different methods: mechanical equations of motion ͑molecular dynamics͒ and quantum-statistical models ͑Kadanoff-Baym equations͒. We propose to perform detailed quantitative comparisons of the two methods to obtain a powerful and unbiased tool for testing different approximations. Results of such comparison are presented for a weakly coupled electron gas, which show remarkable agreement. ͓S1063-651X͑97͒05907-2͔
Physical Review B
We present numerical results for the momentum-orientation relaxation of optically excited electro... more We present numerical results for the momentum-orientation relaxation of optically excited electron plasmas in bulk semiconductors. Our results are based on the full two-time Green's function approach for carrier-carrier scattering and are compared to the results obtained within the conventional quantum Boltzmann equation. Defining ''memory effects'' by this comparison, we find memory effects mainly to be differences in the time-scale of the relaxation process rather than distinct qualitative features. Within the limitations of our isotropic static screening model, we find that, in both approaches, an initial anisotropic and nonmonotonic distribution function relaxes in a three-stage process in which the distribution becomes monotonic before it loses its anisotropy.
Physical review letters, Jan 7, 2016
We perform ab initio quantum Monte Carlo (QMC) simulations of the warm dense uniform electron gas... more We perform ab initio quantum Monte Carlo (QMC) simulations of the warm dense uniform electron gas in the thermodynamic limit. By combining QMC data with the linear response theory, we are able to remove finite-size errors from the potential energy over the substantial parts of the warm dense regime, overcoming the deficiencies of the existing finite-size corrections by Brown et al. [Phys. Rev. Lett. 110, 146405 (2013)]. Extensive new QMC results for up to N=1000 electrons enable us to compute the potential energy V and the exchange-correlation free energy F_{xc} of the macroscopic electron gas with an unprecedented accuracy of |ΔV|/|V|,|ΔF_{xc}|/|F|_{xc}∼10^{-3}. A comparison of our new data to the recent parametrization of F_{xc} by Karasiev et al. [Phys. Rev. Lett. 112, 076403 (2014)] reveals significant deviations to the latter.
Detailed numerical results for the structural properties of three-dimensional classical Coulomb c... more Detailed numerical results for the structural properties of three-dimensional classical Coulomb clusters confined in a spherical parabolic trap are presented. Based on extensive high accuracy computer simulations the shell configurations and energies for particle numbers in the range 2leNle1602 \le N\le 1602leNle160 are reported. Further, the mean shell radii and shell widths are calculated.
A three-dimensional Yukawa liquid exhibits normal self-diffusion which is characterized by Fick&#... more A three-dimensional Yukawa liquid exhibits normal self-diffusion which is characterized by Fick's law and a time-independent diffusion coefficient D [1]. This quantity can be evaluated from the Einstein relation, D=/6t. If however the mean-squared displacement grows faster than linearly with time, the diffusion coefficient is not well defined and the systems exhibits superdiffusive behaviour. Recently, superdiffusion has been observed in two-dimensional Yukawa liquids [2]. In this contribution we enter into the question about the occurrence of superdiffusion in the transiton-region from a purely three-dimensional to a quasi 2D system where one dimension is confined [3,4]. [0pt] [1] H. Ohta and S. Hamaguchi, Phys. Plasmas 7, 4506 (2000) [0pt] [2] B. Liu and J. Goree, Phys. Rev. E 75, 016405 (2007) [0pt] [3] Z. Donk'o, P. Hartmann and G. J. Kalman, Phys. Rev. E 69, 065401 (2004) [0pt] [4] T. Ott, Z. Donk'o, P. Hartmann and M. Bonitz, Submitted to Phys. Rev. E.
The breathing mode is a fundamental normal mode present in Coulomb systems, and may have utility ... more The breathing mode is a fundamental normal mode present in Coulomb systems, and may have utility in identifying particle charge and the Debye length of certain systems. The question remains whether this mode can be extended to strongly coupled Yukawa balls [1]. These systems are characterized by particles confined within a parabolic potential well and interacting through a shielded Coulomb
Eprint Arxiv Physics 0110013, Oct 4, 2001
The internal energy of high-density hydrogen plasmas in the temperature range T = 10, 000 . . . 5... more The internal energy of high-density hydrogen plasmas in the temperature range T = 10, 000 . . . 50, 000K is calculated by two different analytical approximation schemes (method of effective ion-ion interaction potential -EIIP and Padé approach within the chemical picture -PACH) and compared with path integral Monte Carlo results. Reasonable agreement between the results obtained from the three independent calculations is found, the reasons for still existing differences is investigated. Interesting high density phenomena such as the formation of clusters and the onset of crystallization are discussed.
ABSTRACT Over the last two decades, the Quasi-Localized Charge Approximation (QLCA) has been succ... more ABSTRACT Over the last two decades, the Quasi-Localized Charge Approximation (QLCA) has been successfully applied to investigate the dielectric properties of various strongly coupled systems [1]. While these earlier studies focused on bulk properties, we are concerned with the application of the QLCA to finite inhomogeneous systems. These situations are commonly encountered in ion trap plasmas, ultra-cold neutral plasmas, or dusty plasmas. Starting from the microscopic Lagrangian, we derive an equation for the fluid displacement field and compare our results with previous calculations [2] and a theory for strongly correlated ion plasmas [3]. Since the QLCA accounts for correlation effects, it improves upon so-called ``cold-fluid'' theories and should allow to reduce the discrepancies between the latter and molecular dynamics simulations in a confined Yukawa plasma [4]. Here, we present our first results.[3pt] [1] K. I. Golden and G. J. Kalman, Phys. Plasmas 7, 14 (2000)[0pt] [2] C.-J. Lee and G. J. Kalman, J. Korean Phys. Soc. 58, 448 (2011)[0pt] [3] D. H. E. Dubin and J. P. Schiffer, Phys. Rev. E 53, 5249 (1996), D. H. E. Dubin, Phys. Rev. E 53, 5268 (1996)[0pt] [4] H. K"ahlert and M. Bonitz, Phys. Rev. E 83, 056401 (2011)
Dusty plasmas are a model system for studying strong correlation. The dust grains' size of a few ... more Dusty plasmas are a model system for studying strong correlation. The dust grains' size of a few micro-meters and their characteristic oscillation frequency of a few hertz allows for an investigation of many particle effects on an atomic level. In this article, we model the heat transport through an axially confined 2D dust cluster from the center to the outside. The system behaves particularly interesting since heat is not only conducted within the dust component but also transfered to the neutral gas. Fitting the analytical solution to the obtained radial temperature profiles allows to determine the heat conductivity kheat\kheatkheat. The heat conductivity is found to be constant over a wide range of coupling strengths even including the phase transition from solid to liquid here, as it was also found in extended systems by V. Nosenko et al. in 2008 \cite{PhysRevLett.100.025003}
Bulletin of the American …, 2006
... Rev. E 71, 046403 (2005) [4] M. Bonitz, D. Block, O. Arp, V. Golubnychiy, H. Baumgartner, P. ... more ... Rev. E 71, 046403 (2005) [4] M. Bonitz, D. Block, O. Arp, V. Golubnychiy, H. Baumgartner, P. Ludwig, A. Piel, and A. Filinov, Phys. Rev. Lett. 96, 075001 (2006) [5] C. Henning, M. Bonitz, A. Piel, P. Ludwig, H. Baumgartner, V. Golubnichiy, and D. Block, submitted to Phys. Rev. E. ...
Physical Review Letters, 1993
Journal of Experimental and Theoretical Physics, 2003
The internal energy of high-density hydrogen plasmas in the temperature range T = 10000-50000 K i... more The internal energy of high-density hydrogen plasmas in the temperature range T = 10000-50000 K is calculated by two different analytic approximation schemes-the method of an effective ion-ion interaction potential and the Padé approach within the chemical picture-and are compared with direct path integral Monte Carlo results. A reasonable agreement between the results obtained from the three independent calculations is found and the reasons for still existing differences are investigated. Interesting high-density phenomena such as the onset of ion crystallization are discussed.
Physical Review B
The time evolution in quantum many-body systems after external excitations is attracting high int... more The time evolution in quantum many-body systems after external excitations is attracting high interest in many fields, including dense plasmas, correlated solids, laser-excited materials, or fermionic and bosonic atoms in optical lattices. The theoretical modeling of these processes is challenging, and the only rigorous quantum-dynamics approach that can treat correlated fermions in two and three dimensions is nonequilibrium Green functions (NEGF). However, NEGF simulations are computationally expensive due to their T 3 scaling with the simulation duration T . Recently, T 2 scaling was achieved with the generalized Kadanoff-Baym ansatz (GKBA), for the second-order Born (SOA) self energy, which has substantially extended the scope of NEGF simulations. In a recent Letter [Schlünzen et al., Phys. Rev. Lett. 124, 076601 (2020)]. we demonstrated that GKBA-NEGF simulations can be efficiently mapped onto coupled time-local equations for the single-particle and two-particle Green functions on the time diagonal, hence the method has been called the G1-G2 scheme. This allows one to perform the same simulations with order T 1 scaling, both for SOA and GW self energies giving rise to a dramatic speedup. Here we present more details on the G1-G2 scheme, including derivations of the basic equations including results for a general basis, for Hubbard systems, and for jellium. Also, we demonstrate how to incorporate initial correlations into the G1-G2 scheme. Further, the derivations are extended to a broader class of self energies, including the T matrix in the particle-particle and particle-hole channels and the dynamically-screened-ladder approximation. Finally, we demonstrate that, for all self energies, the CPU-time scaling of the G1-G2 scheme with the basis dimension N b can be improved compared to our first report: The overhead compared to the original GKBA is not more than an additional factor N b , even for Hubbard systems.
physica status solidi (b)
physica status solidi (b)
Strongly correlated systems of fermions have an interesting phase diagram arising from the Hubbar... more Strongly correlated systems of fermions have an interesting phase diagram arising from the Hubbard gap. Excitation across the gap leads to the formation of doubly occupied lattice sites (doublons) which offers interesting electronic and optical properties. Moreover, when the system is driven out of equilibrium interesting collective dynamics may arise that are related to the spatial propagation of doublons. Here, a novel mechanism that was recently proposed by us [Balzer et al., submitted for publication, arXiv:1801.05267] is verified by exact diagonalization and nonequilibrium Green functions (NEGF) simulations-fermionic doublon creation by the impact of energetic ions. We report the formation of a nonequilibrium steady state with homogeneous doublon distribution. The effect should be particularly important for strongly correlated finite systems, such as graphene nanoribbons, and directly observable with fermionic atoms in optical lattices. We demonstrate that doublon formation and propagation in correlated lattice systems can be accurately simulated with NEGF. In addition to two-time results we present single-time results within the generalized Kadanoff-Baym ansatz (GKBA) with Hartree-Fock propagators (HF-GKBA). Finally we discuss systematic improvements of the GKBA that use correlated propagators (correlated GKBA) and a correlated initial state. Copyright line will be provided by the publisher Copyright line will be provided by the publisher arXiv:1808.07868v2 [cond-mat.str-el] 19 Sep 2018 : . . . U J J J J Γ(t)
Physical Review Letters
Strongly correlated systems of fermions have a number of exciting collective properties. Among th... more Strongly correlated systems of fermions have a number of exciting collective properties. Among them, the creation of a lattice that is occupied by doublons, i.e. two quantum particles with opposite spins, offers interesting electronic properties. In the past a variety of methods have been proposed to control doublon formation, both, spatially and temporally. Here, a novel mechanism is proposed and verified by exact diagonalization and nonequilibrium Green functions simulations-fermionic doublon creation by the impact of energetic ions. We report the formation of a nonequilibrium steady state with homogeneous doublon distribution. The effect should be observable in strongly correlated solids in contact with a high-pressure plasma and in fermionic atoms in optical lattices. PACS numbers: 71.30.+h, 05.30.Fk, 78.47.J-Strongly correlated systems are attracting increasing interest in many fields including dense plasmas [1], warm dense matter [2], dusty plasmas [3] and ultracold atoms [4]
Physical review letters, Jan 29, 2017
In a recent Letter [T. Dornheim et al., Phys. Rev. Lett. 117, 156403 (2016)PRLTAO0031-900710.1103... more In a recent Letter [T. Dornheim et al., Phys. Rev. Lett. 117, 156403 (2016)PRLTAO0031-900710.1103/PhysRevLett.117.156403], we presented the first quantum Monte Carlo (QMC) results for the warm dense electron gas in the thermodynamic limit. However, a complete parametrization of the exchange-correlation free energy with respect to density, temperature, and spin polarization remained out of reach due to the absence of (i) accurate QMC results below θ=k_{B}T/E_{F}=0.5 and (ii) QMC results for spin polarizations different from the paramagnetic case. Here we overcome both remaining limitations. By closing the gap to the ground state and by performing extensive QMC simulations for different spin polarizations, we are able to obtain the first completely ab initio exchange-correlation free energy functional; the accuracy achieved is an unprecedented ∼0.3%. This also allows us to quantify the accuracy and systematic errors of various previous approximate functionals.
Contributions to Plasma Physics
ABSTRACT Linearized fluid equations for the collective modes of weakly inhomogeneous plasmas incl... more ABSTRACT Linearized fluid equations for the collective modes of weakly inhomogeneous plasmas including strong coupling effects are derived from a recent kinetic theory based on an extended Singwi-Tosi-Land-Sjölander (STLS) ansatz [H. Kählert, G. J. Kalman, and M. Bonitz, Phys. Rev. E 90, 011101(R) (2014)]. The equations are analogous to the equations of linearized elasticity theory with space dependent elastic moduli that correspond to those of a bulk system with the local fluid density. The identification of the latter as infinite-frequency elastic moduli shows that the present version of the extended STLS theory accounts for the elastic properties of the fluid but does not capture the viscous behavior. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Plasma Physics and Controlled Fusion
The electrostatic potential of a moving dust grain in a complex plasma with magnetized ions is co... more The electrostatic potential of a moving dust grain in a complex plasma with magnetized ions is computed using linear response theory, thereby extending our previous work for unmagnetized plasmas [P. Ludwig et al., New J. Phys. 14, 053016 (2012)]. In addition to the magnetic field, our approach accounts for a finite ion temperature as well as ion-neutral collisions. Our recently introduced code Kielstream is used for an efficient calculation of the dust potential. Increasing the magnetization of the ions, we find that the shape of the potential crucially depends on the Mach number M . In the regime of subsonic ion flow (M < 1), a strong magnetization gives rise to a potential distribution that is qualitatively different from the unmagnetized limit, while for M > 1 the magnetic field effectively suppresses the plasma wakefield.
Contributions to Plasma Physics
Transport properties of strongly correlated quantum systems are of central interest in condensed ... more Transport properties of strongly correlated quantum systems are of central interest in condensed matter, ultracold atoms and in dense plasmas. There, the proper treatment of strong correlations poses a great challenge to theory. Here, we apply a Nonequilibrium Green Functions approach using a lattice model as a basic system. This allow us to treat a finite spatially inhomogeneous system with an arbitrary nonequilibrium initial state. Placing all particles initially to one side of the system allows for a nonequilibrium study of diffusion. Strong correlation effects are incorporated via T-matrix selfenergies.
Physical Review E
Ultrafast relaxation and correlation buildup in an N-particle system can be described theoretical... more Ultrafast relaxation and correlation buildup in an N-particle system can be described theoretically using two completely different methods: mechanical equations of motion ͑molecular dynamics͒ and quantum-statistical models ͑Kadanoff-Baym equations͒. We propose to perform detailed quantitative comparisons of the two methods to obtain a powerful and unbiased tool for testing different approximations. Results of such comparison are presented for a weakly coupled electron gas, which show remarkable agreement. ͓S1063-651X͑97͒05907-2͔
Physical Review B
We present numerical results for the momentum-orientation relaxation of optically excited electro... more We present numerical results for the momentum-orientation relaxation of optically excited electron plasmas in bulk semiconductors. Our results are based on the full two-time Green's function approach for carrier-carrier scattering and are compared to the results obtained within the conventional quantum Boltzmann equation. Defining ''memory effects'' by this comparison, we find memory effects mainly to be differences in the time-scale of the relaxation process rather than distinct qualitative features. Within the limitations of our isotropic static screening model, we find that, in both approaches, an initial anisotropic and nonmonotonic distribution function relaxes in a three-stage process in which the distribution becomes monotonic before it loses its anisotropy.
Physical review letters, Jan 7, 2016
We perform ab initio quantum Monte Carlo (QMC) simulations of the warm dense uniform electron gas... more We perform ab initio quantum Monte Carlo (QMC) simulations of the warm dense uniform electron gas in the thermodynamic limit. By combining QMC data with the linear response theory, we are able to remove finite-size errors from the potential energy over the substantial parts of the warm dense regime, overcoming the deficiencies of the existing finite-size corrections by Brown et al. [Phys. Rev. Lett. 110, 146405 (2013)]. Extensive new QMC results for up to N=1000 electrons enable us to compute the potential energy V and the exchange-correlation free energy F_{xc} of the macroscopic electron gas with an unprecedented accuracy of |ΔV|/|V|,|ΔF_{xc}|/|F|_{xc}∼10^{-3}. A comparison of our new data to the recent parametrization of F_{xc} by Karasiev et al. [Phys. Rev. Lett. 112, 076403 (2014)] reveals significant deviations to the latter.
Detailed numerical results for the structural properties of three-dimensional classical Coulomb c... more Detailed numerical results for the structural properties of three-dimensional classical Coulomb clusters confined in a spherical parabolic trap are presented. Based on extensive high accuracy computer simulations the shell configurations and energies for particle numbers in the range 2leNle1602 \le N\le 1602leNle160 are reported. Further, the mean shell radii and shell widths are calculated.
A three-dimensional Yukawa liquid exhibits normal self-diffusion which is characterized by Fick&#... more A three-dimensional Yukawa liquid exhibits normal self-diffusion which is characterized by Fick's law and a time-independent diffusion coefficient D [1]. This quantity can be evaluated from the Einstein relation, D=/6t. If however the mean-squared displacement grows faster than linearly with time, the diffusion coefficient is not well defined and the systems exhibits superdiffusive behaviour. Recently, superdiffusion has been observed in two-dimensional Yukawa liquids [2]. In this contribution we enter into the question about the occurrence of superdiffusion in the transiton-region from a purely three-dimensional to a quasi 2D system where one dimension is confined [3,4]. [0pt] [1] H. Ohta and S. Hamaguchi, Phys. Plasmas 7, 4506 (2000) [0pt] [2] B. Liu and J. Goree, Phys. Rev. E 75, 016405 (2007) [0pt] [3] Z. Donk'o, P. Hartmann and G. J. Kalman, Phys. Rev. E 69, 065401 (2004) [0pt] [4] T. Ott, Z. Donk'o, P. Hartmann and M. Bonitz, Submitted to Phys. Rev. E.
The breathing mode is a fundamental normal mode present in Coulomb systems, and may have utility ... more The breathing mode is a fundamental normal mode present in Coulomb systems, and may have utility in identifying particle charge and the Debye length of certain systems. The question remains whether this mode can be extended to strongly coupled Yukawa balls [1]. These systems are characterized by particles confined within a parabolic potential well and interacting through a shielded Coulomb
Eprint Arxiv Physics 0110013, Oct 4, 2001
The internal energy of high-density hydrogen plasmas in the temperature range T = 10, 000 . . . 5... more The internal energy of high-density hydrogen plasmas in the temperature range T = 10, 000 . . . 50, 000K is calculated by two different analytical approximation schemes (method of effective ion-ion interaction potential -EIIP and Padé approach within the chemical picture -PACH) and compared with path integral Monte Carlo results. Reasonable agreement between the results obtained from the three independent calculations is found, the reasons for still existing differences is investigated. Interesting high density phenomena such as the formation of clusters and the onset of crystallization are discussed.
ABSTRACT Over the last two decades, the Quasi-Localized Charge Approximation (QLCA) has been succ... more ABSTRACT Over the last two decades, the Quasi-Localized Charge Approximation (QLCA) has been successfully applied to investigate the dielectric properties of various strongly coupled systems [1]. While these earlier studies focused on bulk properties, we are concerned with the application of the QLCA to finite inhomogeneous systems. These situations are commonly encountered in ion trap plasmas, ultra-cold neutral plasmas, or dusty plasmas. Starting from the microscopic Lagrangian, we derive an equation for the fluid displacement field and compare our results with previous calculations [2] and a theory for strongly correlated ion plasmas [3]. Since the QLCA accounts for correlation effects, it improves upon so-called ``cold-fluid'' theories and should allow to reduce the discrepancies between the latter and molecular dynamics simulations in a confined Yukawa plasma [4]. Here, we present our first results.[3pt] [1] K. I. Golden and G. J. Kalman, Phys. Plasmas 7, 14 (2000)[0pt] [2] C.-J. Lee and G. J. Kalman, J. Korean Phys. Soc. 58, 448 (2011)[0pt] [3] D. H. E. Dubin and J. P. Schiffer, Phys. Rev. E 53, 5249 (1996), D. H. E. Dubin, Phys. Rev. E 53, 5268 (1996)[0pt] [4] H. K"ahlert and M. Bonitz, Phys. Rev. E 83, 056401 (2011)
Dusty plasmas are a model system for studying strong correlation. The dust grains' size of a few ... more Dusty plasmas are a model system for studying strong correlation. The dust grains' size of a few micro-meters and their characteristic oscillation frequency of a few hertz allows for an investigation of many particle effects on an atomic level. In this article, we model the heat transport through an axially confined 2D dust cluster from the center to the outside. The system behaves particularly interesting since heat is not only conducted within the dust component but also transfered to the neutral gas. Fitting the analytical solution to the obtained radial temperature profiles allows to determine the heat conductivity kheat\kheatkheat. The heat conductivity is found to be constant over a wide range of coupling strengths even including the phase transition from solid to liquid here, as it was also found in extended systems by V. Nosenko et al. in 2008 \cite{PhysRevLett.100.025003}