15 research outputs found
Two ground-state modifications of quantum-dot beryllium
Exact electronic properties of a system of four Coulomb-interacting
two-dimensional electrons in a parabolic confinement are reported. We show that
degenerate ground states of this system are characterized by qualitatively
different internal electron-electron correlations, and that the formation of
Wigner molecule in the strong-interaction regime is going on in essentially
different ways in these ground states.Comment: 5 pages, incl 5 Figures and 2 Table
Quantum dots in magnetic fields: thermal response of broken symmetry phases
We investigate the thermal properties of circular semiconductor quantum dots
in high magnetic fields using finite temperature Hartree-Fock techniques. We
demonstrate that for a given magnetic field strength quantum dots undergo
various shape phase transitions as a function of temperature, and we outline
possible observable consequences.Comment: In Press, Phys. Rev. B (2001
Roto-vibrational spectrum and Wigner crystallization in two-electron parabolic quantum dots
We provide a quantitative determination of the crystallization onset for two
electrons in a parabolic two-dimensional confinement. This system is shown to
be well described by a roto-vibrational model, Wigner crystallization occurring
when the rotational motion gets decoupled from the vibrational one. The Wigner
molecule thus formed is characterized by its moment of inertia and by the
corresponding sequence of rotational excited states. The role of a vertical
magnetic field is also considered. Additional support to the analysis is given
by the Hartree-Fock phase diagram for the ground state and by the random-phase
approximation for the moment of inertia and vibron excitations.Comment: 10 pages, 8 figures, replaced by the published versio
Quantum dots in high magnetic fields: Rotating-Wigner-molecule versus composite-fermion approach
Exact diagonalization results are reported for the lowest rotational band of
N=6 electrons in strong magnetic fields in the range of high angular momenta 70
<= L <= 140 (covering the corresponding range of fractional filling factors 1/5
>= nu >= 1/9). A detailed comparison of energetic, spectral, and transport
properties (specifically, magic angular momenta, radial electron densities,
occupation number distributions, overlaps and total energies, and exponents of
current-voltage power law) shows that the recently discovered
rotating-electron-molecule wave functions [Phys. Rev. B 66, 115315 (2002)]
provide a superior description compared to the
composite-fermion/Jastrow-Laughlin ones.Comment: Extensive clarifications were added (see new footnotes) regarding the
difference between the rotating Wigner molecule and the bulk Wigner crystal;
also regarding the influence of an external confining potential. 12 pages.
Revtex4 with 6 EPS figures and 5 tables . For related papers, see
http://www.prism.gatech.edu/~ph274c
Topological Defects and Non-homogeneous Melting of Large 2D Coulomb Clusters
The configurational and melting properties of large two-dimensional clusters
of charged classical particles interacting with each other via the Coulomb
potential are investigated through the Monte Carlo simulation technique. The
particles are confined by a harmonic potential. For a large number of particles
in the cluster (N>150) the configuration is determined by two competing
effects, namely in the center a hexagonal lattice is formed, which is the
groundstate for an infinite 2D system, and the confinement which imposes its
circular symmetry on the outer edge. As a result a hexagonal Wigner lattice is
formed in the central area while at the border of the cluster the particles are
arranged in rings. In the transition region defects appear as dislocations and
disclinations at the six corners of the hexagonal-shaped inner domain. Many
different arrangements and type of defects are possible as metastable
configurations with a slightly higher energy. The particles motion is found to
be strongly related to the topological structure. Our results clearly show that
the melting of the clusters starts near the geometry induced defects, and that
three different melting temperatures can be defined corresponding to the
melting of different regions in the cluster.Comment: 7 pages, 11 figures, submitted to Phys. Rev.
Strongly correlated quantum dots in weak confinement potentials and magnetic fields
We explore a strongly correlated quantum dot in the presence of a weak
confinement potential and a weak magnetic field. Our exact diagonalization
studies show that the groundstate property of such a quantum dot is rather
sensitive to the magnetic field and the strength of the confinement potential.
We have determined rich phase diagrams of these quantum dots. Some experimental
consequences of the obtained phase diagrams are discussed.Comment: 5 pages, 7 figures, new and updated figure
Group theoretical analysis of symmetry breaking in two-dimensional quantum dots
We present a group theoretical study of the symmetry-broken unrestricted
Hartree-Fock orbitals and electron densities in the case of a two-dimensional
N-electron single quantum dot (with and without an external magnetic field).
The breaking of rotational symmetry results in canonical orbitals that (1) are
associated with the eigenvectors of a Hueckel hamiltonian having sites at the
positions determined by the equilibrium molecular configuration of the
classical N-electron problem, and (2) transform according to the irreducible
representations of the point group specified by the discrete symmetries of this
classical molecular configuration. Through restoration of the total-spin and
rotational symmetries via projection techniques, we show that the point-group
discrete symmetry of the unrestricted Hartree-Fock wave function underlies the
appearance of magic angular momenta (familiar from exact-diagonalization
studies) in the excitation spectra of the quantum dot. Furthermore, this
two-step symmetry-breaking/symmetry-restoration method accurately describes the
energy spectra associated with the magic angular momenta.Comment: A section VI.B entitled "Quantitative description of the lowest
rotational band" has been added. 16 pages. Revtex with 10 EPS figures. A
version of the manuscript with high quality figures is available at
http://calcite.physics.gatech.edu/~costas/uhf_group.html For related papers,
see http://www.prism.gatech.edu/~ph274c
Static and dynamic structure factors with account of the ion structure for high-temperature alkali and alkaline earth plasmas
The electron-electron, electron-ion, ion-ion and charge-charge static structure factors are calculated for alkali (at T = 30 000 K, 60 000 K, n (e) = 0.7 x 10(21) A center dot 1.1 x 10(22) cm(-3)) and Be2+ (at T = 20 eV, n (e) = 2.5 x 10(23) cm(-3)) plasmas using the method described by Gregori et al. The dynamic structure factors for alkali plasmas are calculated at T = 30 000 K, n (e) = 1.74 x 10(20), 1.11 x 10(22) cm(-3) using the method of moments developed by Adamjan et al. In both methods the screened Hellmann-Gurskii-Krasko potential, obtained on the basis of Bogolyubov's method, has been used taking into account not only the quantum-mechanical effects but also the repulsion due to the Pauli exclusion principle. The repulsive part of the Hellmann-Gurskii-Krasko (HGK) potential reflects important features of the ion structure. Our results on the static structure factors for Be2+ plasma deviate from the data obtained by Gregori et al., while our dynamic structure factors are in a reasonable agreement with those of Adamyan et al.: at higher values of k and with increasing k the curves damp down while at lower values of k, and especially at higher electron coupling, we observe sharp peaks also reported in the mentioned work. For lower electron coupling the dynamic structure factors of Li+, Na+, K+, Rb+ and Cs+ do not differ while at higher electron coupling these curves split. As the number of shell electrons increases from Li+ to Cs+ the curves shift in the direction of low absolute value of omega and their heights diminish. We conclude that the short range forces, which we take into account by means of the HGK model potential, which deviates from the Coulomb and Deutsch ones, influence the static and dynamic structure factors significantly.The work has been realised at the Humboldt University at Berlin (Germany). One of the authors (S. P. Sadykova) would like to express sincere thanks to the Erasmus Mundus Program of the EU for the financial support and especially to Mr. M. Parske for his aid, to the Institute of Physics, Humboldt University at Berlin, for the support which made her participation at some scientific Conferences possible; I. M. T. acknowledges the financial support of the Spanish Ministerio de Educacion y Ciencia Project No. ENE2007-67406-C02-02/FTN and valuable discussions with Dr. D. Gericke.Sadykova, SP.; Ebeling, W.; Tkachenko Gorski, IM. (2011). Static and dynamic structure factors with account of the ion structure for high-temperature alkali and alkaline earth plasmas. European Physical Journal D. 61(1):117-130. https://doi.org/10.1140/epjd/e2010-10118-yS117130611G. Gregori, O.L. Landen, S.H. Glenzer, Phys. Rev. E 74, 026402 (2006)G. Gregori, A. Ravasio, A. Höll, S.H. Glenzer, S.J. Rose, High Energy Density Physics 3, 99 (2007)V.M. Adamyan, I.M. Tkachenko, Teplofiz. Vys. Temp. 21, 417 (1983) [High Temp. (USA) 21, 307 (1983)]V.M. Adamyan, T. Meyer, I.M. Tkachenko, Fiz. Plazmy 11, 826 (1985) [Sov. J. Plasma Phys. 11, 481 (1985)]S.V. Adamjan, I.M. Tkachenko, J.L. Muñoz-Cobo, G. Verdú MartÃn, Phys. Rev. E 48, 2067 (1993)V.M. Adamyan, I.M. Tkachenko, Contrib. Plasma Phys. 43, 252 (2003)S. Sadykova, W. Ebeling, I. Valuev, I. Sokolov, Contrib. Plasma Phys. 49, 76 (2009)M.J. Rosseinsky, K. Prassides, Nature 464, 39 (2010)Physics and Chemistry of Alkali Metal Adsorption, edited by H.P. Bonzel, A.M. Bradshaw, G. Ertl (Elsevier, Amsterdam, 1989), Materials Science Monographs, Vol. 57A.N. Klyucharev, N.N. Bezuglov, A.A. Matveev, A.A. Mihajlov, Lj.M. Ignjatović, M.S. Dimitrijević, New Astron. Rev. 51, 547 (2007)F. Hensel, Liquid Metals, edited by R. Evans, D.A. Greenwood, IOP Conf. Ser. No. 30 (IPPS, London, 1977)F. Hensel, S. Juengst, F. Noll, R. Winter, In Localisation and Metal Insulator Transitions, edited by D. Adler, H. Fritsche (Plenum Press, New York, 1985)N.F. Mott, Metal-Insulator Transitions (Taylor and Francis, London, 1974)H. Hess, Physics of nonideal plasmas, edited by W. Ebeling, A. Foerster, R. Radtke, B.G. Teubner (Leipzig, 1992)V. Sizyuk, A. Hassanein, T. Sizyuk, J. Appl. Phys. 100, 103106 (2006)S. Sadykova, W. Ebeling, I. Valuev, I. Sokolov, Contrib. Plasma Phys. 49, 388 (2009)H. Ebert, Physikalisches Taschenbuch (F. Vieweg & Sohn, Braunschweig, 1967)S.H. Glenzer, G. Gregori, R.W. Lee, F.J. Rogers, S.W. Pollaine, O.L. Landen, Phys. Rev. Lett. 90, 175002 (2003)G. Gregori, S.H. Glenzer, H.-K. Chung, D.H. Froula, R.W. Lee, N.B. Meezan, J.D. Moody, C. Niemann, O.L. Landen, B. Holst, R. Redmer, S.P. Regan, H. Sawada, J. Quant. Spectrosc. Radiat. Transfer 99, 225237 (2006)D. Riley, N.C. Woolsey, D. McSherry, I. Weaver, A. Djaoui, E. Nardi, Phys. Rev. Lett. 84, 1704 (2000)S.H. Glenzer, Phys. Rev. Lett. 98, 065002 (2007)J. Sheffield, Plasma Scattering of Electromagnetic Radiation (Academic Press, New York, 1975)A. Höll, Th. Bornath, L. Cao, T. Döppner, S. Düsterer, E. Föster, C. Fortmann, S.H. Glenzer, G. Gregori, T. Laarmann, K.-H. Meiwes-Broer, A. Przystawik, P. Radcliffe, R. Redmer, H. Reinholz, G. Röpke, R. Thiele, J. Tiggesbäumker, S. Toleikis, N.X. Truong, T. Tschentscher, I. Ushmann, U. Zastrau, High Energy Density Phys. 3, 120 (2007)Yu.V. Arkhipov, A. Askaruly, D. Ballester, A.E. Davletov, G.M. Meirkhanova, I.M. Tkachenko, Phys. Rev. E 76, 026403 (2007)Yu.V. Arkhipov, A. Askaruly, D. Ballester, A.E. Davletov, I.M. Tkachenko, G. Zwicknagel, Phys. Rev. E 81, 026402 (2010)J.P. Hansen, I.R. Mc. Donald, Phys. Rev. A 23, 2041 (1981)J.P. Hansen, E.L. Polock, I.R. McDonald, Phys. Rev. Lett. 32, 277 (1974)V. Schwarz, B. Holst, T. Bornath, C. Fortmann, W-D. Kraeft, R. Thiele, R. Redmer, G. Gregori, H. Ja Leed, T. Döppner, S.H. Glenzer, High Energy Density Phys. 5, 1 (2009)D.O. Gericke, K. Wünsch, J. Vorberger, Nucl. Instrum. Methods Phys. Res. A 606, 142 (2009)B. Bernu, D. Ceperley, Quantum Monte Carlo Methods in Physics and Chemistry, edited by M.P. Nightingale, C. Umrigar (Kluwer Academic Publishers, Boston, 1999), NATO ASI Series, Series C, Mathematical and Physical Sciences, Vol. C-525G. Kelbg, Ann. Physik 13 354 (1964)C. Deutsch, Phys. Lett. A 60, 317 (1977)H. Minoo, M.M. Gombert, C. Deutsch, Phys. Rev. A 23, 924 (1981)W. Ebeling, G.E. Norman, A.A. Valuev, I. Valuev, Contrib. Plasma Phys. 39, 61 (1999)A.V. Filinov, M. Bonitz, W. Ebeling, J. Phys. A. 36, 5957 (2003)H. Hellmann, J. Chem. Phys. 3, 61 (1935)H. Hellmann, Acta Fizicochem. USSR 1, 913 (1935)H. Hellmann, Acta Fizicochem. USSR 4, 225 (1936)H. Hellmann, W. Kassatotschkin, Acta Fizicochem. USSR 5, 23 (1936)W.A. Harrison, Pseudopotentials in the Theory of Metals (Benjamin, New York, 1966)V. Heine, M.L. Cohen, D. Weaire, Psevdopotenzcial'naya Teoriya (Mir, Moskva, 1973)V. Heine, The pseudopotential concept, edited by H. Ehrenreich, F. Seitz, D. Turnbull, Solid State Physics 24, 1 (Academic, New York 1970)G.L. Krasko, Z.A. Gurskii, JETP Lett. 9, 363 (1969)W. Ebeling, W.-D. Kraeft, D. Kremp, Theory of Bound State and Ionization Equilibrium in Plasmas and Solids (Akademie-Verlag, Berlin, 1976)W. Zimdahl, W. Ebeling, Ann. Phys. (Leipzig) 34, 9 (1977)W. Ebeling, C.-V. Meister, R. Saendig, 13 ICPIG (Berlin, 1977) 725W. Ebeling, C.V. Meister, R. Saendig, W.-D. Kraeft, Ann. Phys. 491, 321 (1979)N.N. Bogolyubov, Dynamical Theory Problems in Statistical Physics (in Russian) (GITTL, Moscow, 1946)N.N. Bogolyubov, Studies in Statistical Mechanics, Engl. Transl., edited by J. De Boer, G.E. Uhlenbeck (North-Holland, Amsterdam, 1962)H. Falkenhagen, Theorie der Elektrolyte (S. Hirzel Verlag, Leipzig, 1971), p. 369Yu.V. Arkhipov, F.B. Baimbetov, A.E. Davletov, Eur. Phys. J. D 8, 299 (2000)P. Seuferling, J. Vogel, C. Toepffer, Phys. Rev. A 40, 323 (1989)L. Szasz, Pseudopotential Theory of Atoms and Molecules (Wiley-Intersc., New York, 1985)W.H.E. Schwarz, Acta Phys. Hung. 27, 391 (1969)W.H.E. Schwarz, Theor. Chim. Acta 11, 307 (1968)N.P. Kovalenko, Yu.P. Krasnyj, U. Krey, Physics of Amorphous Metalls (Wiley-VCH, Weinheim, 2001)Z.A. Gurski, G.L. Krasko, Doklady Akademii Nauk SSSR (in Russian) 197, 810 (1971)C. Fiolhais, J.P. Perdew, S.Q. Armster, J.M. MacLaren, Phys. Rev. B 51, 14001 (1995)S.S. Dalgic, S. Dalgic, G. Tezgor, Phys. Chem. Liq. 40, 539, (2002)E.M. Apfelbaum, Phys. Chem. Liq., 48, 534 (2010)Yu.V. Arkhipov, A.E. Davletov, Phys. Lett. A 247, 339 (1998)W. Ebeling, J. Ortner, Physica Scripta T 75, 93 (1998)J. Ortner, F. Schautz, W. Ebeling, Phys. Rev. E 56, 4665 (1997)N.I. Akhieser, The classical Moment Problem (Oliver and Boyd, London, 1965)M.G. Krein, A.A. Nudel'man, The Markov Moment Problem and External Problems (American Mathematical Society, Translations, New York, 1977)M.J. Corbatón, I.M. Tkachenko, Int. Conference on Strongly Coupled Coulomb Systems (SCCS2008), Camerino, Italy, July-August, 2008, Book of Abstracts, p. 90V.M. Adamyan, A.A. Mihajlov, N.M. Sakan, V.A. Srećković, I.M. Tkachenko, J. Phys. A: Math. Theor. 42, 214005 (2009)S. Ichimaru, Statistical Plasma Physics, Vol. I: Basic Principles (Addison-Wesley, Redwood City, 1992)W. Ebeling, A. Foerster, W. Richert, H. Hess, Physics A 150, 159 (1988)H. Wagenknecht, W. Ebeling, A. Förster, Contrib. Plasma Phys. 41, 15 (2001