Speaker
Constantine Yannouleas
Description
The physics of condensed-matter nanosystems exhibits
remarkable analogies with atomic nuclei. Examples are:
Plasmons corresponding to Giant resonances [1], electronic
shells, de- formed shapes, and fission [2], beta-type decay,
strongly correlated phenomena associated with symmetry
breaking and symmetry restoration [3], etc. Most recently,
analogies with relativistic quantum-field theories (RQFT) and
high-energy particle physics are beeing explored in the
field of graphene nanostructures [4]. The talk will review
these analogies focusing in particular on the following
three aspects:
(1) The shell-correction method (SCM, commonly known as
Strutinsky’s averaging method and introduced in the 1960’s
in nuclear physics) was formulated [5] in the context of
density functional theory (DFT). Applications of the DFT-SCM
(and of a semiempirical variant, SE-SCM, closer to the
nuclear Strutinsky approach) to condensed-matter finite
systems will be discussed, including the charging and
fragmentation of metal clusters, fullerenes, and metallic
nanowires [5]. The DFT-SCM offers an improvement compared to
the use of Thomas-Fermi gradient expansions for the kinetic
energy density functional in the framework of
orbital-free DFT.
(2) A unified description of strongly correlated phenomena
in finite systems of repelling particles [whether electrons
in quantum dots (QDs) or ultracold bosons in rotating traps]
has been achieved through a two-step method of symmetry
breaking at the unrestricted Hartree- Fock (UHF) level and
of subsequent symmetry restoration via post Hartree-Fock
projection techniques [3]. The general principles of the
two-step method can be traced to nuclear theory (Peierls and
Yoccoz) and quantum chemistry (L ̈owdin). This method can
describe a wide variety of novel strongly correlated
phenomena, including:
(I) Chemical bonding and dissociation in quantum dot
molecules and in single elliptic QDs, with potential
technological applications to solid-state quantum computing.
(II) Particle localization at the vertices of concentric
polygonal rings and formation of rotating (and other less
symmetric) Wigner molecules in quantum dots and ultracold
rotating bosonic clouds [6].
(III) At high magnetic field (electrons) or rapid rotation
(neutral bosons), the method yields analytic trial wave
functions in the lowest Landau level [7], which are an
alternative to the fractional-quantum-Hall-effect (FQHE)
composite-fermion and Jastrow-Laughlin approaches.
(3) The physics of planar graphene nanorings with armchair
edge terminations shows analo- gies with the physics
described by the RQFT Jackiw-Rebbi model and the related
Su-Schrieffer- Heeger model of polyacetylene [4]. This part
of the talk will describe the emergence of exotic states and
properties, like solitons, charge fractionization, and
nontrivial topological insulators, in these graphene
nanosystems.
[1] C. Yannouleas, R.A. Broglia, M. Brack, and P.F.
Bortignon, Phys. Rev. Lett. 63, 255 (1989); [2] C.
Yannouleas, U. Landman, and R.N. Barnett, in Metal Clusters,
edited by
W. Ekardt (John-Wiley, New York, 1999) Ch. 4, p. 145; [3] C.
Yannouleas and U. Landman, Rep. Prog. Phys. 70, 2067 (2007),
and references therein; [4] I. Romanovsky, C. Yannouleas,
and U. Landman, Phys. Rev. B 87, 165431 (2013); Phys. Rev. B
89, 035432 (2014). [5] C. Yannouleas and U. Landman, Phys.
Rev. B 48, 8376 (1993); Ch. 7 in ”Recent Advances in
Orbital-Free Density Functional Theory,” Y.A. Wang and T.A.
Wesolowski Eds. (Word Scientific, Singapore, 2013) p. 203
(arXiv:1004.3536); [6] C. Yannouleas and U. Landman, Phys.
Rev. Lett. 82, 5325 (1999); I. Romanovsky, C. Yannouleas,
and U. Landman, Phys. Rev. Lett. 97, 090401 (2006). [7] C.
Yannouleas and U. Landman, Phys. Rev. A 81, 023609 (2010);
Phys. Rev. B 84, 165327 (2011).
