Physics Letters A 376 (2012) 1201–1206
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Physics Letters A
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Current-density functional study of the Neon atom in a strong ultrashort magnetic
field
Vikas
∗
Quantum Chemistry Group, Department of Chemistry & Centre of Advanced Studies in Chemistry, Panjab University, Chandigrah-160014, India
article info abstract
Article history:
Received 15 September 2011
Received in revised form 15 February 2012
Accepted 15 February 2012
Available online 20 February 2012
Communicated by C.R. Doering
Keywords:
TD-DFT
Strong magnetic field
Current-density functional theory
Ne atom
Exchange–correlation
Quantum fluid dynamics
A Ne atom exposed to a strong ultrashort magnetic field of the order of 10
9
G that lasts for a few
femtoseconds is investigated through a current-density functional theory (CDFT) based approach employ-
ing a vector exchange–correlation potential that depends on the electronic charge-density as well as on
the current-density of the atom. The CDFT based approach yields time-dependent electronic charge- and
current-density, along with the exchange–correlation potential and energy, significantly different from
that obtained using a current-density independent approach, in particular, at the field-strengths
>
10
9
G.
©
2012 Elsevier B.V. All rights reserved.
The magnetic white-dwarfs and surface of the neutron stars can
have strong magnetic field with the field-strength of the order of
10
9
G and more [1]. What happens to the electronic structure
of an atom when exposed to such a strong magnetic field? At
the magnetic field-strength of 2
.
3505
×
10
9
G (1 a.u. of magnetic
field), the electron cyclotron energy, for example in the hydro-
gen atom ground state, becomes equal to the Coulombic binding
energy. In the general case of a many-electron atom, this critical
field is 2
.
3505
×
10
9
· (
Z
eff
/
n
)
2
G where Z
eff
is the effective charge
and n is the main quantum number. At this critical field-strength,
spherical symmetric Coulombic forces compete with the cylindri-
cal symmetric Lorentz (magnetic) forces, with the latter dominat-
ing in the high-field regime of magnetic field-strengths (
>
1a.u.).
This competition causes a complete reconstruction of the electronic
structure of the exposed atom. For the electronic structure calcu-
lations of an atom in such strong magnetic fields, nonperturbative
approaches are indispensable (see Ref. [2] and references therein).
For a many-electron system, approaches based on the density-
functional theory (DFT) [3], and the time-dependent (TD)-DFT [4]
are computationally more affordable. However, all these studies in
the literature, we are aware of, are carried out for atomic sys-
tems exposed to the strong time-independent (TI) static magnetic
fields. In a recent study on the hydrogen atom in a strong TD mag-
netic field, the potential use of an ultrashort strong magnetic field
*
Tel.: +91 172 2534408; fax: +91 172 2544078.
E-mail addresses: qlabspu@pu.ac.in, qlabspu@yahoo.com.
for the attosecond spectroscopy has been explored [5].Moreover,
ultrafast magnetic pulses are becoming important for the develop-
ment of quantum computing [6] since ultrafast spin control can
be achieved using strong magnetic field of the ultrashort terahertz
pulses [7]. On the laboratory scale, a magnetic field of the order of
10
8
G over a femtoseconds (fs) time-scale can be produced during
interaction of a plasma with an ultra-intense laser of intensity of
the order of 10
18
Wcm
−
2
[8].
Recently, we have performed numerical computations on the
He atom [9,10] exposed to a strong TD magnetic field. These in-
vestigations, which are based on a quantum fluid dynamics (QFD)
and TD-DFT based approach [11–13], revealed not only prominent
similarities with the TI studies but also several other interesting
features in the dynamics of the studied system that could not
be predictable from the TI investigations involving static magnetic
fields. The correlated methods such as TD-DFT being computation-
ally economical are more suitable for study of atoms in a strong TD
magnetic field. However, the various TD-DFT based studies employ
only scalar exchange–correlation (XC) potential and XC energy den-
sity functional that depend only on the electronic charge-density.
On the contrary, in the presence of even a weak magnetic field,
strong currents can build up in the exposed system. This makes
dependence of the density-functional on the current-density in-
dispensable. This can be realized, within the DFT, through the
current-density functional theory (CDFT) [14,15]. The CDFT incor-
porates current-dependence through a vector XC potential and XC
energy density functional that depend not only on the electronic
charge-density but also on the current-density of the exposed
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©
2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.physleta.2012.02.033