Download Dielectric Function Approach to Room

Dielectric Function Approach
pp
to Room
Room-Temperature
Temperature
p
Superconductivity
p
y in Nanomaterials
A Gulian1, G
A.
G. Melkonyan2, M
M. Gulian3 C.
C Reilly4, S
S. Kasthurirengan4
1Chapman
University
University, Institute for Quantum Studies
Studies, Burtonsville
Burtonsville, MD 20866
20866, USA
3Brown University,
University Department of Mathematics,
Mathematics Providence,
Providence RI 02912,USA
02912 USA
2GMLab,
GMLab
873 Rue Jean-Noel,
Jean Noel Quebec
Quebec, G1X 2N3,
2N3 Canada
4Chapman University,
University Institute for Quantum Studies,
Studies Orange
Orange, CA 92866,
92866 USA
Introduction
Ab-Initio Calculations of (q,)
(q )
Our task is to apply the predictive power of theory of superconductivity
formulated in terms of the dielectric function (q,),
(q ) to nanostructures
nanostructures, such as
the decorated nanotubes.
nanotubes Importance of the dielectric function (q,)
(q ) became
very clear after the BCS approach (see,
(see e.g.,
e g Ref
Ref. [1]).
[1]) Kirzhnitz [2] explored the
admissible negative sign of (q,
(q =0)
0) in 1976.
1976 Dolgov and Maksimov [3]
demonstrated in 1979 that negative sign (q,
(q =0)<0
0)<0 really takes place in
superconductors such as Sn,
superconductors,
Sn Al
Al, but not in non-superconducting
non superconducting K.
K Using this
approach it was obtained recently that using metamaterial nanoengineering
triples the superconducting critical temperature of bulk aluminum [4].
[4]
For dielectric function (q,),
(q ) our calculations make use of the Density
Functional Theory (DFT) code ABINIT [5] and the add
add-on
on Time Dependent
Density Functional Theory (TDDFT) code DP [6].
[6] ABINIT was used to compute
the electronic density and band structure.
structure The computed data were then fed
into DP to calculate the dielectric function.
function Graphical interface of QuantumWise
commercial software was used for acceleration of relaxation studies.
studies
We obtained data on ab
ab-initio
initio calculations of (q,)
(q ) for GaAs,
GaAs Si
Si, Ge,
Ge Al
Al,
as well as for Ti
Ti-decorated
decorated nanotubes and the ropes of carbon nanotubes.
nanotubes
Negative sign of dielectric function and its possible cause of very high
high-T
Tc
superconductivity is under exploration in nanomaterials [7].
[7]
First p
principle
p calculations for Aluminum
-1
1
 (q
(q,=0)
=0))
No negativity
g
y of Re
in the frozen lattice model.
model
Concl
Conclusion:
Co
c ussion
o pphonons
o o s aaree important
po ta t for
o SC in this
t s material!
ate a
However, Ti-decorated
However,
Ti decorated nanotube delivers the desired tendency:
y
Predictive Power of Theoryy
BCS, 1957:
BCS,
Tc~Dexp ((-1/
1/)
Bogolyubov
g y
et al.,
al , 1958;; Eliashberg,
Eliashberg
g, 1960;; MacMillan,
MacMillan, 1968:
Tc~wDexp{1.04[(1+
exp{1
p{ 04[(1+
[( )]
)]/[[-*(1+0
((1+0.62
62)]}
Little, Ginzburg,
Little,
Ginzburg
g, 1964:
P l electronic
Purely
l t i mechanism!
h i !
Cohen, Anderson,
Cohen,
Anderson, 1972:
Tc>300K
V (q
( q,  ) 
4e
2
 ( q,  ) q
2
M
Moreover
Moreover,
for
f the
th ropes off CNTs:
CNT (q
( 0,)<1:
)<1:
) 1
Tc<10K
I
Importance
t
off (q,)
( )
Kirzhnitz, 1976: (q,
Kirzhnitz
(q =0)<0
is admissible!
D l
Dolgov,
M i
Maximov
1979
1979:
(q,
(q =0) is negative!!


dq
4e
2
 ( q ,   0) q
2
  
Known (q,
(q ) means the dynamics of the system is determined:
V (q,  )  V(Coulomb )  V( el  ph ) 
2
4e
2
 ( q,  ) q
2
2
q
2
1
q
 2
[
1

]
2
2
 (q,  ) q  kTF
  q
Historic
suggestions
gg
byy Little and
others
Nanostructures
calculable ab-initio
ab initio
andd achievable
hi bl
experimentally
i
ll
1st International Workshopp SUPERHYDRIDES: Towards Room Temperature
p
Superconductivity:
p
y Hydrides
y
and More
TEMPLATE DESIGN © 2008
www.PosterPresentations.com
N ti it off (q
Negativity
( 0,)
)) means we can expectt SC!
Still requires
q
more work which is ongoing…
ongoing
g g
A k
Acknowledgements
l d
t
We are grateful
g
to V.
V Olevano and O.
O Dolgov
g for useful discussions.
discussions
Thi workk iis supported
This
t d in
i partt by
b the
th ONR grantt N00014
N00014-15-1-2095.
15 1 2095.
2095
R f
References
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Zh Eksp.
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