Mixed-valence molecules provide an implementation for a high-speed, energy-efficient paradigm for classical computing known as quantum-dot cellular automata (QCA). The primitive device in QCA is a cell, a structure with multiple quantum dots and a few mobile charges. A single mixed-valence molecule can function as a cell, with redox centers providing quantum dots. The charge configuration of a molecule encodes binary information, and device switching occurs via intramolecular electron transfer between dots. Arrays of molecular cells adsorbed onto a substrate form QCA logic. Individual cells in the array are coupled locally via the electrostatic electric field. This device networking enables general-purpose computing. Here, a quantum model of a two-dot molecule is built in which the two-state electronic system is coupled to the dominant nuclear vibrational mode via a reorganization energy. This model is used to explore the effects of the electronic inter-dot tunneling (coupling) matrix element and the reorganization energy on device switching. A semi-classical reduction of the model also is made to investigate the competition between field-driven device switching and the electron-vibrational self-trapping. A strong electron-vibrational coupling (high reorganization energy) gives rise to self-trapping, which inhibits the molecule's ability to switch. Nonetheless, there remains an expansive area in the tunneling-reorganization phase space where molecules can support adequate tunneling. Thus, the relationship between the tunneling matrix element and the reorganization energy affords significant leeway in the design of molecules viable for QCA applications.

1.
C.
Lent
,
P.
Tougaw
,
W.
Porod
, and
G.
Bernstein
, “
Quantum cellular automata
,”
Nanotechnology
4
,
49
(
1993
).
2.
C. S.
Lent
,
P. D.
Tougaw
, and
W.
Porod
, “
Bistable saturation in coupled quantum dots for quantum cellular automata
,”
Appl. Phys. Lett.
62
,
714
716
(
1993
).
3.
P.
Tougaw
and
C.
Lent
, “
Logical devices implemented using quantum cellular automata
,”
J. Appl. Phys.
75
,
1818
1825
(
1994
).
4.
C. S.
Lent
, “
Molecular electronics - bypassing the transistor paradigm
,”
Science
288
,
1597
(
2000
).
5.
M.
Niemier
and
P.
Kogge
, “
Logic in wire: Using quantum dots to implement a microprocessor
,” in
Proceedings - Great Lakes Symposium on VLSI 9th Great Lakes Symposium on VLSI
(GLSVLSI 99), YPSILANTI, MI
,
04–06 March 1999
, edited by
R.
Lomax
and
P.
Mazumder
(
1999
), pp.
118
121
.
6.
M.
Niemier
and
P. M.
Kogge
, “
Problems in designing with QCAs: Layout = timing
,”
Int. J. Circuit Theory Appl.
29
,
49
62
(
2001
).
7.
J.
Christie
,
R.
Forrest
,
S.
Corcelli
,
N.
Wasio
,
R.
Quardokus
,
R.
Brown
,
S.
Kandel
,
Y.
Lu
,
C.
Lent
, and
K.
Henderson
, “
Synthesis of a neutral mixed-valence diferrocenyl carborane for molecular quantum-dot cellular automata applications
,”
Angew. Chem.
127
,
15668
15671
(
2015
).
8.
R. C.
Quardokus
,
N. A.
Wasio
,
R. P.
Forrest
,
C. S.
Lent
,
S. A.
Corcelli
,
J. A.
Christie
,
K. W.
Henderson
, and
S. A.
Kandel
, “
Adsorption of diferrocenylacetylene on au(111) adsorption of diferrocenylacetylene on au(111) studied by scanning tunneling microscopy
,”
Phys. Chem. Chem. Phys.
15
,
6973
6981
(
2013
).
9.
Y.
Lu
and
C.
Lent
, “
Field-induced electron localization: Molecular quantum-dot cellular automata and the relevance of robin–day classification
,”
Chem. Phys. Lett.
633
,
52
57
(
2015
).
10.
T.
Holstein
, “
Studies of polaron motion Part I. the molecular-crystal model
,”
Ann. Phys. - N. Y.
8
,
325
342
(
1959
).
11.
J.
Timler
and
C. S.
Lent
, “
Power gain and dissipation in quantum-dot cellular automata
,”
J. Appl. Phys.
91
,
823
831
(
2002
).
12.
C.
Lent
and
P.
Tougaw
, “
A device architecture for computing with quantum dots
,”
Proc. IEEE
85
,
541
557
(
1997
).
13.
E.
Blair
,
S.
Corcelli
, and
C.
Lent
, “
Electric-field-driven electron-transfer in mixed-valence molecules
,”
J. Chem. Phys.
145
,
014307
(
2016
).
14.
E. P.
Blair
and
C. S.
Lent
, “
Environmental decoherence stabilizes quantum-dot cellular automata
,”
J. Appl. Phys.
113
,
124302
(
2013
).
15.
J. S.
Ramsey
and
E. P.
Blair
, “
Operator-sum models of quantum decoherence in molecular quantum-dot cellular automata
,”
J. Appl. Phys.
122
,
084304
(
2017
).
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