08:45  09:00

Frank Jülicher
(Director MPIPKS)
& Scientific Organizers
Opening of the Workshop

09:00  09:40

Herre van der Zant
(Delft University of Technology)
Destructive quantum interference in singlemolecule junctions
Quantum interference effects are at the core of modern physics. Especially fascinating is the fact that interference of electron waves is directly observable through the conductance of a phasecoherent conductor. In general, constructive interference leads to enhanced conductance values, whereas destructive interference results in suppression. We have studied these interference effects in a series of molecules contacted to metallic electrodes: (i) the effect of quantum interference through a single para and meta coupled benzene ring was shown using a mechanically controlled breakjunction [1], (ii) in a anthraquinone transistor where charging the molecule led to a tenfold increase of the offresonant conductance indicating electrical control over interference effects [2], (iii) a donoracceptor pair coupled to a OPE3 backbone was used to switch the conducting pathway from linearly to crossconjugated with a corresponding tenfold conductance decrease [3] and (iv)finally, pistacked dimers were employed to mechanically control quantum interference effects [4]. In the latter experiment, the conductance through the molecule pair changes by two orders of magnitude while changing the electrode distance by 50 picometer.
Research supported by the national funding agencies NWO/OCW/FOM and by an ERC Advanced grant (Mols@Mols).
References:
[1] C.R. Arroyo et al., Angewandte Chemie Int. Ed. 52 (2013) 3152–3155C.R. Arroyo et al., Nanoscale Research Letters 8 (2013) 234.
[2] M. Koole et al., Nano Letters 15 (2015) 55695573.
[3] H. Lissau et al., Nature Communications 6 (2015) 10233.
[4] R. Frisenda et al., Nature Chemistry 8 (2016) 1099–1104.

09:40  10:05

Tomás Novotný
(Charles University of Prague)
Graphtheoretical evaluation of the inelastic propensity rules for molecules with destructive quantum interference
We present a method based on graph theory for evaluation of the inelastic
propensity rules for molecules exhibiting complete destructive quantum
interference in their elastic transmission. The method uses an extended
adjacency matrix corresponding to the structural graph of the molecule
for calculating the Green function between the sites with attached
electrodes and consequently states the corresponding conditions
the electronvibration coupling matrix must meet for the observation
of an inelastic signal between the terminals. The method can
be fully automated and we provide a functional website running a code
using Wolfram Mathematica, which returns a graphical depiction of
destructive quantum interference configurations together with the
associated inelastic propensity rules for a wide class of molecules.

10:05  10:45

Michael Thoss
(Friedrich Alexander University Erlangen Nürnberg)
Charge transport in molecular junctions: vibrational effects, interference and decoherence
Molecular junctions, i.e. single molecules bound to electrodes, are interesting systems to study nonequilibrium quantum transport at the nanoscale. An important transport mechanism in molecular junctions is electronicvibrational coupling. In this talk, various mechanisms and phenomena of vibrationally coupled electron transport are analyzed, including currentinduced vibrational excitation [1], nonadiabatic effects [2], and fluctuations [3]. Furthermore, quantum interference effects and their quenching due to vibrationally induced decoherence are discussed [1,4]. The studies employ a combination of generic as well as firstprinciples based models and different transport methods, including nonequilibrium Green's functions [1,2] and the hierarchical quantum master equation approach [5].
[1] R. Härtle, U. Peskin, M. Thoss, Phys. Status Solidi B 250, 2365 (2013).
[2] A. Erpenbeck, R. Härtle, M. Thoss, Phys. Rev. B 91, 195418 (2015).
[3] C. Schinabeck, R. Härtle, H. B. Weber, M. Thoss, Phys. Rev. B 90, 075409 (2014).
[4] R. Härtle, M. Butzin, O. RubioPons, M. Thoss, Phys. Rev. Lett. 107, 046802 (2011); Phys. Rev. B 87, 085422 (2013); S. Ballmann, R. Härtle, P.B. Coto, M. Mayor, M. Elbing, M. Bryce, M. Thoss, H.B. Weber, Phys. Rev. Lett. 109 , 056801 (2012),
[5] C. Schinabeck, A. Erpenbeck, R. Härtle, M. Thoss, Phys. Rev. B 94, 201407(R) (2016).

10:45  11:10

Coffee break

11:10  11:50

Andrew Sachrajda
(National Research Council of Canada)
LandauZenerStückelberg interferometry in quantum dots in the presence of phonons and non spin conserving tunneling

11:50  12:30

Gloria Platero
(Material Science Institute of Madrid)
Long range transport and dark states in driven quantum dot arrays
Superpositions of indirectly coupled states are possible in quantum mechanics even when the intermediate states are far apart in energy. This is achieved via higherorder transitions in which the energetically forbidden intermediate states are only virtually occupied. Interest in such longrange transitions has increased recently within the context of quantum information processing with the possibility of low dissipation transfer of quantum states or coherent manipulation of two distant qubits .The recently achieved control and tunability of triple quantum dots allow to investigate phenomena relying on quantum superpositions of distant states mediated by tunneling. Recent experiments in these devices show clear evidence of charge and spin electron exchange between the outermost dots[13].
We investigate longrange transport and quantum interferences in ac driven triple dots where transitions between distant and detuned dots are mediated by the exchange of photons[4]. We propose the phase difference between the two ac voltages as an external parameter, which can be easily tuned to manipulate the current characteristics. For gate voltages in phase opposition we find quantum destructive interferences among longrange and direct photonassisted transitions, analogous to the interferences in closedloop undriven triple dots. As the voltages oscillate in phase, interferences between multiple virtual paths give rise to dark states. Those totally cancel the current, and could be experimentally resolved.
1. M. Busl et al., Nature Nanotech. 8, 261 (2013).
2. F. Braakman et al., Nat. Nanotech.,8,432 (2013).
3. R. Sánchez, G. Granger, L. Gaudreau, A. Kam, M. PioroLadrière, S. A. Studenikin, P. Zawadzki, A. S. Sachrajda and G. Platero, PRL, 112, 176803 (2014).
4. F. GallegoMarcos, R. Sánchez and G. Platero, PRB, 93, 075424 (2016)

12:30  14:30

Lunch and discussions

14:30  15:10

Stefano Sanvito
(Trinity College Dublin)
The many ways for a current to interact with ionic motion
We explain how the electrical current flow in a molecular junction can modify the vibrational spectrum of the molecule by renormalizing its normal modes of oscillations. This is demonstrated with firstprinciples selfconsistent transport theory, where the currentinduced forces are evaluated from the expectation value of the ionic momentum operator. We explore here the case of H2 sandwiched between two Au electrodes and show that the current produces stiffening of the transverse translational and rotational modes and softening of the stretching modes along the current direction. Such behavior is understood in terms of charge redistribution, potential drop, and elasticity changes as a function of the current.

15:10  15:50

Latha Venkataraman
(Columbia University)
tba

15:50  16:15

Coffee break

16:15  16:55

Philippe Lafarge
(University Paris Diderot)
tba

16:55  17:20

Dmitry Ryndyk
(University of Bremen)
Dephasing and coherent to incoherent crossover

17:20  18:00

Robert Stadler
(Vienna University of Technology)
Destructive quantum interference in electron transport: A reconciliation of the molecular orbital and the atomic orbital perspective
Since the concepts for the implementation of data storage and logic gates used in conventional electronics cannot be simply downscaled to the level of single molecule devices, new architectural paradigms are needed, where quantum interference (QI) effects are likely to provide an useful starting point. In order to be able to use QI for design purposes in single molecule electronics, the relation between their occurrence and molecular structure has to be understood at such a level that simple guidelines for electrical engineering can be established. We made a big step towards this aim by developing a graphical scheme that allows for the prediction of the occurrence or absence of QI induced minima in the transmission function and the derivation of this method and the range of its applicability will form the first part of this presentation [1],[2],[3]. In the second part the scheme will be contrasted with a molecular orbital perspective on understanding and predicting QI effects, which was derived from the CoulsonRushbrooke pairing theorem in quantum chemistry [4].
[1] R. Stadler, S. Ami, M. Forshaw, and C. Joachim, Nanotechnology 15, S115S121 (2004).
[2] T. Markussen, R. Stadler, K. S. Thygesen, Nano Lett. 10, 42604265 (2010).
[3] R. Stadler, Nano Lett., 15, 7175–7176 (2015).
[4] X. Zhao, V. Geskin and R. Stadler, accepted for publication in a special issue on "Frontiers in Molecular Scale Electronics" of J. Chem. Phys. (2017); http://arxiv.org/abs/1612.02266

18:30  19:30

Dinner

19:30  21:30

Poster session
