Current rectification in molecular junctions produced by local potential fields

The transport properties of a octane-dithiol (ODT) molecule coupled to Au(001) leads are analyzed using density functional theory and non-equilibrium Green functions. It is shown that a symmetric molecule can turn into a diode under influence of a local electric field created by an external charged probe. The origin of the asymmetry of the current--voltage ($I-V$) dependence is traced back to the appearance of a probe induced quasi--local state in the pseudogap of the ODT molecule. The induced state affects electron transport, provided it is close to the Fermi level of the leads. An asymmetric placement of the charged probe along the alkane chain makes the induced quasi--local state in the energy gap very sensitive to the bias voltage and results in rectification of the current. The results based on DFT are supported by independent calculations using a simple one--particle model Hamiltonian.Comment: 7 pages, 6 figure

On determining defects identity in carbon nanotubes using charge probes

A metallic carbon nanotube with point-like defects under influence of a local potential due to a point charge probe is theoretically studied. A combination of density functional theory and the Landauer-Büttiker formalism is used to compute the electronic conductance in the zero-voltage limit. From a collection of the results obtained by varying the probe position around different defects the conductance maps are created. The analysis of the conductance maps allows us to formulate conditions under which several point-like defects (the Stone-Wales defect, a simple carbon vacancy, hydrogen-passivated vacancies) can be distinguished and identified in experiments with the help of scanning probe microscopy.This work has been supported by the National Science Centre under the contract DEC-2012/07/B/ST3/03412. We acknowledge that the results of this research have been achieved using the PRACE-3IP project (FP7 RI-312763) resource JUROPA based in Germany at Julich. We also thank the Spanish MICINN for the Grant No. FIS2012-34858 (V.M.G.S. and J.F.) and the Ramón y Cajal Fellowship No. RYC-2010-06053 (V.M.G.S.).Peer Reviewe

Effects of acceptor doping on a metalorganic switch: DFT: vs. model analysis

We propose a molecular switch based on copper dioxolene molecules with valence tautomeric properties. We study the system using density functional theory and a model Hamiltonian that can properly account for electronic correlations in these complex molecular systems. We compute the transport properties of the junction with a Cu-dioxolene unit sandwiched between gold electrodes and analyze its dependence on the valence tautomeric state of the molecule. We also study the effects of doping with ICl acceptor molecules on the magnetic and electronic features of the device. We find that in the absence of dopants, the Cu-dioxolene unit is weakly charged in a S = 1/2 spin state. However, the acceptors increase the charge state of the molecule and make possible a transition between the high-spin (S = 1) triplet and the low-spin (S = 0) singlet. The I-V dependence shows a manifestation of spin filtering and a voltage-induced multistable behavior that can have several applications in nanoscale electronic devices.We thank Bogdan Bułka for helpful advices. This work has been supported by the National Science Centre under the contract DEC-2012/07/B/ST3/03412. Our computations were performed at the Poznan's Supercomputing and Networking Center. V. M. G.-S. thanks the Spanish Ministerio de Economía, Industria y Competitividad for funding through the project FIS2015-63918-R.Peer Reviewe

Pamięć i materialne ślady zbrodni z czasów II wojny światowej w chojnickiej Dolinie Śmierci

Niniejszy artykuł dotyczy Doliny Śmierci – północnych obrzeży Chojnic, gdzie funkcjonariusze III Rzeszy dokonywali w czasie trwania II wojny światowej masowych mordów na polskiej ludności. W pracy zarysowano historię miejsca, omówiono też metodykę badawczą (wykorzystane metody i techniki archeologiczne, a także ich integrację ze źródłami historycznymi oraz żywą pamięcią), które pozwoliły na odkrycie i późniejszą ekshumację spalonych szczątków ofiar z drugiej połowy stycznia 1945 r.Projekt finansowany przez Narodowe Centrum Nauki na podstawie umowy nr UMO-2021/43/D/HS3/00033