Vortex dynamics in artificially fabricated superconducting networks

Applied Science

Transition from Strong to Weak Electronic Coupling in a Single-Molecule Junction

We have investigated charge transport in single-molecule junctions using gold nanoelectrodes at room and cryogenic (10 K) temperatures. A statistical analysis of the low-bias conductance, measured during the stretching of the molecular junctions, shows that the most probable single-molecule conductance is insensitive to the temperature as expected for off-resonant coherent transport. Low-temperature current-voltage measurements show that these junction conformations have a smooth tunnelinglike shape. While separating the electrodes further we find that, in about one-fourth of the cases, the junction switches in an abrupt way to a configuration with I-V characteristics exhibiting a gap around zero bias and resonances at finite bias. The analysis of the I-V shape and of the conductance distance dependence suggests a stretching-induced transition from the strong to the weak electronic coupling regime. The transition involves a large renormalization of the injection barrier and of the electronic coupling between the molecule and the electrodes.QN/van der Zant La

Single-molecule quantum-transport phenomena in break junctions

Single-molecule junctions — devices in which a single molecule is electrically connected by two electrodes — enable the study of a broad range of quantum-transport phenomena even at room temperature. These quantum features are related to molecular orbital and spin degrees of freedom and are characterized by various energy scales that can be chemically and physically tuned: level spacings, charging energies, tunnel couplings, exchange energies, vibrational energies and Kondo correlation energies. The competition between these different energy scales leads to a rich variety of processes, which researchers are now starting to be able to control and tune experimentally. In this Technical Review, we present the status of the molecular electronics field from this quantum-transport perspective with a focus on recent experimental results obtained using break-junction devices, including scanning probe and mechanically controlled break junctions, as well as electromigrated gold and graphene break junctions.Accepted Author ManuscriptQN/van der Zant LabQN/Thijssen Grou

Probing the local environment of a single OPE3 molecule using inelastic tunneling electron spectroscopy

We study single-molecule oligo(phenylene ethynylene)dithiol junctions by means of inelastic electron tunneling spectroscopy (IETS). The molecule is contacted with gold nano-electrodes formed with the mechanically controllable break junction technique. We record the IETS spectrum of the molecule from direct current measurements, both as a function of time and electrode separation. We find that for fixed electrode separation the molecule switches between various configurations, which are characterized by different IETS spectra. Similar variations in the IETS signal are observed during atomic rearrangements upon stretching of the molecular junction. Using quantum chemistry calculations, we identity some of the vibrational modes which constitute a chemical fingerprint of the molecule. In addition, changes can be attributed to rearrangements of the local molecular environment, in particular at the molecule–electrode interface. This study shows the importance of taking into account the interaction with the electrodes when describing inelastic contributions to transport through single-molecule junctions.QN/Quantum NanoscienceApplied Science

Efros-Shklovskii variable range hopping and nonlinear transport in 1T/1T′-MoS2

We have studied temperature- and electric-field-dependent carrier transport in single flakes of MoS2 treated with n-butyllithium. The temperature dependence of the four-terminal resistance follows the Efros-Shklovskii variable range hopping conduction mechanism. From measurements in the Ohmic and non-Ohmic regime, we estimate the localization length and the average hopping length of the carriers, as well as the effective dielectric constant. Furthermore, a comparison between two- and four-probe measurements yields a contact resistance that increases significantly with decreasing temperature.QN/Steele LabQN/van der Zant La

Thermoelectricity in single-molecule devices

As the miniaturization of electronics continuously progresses, harvesting and generating thermoelectric energy with high efficiency become a key concept to integrate. Theoretical studies suggest that single-molecule devices are ideal candidates for thermoelectric devices with unprecedentedly high efficiencies. Such advantage is achieved by molecular designs with ideal energy alignment, optimized tunnel coupling or strong quantum interference features, etc. In our single-molecule thermoelectric devices, we have demonstrated the possibility to extract important thermoelectric functions such as Seebeck coefficient and the power factor. In addition, we can obtain crucial physical parameters in single-molecule devices such as the entropy changes, excited states or the universality of the Kondo effect via the thermoelectric study. We expect, as our works have shown, thermoelectric studies in single-molecule devices will bring us more useful innovative devices and more fundamental understanding of nanoscale systems.QN/van der Zant La

Gate effect in charge-density wave nanowires

We have investigated transport characteristics of charge-density wave nanowires with a few hundred parallel chains. At temperatures below50K, these samples show power-law behavior in temperature and voltage, characteristic for one-dimensional transport. In this regime, gate dependent transport has been observed.kavli institute of nanoscienceApplied Science

Double quantum dots in suspended carbon nanotubes

Applied Science