Showing papers on "Conductance published in 2006"
TL;DR: Amine link groups are used to form single-molecule junctions with more reproducible current–voltage characteristics and it is found that the conductance for the series decreases with increasing twist angle, consistent with a cosine-squared relation predicted for transport through π-conjugated biphenyl systems.
Abstract: Since it was first suggested1 that a single molecule might function as an active electronic component, a number of techniques have been developed to measure the charge transport properties of single molecules2,3,4,5,6,7,8,9,10,11,12. Although scanning tunnelling microscopy observations under high vacuum conditions can allow stable measurements of electron transport, most measurements of a single molecule bonded in a metal–molecule–metal junction exhibit relatively large variations in conductance. As a result, even simple predictions about how molecules behave in such junctions have still not been rigorously tested. For instance, it is well known13,14 that the tunnelling current passing through a molecule depends on its conformation; but although some experiments have verified this effect15,16,17,18, a comprehensive mapping of how junction conductance changes with molecular conformation is not yet available. In the simple case of a biphenyl—a molecule with two phenyl rings linked by a single C–C bond—conductance is expected to change with the relative twist angle between the two rings, with the planar conformation having the highest conductance. Here we use amine link groups to form single-molecule junctions with more reproducible current–voltage characteristics19. This allows us to extract average conductance values from thousands of individual measurements on a series of seven biphenyl molecules with different ring substitutions that alter the twist angle of the molecules. We find that the conductance for the series decreases with increasing twist angle, consistent with a cosine-squared relation predicted for transport through π-conjugated biphenyl systems13.
1,266 citations
TL;DR: In this paper, the authors measured the conductance of amine-terminated molecules by breaking Au point contacts in a molecular solution at room temperature, and they found that the variability of the observed conductance for the diamine molecule−Au junctions is much less than the variability for diisonitrile− and dithiol−AU junctions.
Abstract: We measure the conductance of amine-terminated molecules by breaking Au point contacts in a molecular solution at room temperature. We find that the variability of the observed conductance for the diamine molecule−Au junctions is much less than the variability for diisonitrile− and dithiol−Au junctions. This narrow distribution enables unambiguous conductance measurements of single molecules. For an alkane diamine series with 2−8 carbon atoms in the hydrocarbon chain, our results show a systematic trend in the conductance from which we extract a tunneling decay constant of 0.91 ± 0.03 per methylene group. We hypothesize that the diamine link binds preferentially to undercoordinated Au atoms in the junction. This is supported by density functional theory-based calculations that show the amine binding to a gold adatom with sufficient angular flexibility for easy junction formation but well-defined electronic coupling of the N lone pair to the Au. Therefore, the amine linkage leads to well-defined conductanc...
753 citations
TL;DR: Insight into the binding strengths of these anchoring groups to gold electrodes is obtained by statistically analyzing the stretching length of molecular junctions.
Abstract: We studied the effect of anchoring groups on the conductance of single molecules using alkanes terminated with dithiol, diamine, and dicarboxylic-acid groups as a model system. We created a large number of molecular junctions mechanically and analyzed the statistical distributions of the conductance values of the molecular junctions. Multiple sets of conductance values were found in each case. The I−V characteristics, temperature independence, and exponential decay of the conductance with the molecular length all indicate tunneling as the conduction mechanism for these molecules. The prefactor of the exponential decay function, which reflects the contact resistance, is highly sensitive to the anchoring group, and the decay constant is weakly dependent on the anchoring group. These observations are attributed to different electronic couplings between the molecules and the electrodes and alignments of the molecular energy levels relative to the Fermi energy level of the electrodes introduced by different an...
690 citations
TL;DR: The conduction mechanism in alkanedithiols is due to electron tunneling or superexchange via the bonds along the molecules, and the two sets of conductance peaks are due to two different microscopic configurations of the molecule-electrode contacts.
Abstract: The conductance of single alkanedithiols covalently bound to gold electrodes has been studied by statistical analysis of repeatedly created molecular junctions. For each molecule, the conductance histogram reveals two sets of well-defined peaks, corresponding to two different conductance values. We have found that (1) both conductance values decrease exponentially with the molecular length with an identical decay constant, β ≈ 0.84 A-1, but with a factor of 5 difference in the prefactor of the exponential function. (2) The current−voltage curves of the two sets can be fit with the Simmons tunneling model. (3) Both conductance values are independent of temperature (between −5 and 60 °C) and the solvent. (4) Despite the difference in the conductance, the forces required to break the molecular junctions are the same, 1.5 nN. These observations lead us to believe that the conduction mechanism in alkanedithiols is due to electron tunneling or superexchange via the bonds along the molecules, and the two sets of...
497 citations
Journal Article•
327 citations
Journal Article•
TL;DR: In this paper, the thermal conductance of interfaces between Al and Cu was measured in the temperature range 78 T 298 K using time-domain thermoreflectance, which is an order-of-magnitude larger than the phonon-mediated thermal conductances of typical metal-dielectric interfaces.
Abstract: The thermal conductance of interfaces between Al and Cu is measured in the temperature range 78 T 298 K using time-domain thermoreflectance. The samples are prepared by magnetron sputter deposition of a 100 nm thick film of Al on top of layers of Cu on sapphire substrates. The chemical abruptness of the Al-Cu interface is systematically varied by ion-beam mixing using 1 MeV Kr ions. The thermal conductance of the as-deposited Al-Cu interface is 4 GW m−2 K−1 at room temperature, an order-of-magnitude larger than the phonon-mediated thermal conductance of typical metal-dielectric interfaces. The magnitude and the linear temperature dependence of the conductance are described well by a diffuse-mismatch model for electron transport at interfaces.
266 citations
TL;DR: In this paper, the authors investigated the temperature and frequency dependence of conductivity of polymer matrix-metal particles composites and provided evidence for the charge carriers transport mechanism via the occurred agreement of experimental results with the employed hopping models (variable range hopping model and random free energy barrier model).
Abstract: Charge transport properties, such as the temperature dependent dc conductivity and the frequency dependent conductance, of polymer matrix–metal particles composites, are investigated in the present study. Dc and ac conductivity is examined with varying parameters the filler content, temperature and the frequency in the case of ac field. The examined systems, though they are characterized as dielectrics, exhibit considerable conductivity, which alters by several orders of magnitude with temperature and frequency. The temperature and frequency dependence of conductivity gives evidence for the charge carriers transport mechanism via the occurred agreement of experimental results with the employed hopping models (variable range hopping model and random free-energy barrier model).
260 citations
TL;DR: This paper addresses the mechanism of the amyloid hypothesis of Alzheimer's toxicity, and finds that only oligomers increase the conductance of lipid bilayers and patch-clamped mammalian cells, producing almost identical current–voltage curves in both preparations.
Abstract: The amyloid hypothesis of Alzheimer's toxicity has undergone a resurgence with increasing evidence that it is not amyloid fibrils but a smaller oligomeric species that produces the deleterious results. In this paper we address the mechanism of this toxicity. Only oligomers increase the conductance of lipid bilayers and patch-clamped mammalian cells, producing almost identical current-voltage curves in both preparations. Oligomers increase the conductance of the bare bilayer, the cation conductance induced by nonactin, and the anion conductance induced by tetraphenyl borate. Negative charge reduces the sensitivity of the membrane to amyloid, but cholesterol has little effect. In contrast, the area compressibility of the lipid has a very large effect. Membranes with a large area compressibility modulus are almost insensitive to amyloid oligomers, but membranes formed from soft, highly compressible lipids are highly susceptible to amyloid oligomer-induced conductance changes. Furthermore, membranes formed using the solvent decane (instead of squalane) are completely insensitive to the presence of oligomers. One simple explanation for these effects on bilayer conductance is that amyloid oligomers increase the area per molecule of the membrane-forming lipids, thus thinning the membrane, lowering the dielectric barrier, and increasing the conductance of any mechanism sensitive to the dielectric barrier.
224 citations
TL;DR: Robust differences are found between monovalent and divalent additions, while divalent addends create impurity states far away from the Fermi level.
Abstract: We investigated the conducting properties of functionalized single wall nanotubes (SWNTs) with a finite addend concentration. Robust differences are found between monovalent and divalent additions. For the former a small number of addends can significantly disrupt the ballistic conductance of nanotubes near the Fermi level. As the concentration increases the conductance decreases rapidly and approaches zero at addend to C ratio around 25%. In contrast, divalent functionalizations have weak effects, and the nanotube quantum conductance remains above 50% of that of a perfect tube even for an addend concentration as large as 25%. These differences can be attributed to the formation of impurity states near the Fermi level for monovalent additions, while divalent addends create impurity states far away from the Fermi level.
204 citations
TL;DR: The method roots in the physics of tunneling and is tested on octanedithiol using mechanically controllable break junctions and can be deduced without the need for data selection.
Abstract: We propose an objective and robust method to extract the electrical conductance of single molecules connected to metal electrodes from a set of measured conductance data. Our method roots in the physics of tunneling and is tested on octanedithiol using mechanically controllable break junctions. The single molecule conductance values can be deduced without the need for data selection.
199 citations
TL;DR: The geometrical junction to junction variations dominate the conductance measurements, and Histograms constructed from all conductance traces do not show clear peaks either at room or low temperatures.
Abstract: The conductance of molecular junctions, formed by breaking gold point contacts dressed with various thiol functionalized organic molecules, is measured at 293 K and at 30 K. In the presence of molecules, individual conductance traces measured as a function of increasing gold electrode displacement show clear steps below the quantum conductance steps of the gold contact. These steps are distributed over a wide range of molecule-dependent conductance values. Histograms constructed from all conductance traces therefore do not show clear peaks either at room or low temperatures. Filtering of the data sets by an objective automated procedure only marginally improves the visibility of such features. We conclude that the geometrical junction to junction variations dominate the conductance measurements.
TL;DR: It is inferred that nanometer-sized gaseous bubbles (nanobubbles) are the dominant noise source in solid-state nanopores and an unexpected double-peak ionic conductance profile is measured.
Abstract: From conductance and noise studies, we infer that nanometer-sized gaseous bubbles (nanobubbles) are the dominant noise source in solid-state nanopores. We study the ionic conductance through solid-state nanopores as they are moved through the focus of an infrared laser beam. The resulting conductance profiles show strong variations in both the magnitude of the conductance and in the low-frequency noise when a single nanopore is measured multiple times. Differences up to 5 orders of magnitude are found in the current power spectral density. In addition, we measure an unexpected double-peak ionic conductance profile. A simple model of a cylindrical nanopore that contains a nanobubble explains the measured profile and accounts for the observed variations in the magnitude of the conductance.
TL;DR: In this paper, the authors reported on a pronounced conductance peak observed at finite bias voltage in a carbon-nanotube quantum dot in the spin-singlet ground state, and they explained this finite-bias conductance anomaly by a non-equilibrium Kondo effect involving excitations into a spin-triplet state.
Abstract: The Kondo effect is a many-body phenomenon arising due to conduction electrons scattering off a localized spin1. Coherent spin-flip scattering off such a quantum impurity correlates the conduction electrons, and at low temperature this leads to a zero-bias conductance anomaly2,3. This has become a common signature in bias spectroscopy of single-electron transistors, observed in GaAs quantum dots4,5,6,7,8,9 as well as in various single-molecule transistors10,11,12,13,14,15. Although the zero-bias Kondo effect is well established, the extent to which Kondo correlations persist in non-equilibrium situations where inelastic processes induce decoherence remains uncertain. Here we report on a pronounced conductance peak observed at finite bias voltage in a carbon-nanotube quantum dot in the spin-singlet ground state. We explain this finite-bias conductance anomaly by a non-equilibrium Kondo effect involving excitations into a spin-triplet state. Excellent agreement between calculated and measured nonlinear conductance is obtained, thus strongly supporting the correlated nature of this non-equilibrium resonance.
TL;DR: A class of covalent functionalizations that preserve or control the conductance of single-walled metallic carbon nanotubes is identified, where certain addends exhibit a bistable state, where the opening or closing of the sidewall bond, accompanied by a switch in the Conductance, could be directed with chemical, optical, or thermal means.
Abstract: We identify a class of covalent functionalizations that preserve or control the conductance of single-walled metallic carbon nanotubes. [2+1] cycloadditions can induce bond cleaving between adjacent sidewall carbons, recovering in the process the sp;{2} hybridization and the ideal conductance of the pristine tubes. This is radically at variance with the damage permanently induced by other common ligands, where a single covalent bond is formed with a sidewall carbon. Chirality, curvature, and chemistry determine bond cleaving, and in turn the electrical transport properties of a functionalized tube. A well-defined range of diameters can be found for which certain addends exhibit a bistable state, where the opening or closing of the sidewall bond, accompanied by a switch in the conductance, could be directed with chemical, optical, or thermal means.
TL;DR: The electrical conductance of a series of thiol-terminated alkanes was measured using a modified scanning tunneling microscope break junction technique and a new method called the last-step analysis (LSA) was introduced here to clarify the contribution of these effects.
Abstract: The electrical conductance of a series of thiol-terminated alkanes, (1,6-hexanedithiol (HDT), 1,8-octanedithiol (ODT), and 1,10-decanedithol (DDT)) was measured using a modified scanning tunneling ...
TL;DR: Experimental evidence for atomic chain formation during stretching of atomic-sized contacts for gold and silver, that is strongly enhanced due to oxygen incorporation, is reported.
Abstract: We report experimental evidence for atomic chain formation during stretching of atomic-sized contacts for gold and silver, that is strongly enhanced due to oxygen incorporation. While gold has been known for its tendency to form atomic chains, for silver this is only observed in the presence of oxygen. With oxygen the silver chains are as long as those for gold, but the conductance drops with chain length to about 0.1 conductance quantum. A relation is suggested with previous work on surface reconstructions for silver (110) surfaces after chemisorption of oxygen.
TL;DR: Findings demonstrate that charge transport through single organic molecules at ambient temperatures is a subtle and highly dynamic process that cannot be described by analysing only one molecular conformation corresponding to the lowest energy geometry of the molecule.
Abstract: The temperature dependence of the single molecule conductance (SMC) of α,ω-alkanedithiols has been investigated using a scanning tunnelling microscopy (STM) method. This is based on trapping molecules between a gold STM tip and a gold substrate and measuring directly the current across the molecule under different applied potentials. A pronounced temperature dependence of the conductance, which scales logarithmically with T−1, is observed in the temperature range between 293 and 353 K. It is proposed that the origin of this dependence is the change in distribution between molecular conformers rather than changes in either the conduction mechanism or the electronic structure of the molecule. For alkanedithiols the time averaged conformer distribution shifts to less elongated conformers at higher temperatures thus giving rise to higher conductance across the molecular bridges. This is analysed by first calculating energy differences between different conformers and then calculating their partition distribution. A simple tunnelling model is then used to calculate the temperature dependent conductance based on the conformer distribution. These findings demonstrate that charge transport through single organic molecules at ambient temperatures is a subtle and highly dynamic process that cannot be described by analysing only one molecular conformation corresponding to the lowest energy geometry of the molecule.
TL;DR: Electrochemical transport in bipyridyl-dinitro oligophenylene-ethynelene dithiol molecules both in an inert environment and in aqueous electrolyte under potential control showed a linear dependence of the bias for switching on the electrochemical potential.
Abstract: We have studied electron transport in bipyridyl-dinitro oligophenylene-ethynelene dithiol (BPDN) molecules both in an inert environment and in aqueous electrolyte under potential control, using scanning tunneling microscopy. Current-voltage (IV) data obtained in an inert environment were similar to previously reported results showing conductance switching near 1.6 V. Similar measurements taken in electrolyte under potential control showed a linear dependence of the bias for switching on the electrochemical potential. Extrapolation of the potentials to zero switching bias coincided with the potentials of redox processes on these molecules. Thus switching is caused by a change in the oxidation state of the molecules.
TL;DR: The use of a logarithmic current-to-voltage converter is reported to examine a wide range of currents in an STM break junction study of octanedithiol, clearly showing both the gold-quantum wire regime and the single molecule conductance regime.
Abstract: Single-molecule conductance measurements made under potential control provide a critical link between chemical and molecular electronic data. These measurements are made possible by the STM break-junction method introduced recently, but questions remain about its reliability. Here we report the use of a logarithmic current-to-voltage converter to examine a wide range of currents in an STM break junction study of octanedithiol, clearly showing both the gold-quantum wire regime and the single molecule conductance regime. We find two sets of molecular currents that we tentatively ascribe to different bonding geometries of the molecules in the break junction.
TL;DR: In this article, the influence of doping on the conductance of surface-passivated silicon nanowires is investigated. And the authors show that impurities located in the core of the wire induce a strong resonant backscattering at the impurity bound state energies.
Abstract: We perform ab initio calculations within the Landauer formalism to study the influence of doping on the conductance of surface-passivated silicon nanowires. It is shown that impurities located in the core of the wire induce a strong resonant backscattering at the impurity bound state energies. Surface dangling bond defects have hardly any direct effect on conductance, but they strongly trap both p- and n-type impurities, as evidenced in the case of H-passivated wires and Si/SiO2 interfaces. Upon surface trapping, impurities become transparent to transport, as they are electrically inactive and do not induce any resonant backscattering.
TL;DR: In this article, a multilevel conductance switching in poly[2methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) films is demonstrated.
Abstract: Multilevel conductance switching in poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) films is demonstrated. A thin-film structure, ITO-coated glass/MEH-PPV/Al, has shown the ability to store a continuum of conductance states. These states are nonvolatile and can be switched reproducibly by applying appropriate programing biases above a certain threshold voltage. The electrical conductivity of the highest and lowest states can differ by five orders of magnitude. Furthermore, these devices exhibit good cyclic switching characteristics and retention times of several weeks.
TL;DR: In this paper, the authors extended the analysis of Au conductance histograms to different types of metals, namely, Ag, Pt and ferromagnetic Ni, and concluded that the differences in the histograms of these metals are due to i the very different electronic structures, which means different atomic orbitals contributing to the transport and ii the different mechanical properties, which in a case such as Pt lead to the formation of monoatomic chains.
Abstract: Conductance histograms are a valuable tool to study the intrinsic conduction properties of metallic atomicsized contacts. These histograms show a peak structure, which is characteristic of the type of metal under investigation. Despite the enormous progress in the understanding of the electronic transport in metallic nanowires, the origin of this peak structure is still a basic open problem. In the present work we tackle this issue, extending our theoretical analysis of Au conductance histograms Dreher et al., Phys. Rev. B 72, 075435 2005 to different types of metals, namely, Ag, Pt and ferromagnetic Ni. We combine classical molecular dynamics simulations of the breaking of nanocontacts with conductance calculations based on a tight-binding model. This combination gives us access to crucial information such as contact geometries, strain forces, minimum cross-sections, the conductance, transmissions of the individual conduction channels, and, in the case of Ni, the spin polarization of the current. We shall also briefly discuss investigations of Al atomic-sized contacts. From our analysis we conclude that the differences in the histograms of these metals are due to i the very different electronic structures, which means different atomic orbitals contributing to the transport and ii the different mechanical properties, which in a case such as Pt lead to the formation of special structures, namely, monoatomic chains. Of particular interest are results for Ni that indicate the absence of any conductance quantization, and show how the current polarization evolves including large fluctuations from negative values in thick contacts to even positive values in the tunneling regime after rupture of the contact. Finally, we also present a detailed analysis of the breaking forces of these metallic contacts, which are compared to the forces predicted from bulk considerations.
TL;DR: In this article, the thermal boundary conductance of single-walled carbon nanotubes (SWNTs) was investigated using molecular dynamics simulations, and the expected high thermal conductivity was simulated by mixing 13 C isotope impurities to SWNTs or binding two SWNT with different chirality with a junction structure in between.
Abstract: Heat transfer of single-walled carbon nanotubes (SWNTs) in practical situations is investigated using molecular dynamics (MD) simulations. Attenuation of the expected high thermal conductivity was simulated by mixing 13 C isotope impurities to SWNTs or binding two SWNTs with different chirality with a junction structure in between. The heat transfer through the junction can be expressed with the thermal boundary conductance by considering a virtual boundary at the junction. The lateral heat conduction was compared with the thermal boundary conductance at the interfaces between an SWNT and surrounding materials. By applying the lumped capacity method on the non-stationary molecular dynamics simulations, the thermal boundary conductance of an SWNT bundle and an SWNT confining water were calculated. Finally, some conventional properties were estimated to characterize the anisotropic heat conduction.
TL;DR: Direct measurements of the conductance of single-Car molecules under potential control in a membrane-mimicking environment found that when Car are oxidized conductance is enhanced and the electronic decay constant (beta) is decreased, however, the neutral molecule may already be conductive enough to account for observed electron transfer rates.
Abstract: Carotenoids (Car) act as “wires” that discharge unwanted electrons in the reaction center of higher plants. One step in this “side-path” electron conduction is thought to be mediated by Car oxidation. We have carried out direct measurements of the conductance of single-Car molecules under potential control in a membrane-mimicking environment, and we found that when Car are oxidized conductance is enhanced and the electronic decay constant (β) is decreased. However, the neutral molecule may already be conductive enough to account for observed electron transfer rates.
TL;DR: It is observed subharmonic gap structure in the differential conductance and a distinct peak in the conductance at zero bias, which is interpreted as a manifestation of the supercurrent.
Abstract: We fabricated reproducible high transparency superconducting contacts consisting of superconducting $\mathrm{Ti}/\mathrm{Al}/\mathrm{Ti}$ trilayers to gated single-wall carbon nanotubes. The reported semiconducting single-wall carbon nanotubes have normal state differential conductance up to $3{e}^{2}/h$ and exhibit clear Fabry-Perot interference patterns in the bias spectroscopy plot. We observed subharmonic gap structure in the differential conductance and a distinct peak in the conductance at zero bias, which is interpreted as a manifestation of the supercurrent. The gate dependence of this supercurrent as well as the excess current are examined and compared to the coherent theory of superconducting quantum point contacts with good agreement.
TL;DR: In this article, the conductance of single 1,4-benzenedithiol (BDT) molecules is investigated in a wide range (0,03)G0, exploiting mechanically controllable break junction technique.
Abstract: Conductance of single 1,4-benzenedithiol (BDT) molecules is investigated in a wide range (0–03)G0, exploiting mechanically controllable break junction technique The authors observed a series of clear conductance steps both in low- (∼001G0) and high-conductance (∼01G0) regimes and corresponding two sets of peak structures in the conductance histograms The two distinct conductance states are attributable to different Au–S bonding configurations of Au∕BDT∕Au junctions The high-bias measurements reveal that the high-conductance state of single BDT molecules is stable up to 16V and prospective for molecular device applications
TL;DR: Electrochemical scanning tunneling microscopy and spectroscopy data obtained by two-dimensional electrochemical STS and STM imaging lead to the conclusion that electron transport occurs by thermally activated hopping, and the results suggest that electrons transport occurs in the adiabatic limit of strong electronic coupling.
Abstract: We used electrochemical scanning tunneling microscopy (STM) and spectroscopy (STS) to elucidate the mechanism of electron transport through individual pyridyl-based Os complexes. Our tunneling data obtained by two-dimensional electrochemical STS and STM imaging lead us to the conclusion that electron transport occurs by thermally activated hopping. The conductance enhancement around the redox potential of the complex, which is reminiscent of switching and transistor characterics in electronics, is reflected both in the STM imaging contrast and directly in the tunneling current. The latter shows a biphasic distance dependence, in line with a two-step electron hopping process. Under conditions where the substrate/molecule electron transfer (ET) step is dominant in determining the overall tunneling current, we determined the conductance of an individual Os complex to be 9 nS (Vbias = 0.1 V). We use theoretical approaches to connect the single-molecule conductance with electrochemical kinetics data obtained f...
TL;DR: In this paper, the intrinsic currentvoltage properties of a ZnO nanowire measured by a four-tip scanning tunneling microscopy (F-STM) were investigated.
Abstract: We report intrinsic current-voltage properties of ZnO nanowire measured by a four-tip scanning tunneling microscopy (F-STM). It is found that after bending the nanowire with the F-STM the conductance is reduced by about five orders of magnitude. The cathodoluminescent spectra indicate that the ZnO nanowires contain a sizable amount of defects in the surface region, responsible for their conduction. It is suggested that the observed huge conductance changes are caused by the shifting of the surface defect states in the ZnO nanowires in response to the applied surface strain.
TL;DR: Apparent conductance changes observed in sequential measurements suggest the existence of bond fluctuation among the adsorption sites.
Abstract: Conductance was measured for the single molecules with S/Se anchoring on a Au surface using the point contact method with scanning tunneling microscopy that enables us to selectively perform a repeated analysis of a chosen target molecule. Apparent conductance changes observed in sequential measurements suggest the existence of bond fluctuation among the adsorption sites.
TL;DR: In this paper, a procedure based on the recently developed ''adaptive'' time-dependent density matrix renormalization group (DMRG) technique is presented to calculate the zero temperature conductance of nanostructures, such as quantum dots (QDs) or molecular conductors, when represented by a small number of active levels.
Abstract: A procedure based on the recently developed ``adaptive'' time-dependent density-matrix-renormalization-group (DMRG) technique is presented to calculate the zero temperature conductance of nanostructures, such as quantum dots (QDs) or molecular conductors, when represented by a small number of active levels. The leads are modeled using noninteracting tight-binding Hamiltonians. The ground state at time zero is calculated at zero bias. Then, a small bias is applied between the two leads, the wave function is DMRG evolved in time, and currents are measured as a function of time. Typically, the current is expected to present periodicities over long times, involving intermediate well-defined plateaus that resemble steady states. The conductance can be obtained from those steady-state-like currents. To test this approach, several cases of interacting and noninteracting systems have been studied. Our results show excellent agreement with exact results in the noninteracting case. More importantly, the technique also reproduces quantitatively well-established results for the conductance and local density of states in both the cases of one and two coupled interacting QDs. The technique also works at finite bias voltages, and it can be extended to include interactions in the leads.