@article{17615, abstract = {Graham et al. have detected a 5.2 yr periodic optical variability of the quasar PG 1302-102 at redshift z = 0.3, which they interpret as the redshifted orbital period (1 + z)tbin of a putative supermassive black hole binary (SMBHB). Here, we consider the implications of a 3–8 times shorter orbital period, suggested by hydrodynamical simulations of circumbinary discs (CBDs) with nearly equal-mass SMBHBs (q ≡ M2/M1 ≳ 0.3). With the corresponding 2–4 times tighter binary separation, PG 1302 would be undergoing gravitational wave dominated inspiral, and serve as a proof that the BHs can be fuelled and produce bright emission even in this late stage of the merger. The expected fraction of binaries with the shorter tbin, among bright quasars, would be reduced by one to two orders of magnitude, compared to the 5.2 yr period, in better agreement with the rarity of candidates reported by Graham et al. Finally, shorter periods would imply higher binary speeds, possibly imprinting periodicity on the light curves from relativistic beaming, as well as measurable relativistic effects on the Fe K α line. The CBD model predicts additional periodic variability on time-scales of tbin and ≈0.5tbin, as well as periodic variation of broad line widths and offsets relative to the narrow lines, which are consistent with the observations. Future observations will be able to test these predictions and hence the binary+CBD hypothesis for PG 1302.}, author = {D'Orazio, D. J. and Haiman, Zoltán and Duffell, P. and Farris, B. D. and MacFadyen, A. I.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2540--2545}, publisher = {Oxford University Press}, title = {{A reduced orbital period for the supermassive black hole binary candidate in the quasar PG 1302-102?}}, doi = {10.1093/mnras/stv1457}, volume = {452}, year = {2015}, } @article{17622, abstract = {Graham et al. discovered a supermassive black hole binary (SMBHB) candidate and identified the detected 5.2 yr period of the optical variability as the orbital period of the binary. Hydrodynamical simulations predict multiple periodic components for the variability of SMBHBs, thus raising the possibility that the true period of the binary is different from 5.2 yr. We analyse the periodogram of PG1302 and find no compelling evidence for additional peaks. We also point out that, despite the 5.2 yr peak being significant if a single source is considered, further analysis is required to account for the fact that PG1302 was selected among a large sample of 247 000 quasars. We derive upper limits on any additional periodic modulations in the available data, by modelling the light curve as the sum of stochastic noise and the known 5.2 yr periodic component, and injecting additional sinusoidal signals. We find that, with the current data, we would be able to detect with high significance (false alarm probability <1 per cent) secondary periodic terms, with periods in the range predicted by the simulations, if the amplitude of the variability was at least ∼0.06 mag (compared to 0.14 mag for the main sinusoid). A three-year follow-up monitoring campaign with weekly observations can increase the sensitivity for detecting secondary peaks by ≈50 per cent, and would allow a more robust test of predictions from hydrodynamical simulations.}, author = {Charisi, M. and Bartos, I. and Haiman, Zoltán and Price-Whelan, A. M. and Márka, S.}, issn = {1745-3933}, journal = {Monthly Notices of the Royal Astronomical Society: Letters}, number = {1}, pages = {L21--L25}, publisher = {Oxford University Press}, title = {{Multiple periods in the variability of the supermassive black hole binary candidate quasar PG1302-102?}}, doi = {10.1093/mnrasl/slv111}, volume = {454}, year = {2015}, } @article{17641, abstract = {In order to elucidate the origin of spin in both dark matter and baryons in galaxies, we have performed hydrodynamical simulations from cosmological initial conditions. We study atomic cooling haloes in the redshift range 100>z>9 with masses of order 109M⊙ at redshift z=10. We assume that the gas has primordial composition and that H2-cooling and prior star-formation in the haloes have been suppressed. We present a comprehensive analysis of the gas and dark matter properties of four halos with very low (λ≈0.01), low (λ≈0.04), high (λ≈0.06) and very high (λ≈0.1) spin parameter. Our main conclusion is that the spin orientation and magnitude is initially well described by tidal torque linear theory, but later on is determined by the merging and accretion history of each halo. We provide evidence that the topology of the merging region, i.e. the number of colliding filaments, gives an accurate prediction for the spin of dark matter and gas: halos at the center of knots will have low spin while those in the center of filaments will have high spin. The spin of a halo is given by λ≈0.05×(7.6/numberoffilaments)^5.1}, author = {Prieto, Joaquin and Jimenez, Raul and Haiman, Zoltán and González, Roberto E.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, pages = {784--802}, publisher = {Oxford University Press}, title = {{The origin of spin in galaxies: Clues from simulations of atomic cooling haloes}}, doi = {10.1093/mnras/stv1234}, volume = {452}, year = {2015}, } @article{17652, abstract = {Because most large galaxies contain a central black hole, and galaxies often merge, black-hole binaries are expected to be common in galactic nuclei. Although they cannot be imaged, periodicities in the light curves of quasars have been interpreted as evidence for binaries, most recently in PG~1302-102, with a short rest-frame optical period of 4 years. If the orbital period matches this value, then for the range of estimated black hole masses the components would be separated by 0.007-0.017 pc, implying relativistic orbital speeds. There has been much debate over whether black hole orbits could be smaller than 1 pc. Here we show that the amplitude and the sinusoid-like shape of the variability of PG~1302-102 can be fit by relativistic Doppler boosting of emission from a compact, steadily accreting, unequal-mass binary. We predict that brightness variations in the ultraviolet light curve track those in the optical, but with a 2-3 times larger amplitude. This prediction is relatively insensitive to the details of the emission process, and is consistent with archival UV data. Follow-up UV and optical observations in the next few years can test this prediction and confirm the existence of a binary black hole in the relativistic regime.}, author = {D'Orazio, Daniel J. and Haiman, Zoltán and Schiminovich, David}, issn = {0028-0836}, journal = {Nature}, number = {7569}, pages = {351--353}, publisher = {Springer Science and Business Media LLC}, title = {{Relativistic boost as the cause of periodicity in a massive black-hole binary candidate}}, doi = {10.1038/nature15262}, volume = {525}, year = {2015}, } @article{17663, abstract = {Recently, Planck measured a value of the cosmic microwave background (CMB) optical depth due to electron scattering of τ=0.066±0.016. Here we show that this low value leaves essentially no room for an early partial reionisation of the intergalactic medium (IGM) by high-redshift Population III (Pop III) stars, expected to have formed in low-mass minihaloes. We perform semi-analytic calculations of reionisation which include the contribution from Pop II stars in atomic cooling haloes, calibrated with high-redshift galaxy observations, and Pop III stars in minihaloes with feedback due to Lyman-Werner (LW) radiation and metal enrichment. We find that without LW feedback or prompt metal enrichment (and assuming a minihalo escape fraction of 0.5) the Pop III star formation efficiency cannot exceed ∼a few×10−4, without violating the constraints set by Planck data. This excludes massive Pop III star formation in typical 106M⊙ minihaloes. Including LW feedback and metal enrichment alleviates this tension, allowing large Pop III stars to form early on before they are quenched by feedback. We find that the total density of Pop III stars formed across cosmic time is ≲104−5 M⊙ Mpc−3 and does not depend strongly on the feedback prescription adopted. Additionally, we perform a simple estimate of the possible impact on reionisation of X-rays produced by accretion onto black hole remnants of Pop III stars. We find that unless the accretion duty cycle is very low (≲0.01), this could lead to an optical depth inconsistent with Planck.}, author = {Visbal, Eli and Haiman, Zoltán and Bryan, Greg L.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {4457--4467}, publisher = {Oxford University Press}, title = {{Limits on population III star formation in minihaloes implied by Planck}}, doi = {10.1093/mnras/stv1941}, volume = {453}, year = {2015}, } @article{17685, abstract = {We propose an observational test for gravitationally recoiling supermassive black holes (BHs) in active galactic nuclei, based on a correlation between the velocities of BHs relative to their host galaxies, |\Delta v|, and their obscuring dust column densities, \Sigma_{dust} (both measured along the line of sight). We use toy models for the distribution of recoil velocities, BH trajectories, and the geometry of obscuring dust tori in galactic centres, to simulate 2.5x10^5 random observations of recoiling quasars. BHs with recoil velocities comparable to the escape velocity from the galactic centre remain bound to the nucleus, and do not fully settle back to the centre of the torus due to dynamical friction in a typical quasar lifetime. We find that |\Delta v| and \Sigma_ {dust} for these BHs are positively correlated. For obscured (\Sigma_{dust}>0) and for partially obscured (0<\Sigma_{dust}<~2.3 g/m^2) quasars with |\Delta v|>=45 km/s, the sample correlation coefficient between log10(|\Delta v|) and \Sigma_{dust} is r_{45} = 0.28+/-0.02 and r_{45} = 0.13+/-0.02, respectively. Allowing for random +/-100 km/s errors in |\Delta v| unrelated to the recoil dilutes the correlation for the partially obscured quasars to r_{45} = 0.026+/-0.004 measured between |\Delta v| and \Sigma_{dust}. A random sample of >~3,500 obscured quasars with |\Delta v|>=45 km/s would allow rejection of the no-correlation hypothesis with 3 sigma significance 95% of the time. Finally, we find that the fraction of obscured quasars, F_{obs}(|\Delta v|), decreases with |\Delta v| from F_{obs}(<10 km/s)>~0.8 to F_{obs}(>10^3 km/s)<~0.4. This predicted trend can be compared to the observed fraction of type II quasars, and can further test combinations of recoil, trajectory, and dust torus models.}, author = {Raffai, P. and Haiman, Zoltán and Frei, Z.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, pages = {484--492}, publisher = {Oxford University Press}, title = {{A statistical method to search for recoiling supermassive black holes in active galactic nuclei}}, doi = {10.1093/mnras/stv2371}, volume = {455}, year = {2015}, } @article{17694, abstract = {Constraining the properties of Population III (Pop III) stars will be very challenging because they reside in small galaxies at high redshift which will be difficult to directly detect. In this paper, we suggest that intensity mapping may be a promising method to study Pop III stars. Intensity mapping is a technique proposed to measure large-scale fluctuations of galaxy line emission in three dimensions without resolving individual sources. This technique is well suited for observing many faint galaxies because it can measure their cumulative emission even if they cannot be directly detected. We focus on intensity mapping of He ii recombination lines. These lines are much stronger in Pop III stars than Pop II stars because the harder spectra of Pop III stars are expected to produce many He ii ionizing photons. Measuring the He ii 1640 Å intensity mapping signal, along with the signals from other lines such as Lyα, Hα, and metal lines, could give constraints on the initial mass function (IMF) and star formation rate density of Pop III stars as a function of redshift. To demonstrate the feasibility of these observations, we estimate the strength of the Pop III He ii 1640 Å intensity mapping signal from z = 10–20. We show that at z ≈ 10, the signal could be measured accurately by two different hypothetical future instruments, one which cross-correlates He ii 1640 Å with CO(1–0) line emission from galaxies and the other with 21 cm emission from the intergalactic medium.}, author = {Visbal, Eli and Haiman, Zoltán and Bryan, Greg L.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2506--2513}, publisher = {Oxford University Press}, title = {{Looking for Population III stars with He ii line intensity mapping}}, doi = {10.1093/mnras/stv785}, volume = {450}, year = {2015}, } @article{17702, abstract = {Weak gravitational lensing is a powerful cosmological probe, with non--Gaussian features potentially containing the majority of the information. We examine constraints on the parameter triplet (Ωm,w,σ8) from non-Gaussian features of the weak lensing convergence field, including a set of moments (up to 4th order) and Minkowski functionals, using publicly available data from the 154deg2 CFHTLenS survey. We utilize a suite of ray--tracing N-body simulations spanning 91 points in (Ωm,w,σ8) parameter space, replicating the galaxy sky positions, redshifts and shape noise in the CFHTLenS catalogs. We then build an emulator that interpolates the simulated descriptors as a function of (Ωm,w,σ8), and use it to compute the likelihood function and parameter constraints. We employ a principal component analysis to reduce dimensionality and to help stabilize the constraints with respect to the number of bins used to construct each statistic. Using the full set of statistics, we find Σ8≡σ8(Ωm/0.27)^0.55=0.75±0.04 (68% C.L.), in agreement with previous values. We find that constraints on the (Ωm,σ8) doublet from the Minkowski functionals suffer a strong bias. However, high-order moments break the (Ωm,σ8) degeneracy and provide a tight constraint on these parameters with no apparent bias. The main contribution comes from quartic moments of derivatives.}, author = {Petri, Andrea and Liu, Jia and Haiman, Zoltán and May, Morgan and Hui, Lam and Kratochvil, Jan M.}, issn = {1550-7998}, journal = {Physical Review D}, number = {10}, publisher = {American Physical Society}, title = {{Emulating the CFHTLenS weak lensing data: Cosmological constraints from moments and Minkowski functionals}}, doi = {10.1103/physrevd.91.103511}, volume = {91}, year = {2015}, } @article{17710, abstract = {Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the 154 deg^2 CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models, covering broad ranges of the three parameters Ωm, σ8, and w, and replicating the Galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build an emulator that interpolates the power spectrum and the peak counts to an accuracy of ≤5%, and compute the likelihood in the three-dimensional parameter space (Ωm, σ8, w) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the power spectrum and peak counts are combined, the area of the error "banana'' in the (Ωm, σ8) plane reduces by a factor of ≈2, compared to using the power spectrum alone. For a flat Λ cold dark matter model, combining both statistics, we obtain the constraint σ8(Ωm/0.27)^0.63=0.85+0.03−0.03.}, author = {Liu, Jia and Petri, Andrea and Haiman, Zoltán and Hui, Lam and Kratochvil, Jan M. and May, Morgan}, issn = {1550-7998}, journal = {Physical Review D}, number = {6}, publisher = {American Physical Society}, title = {{Cosmology constraints from the weak lensing peak counts and the power spectrum in CFHTLenS data}}, doi = {10.1103/physrevd.91.063507}, volume = {91}, year = {2015}, } @article{1788, abstract = {We fabricate and characterize a microscale silicon opto-electromechanical system whose mechanical motion is coupled capacitively to an electrical circuit and optically via radiation pressure to a photonic crystal cavity. To achieve large electromechanical interaction strength, we implement an inverse shadow mask fabrication scheme which obtains capacitor gaps as small as 30 nm while maintaining a silicon surface quality necessary for minimizing optical loss. Using the sensitive optical read-out of the photonic crystal cavity, we characterize the linear and nonlinear capacitive coupling to the fundamental ωm=2π = 63 MHz in-plane flexural motion of the structure, showing that the large electromechanical coupling in such devices may be suitable for realizing efficient microwave-to-optical signal conversion.}, author = {Pitanti, Alessandro and Fink, Johannes M and Safavi Naeini, Amir and Hill, Jeff and Lei, Chan and Tredicucci, Alessandro and Painter, Oskar}, issn = {1094-4087}, journal = {Optics Express}, number = {3}, pages = {3196 -- 3208}, publisher = {Optica Publishing Group}, title = {{Strong opto-electro-mechanical coupling in a silicon photonic crystal cavity}}, doi = {10.1364/OE.23.003196}, volume = {23}, year = {2015}, } @article{1789, abstract = {Intellectual disability (ID) has an estimated prevalence of 2-3%. Due to its extreme heterogeneity, the genetic basis of ID remains elusive in many cases. Recently, whole exome sequencing (WES) studies revealed that a large proportion of sporadic cases are caused by de novo gene variants. To identify further genes involved in ID, we performed WES in 250 patients with unexplained ID and their unaffected parents and included exomes of 51 previously sequenced child-parents trios in the analysis. Exome analysis revealed de novo intragenic variants in SET domain-containing 5 (SETD5) in two patients. One patient carried a nonsense variant, and the other an 81 bp deletion located across a splice-donor site. Chromosomal microarray diagnostics further identified four de novo non-recurrent microdeletions encompassing SETD5. CRISPR/Cas9 mutation modelling of the two intragenic variants demonstrated nonsense-mediated decay of the resulting transcripts, pointing to a loss-of-function (LoF) and haploinsufficiency as the common disease-causing mechanism of intragenic SETD5 sequence variants and SETD5-containing microdeletions. In silico domain prediction of SETD5, a predicted SET domain-containing histone methyltransferase (HMT), substantiated the presence of a SET domain and identified a novel putative PHD domain, strengthening a functional link to well-known histone-modifying ID genes. All six patients presented with ID and certain facial dysmorphisms, suggesting that SETD5 sequence variants contribute substantially to the microdeletion 3p25.3 phenotype. The present report of two SETD5 LoF variants in 301 patients demonstrates a prevalence of 0.7% and thus SETD5 variants as a relatively frequent cause of ID.}, author = {Kuechler, Alma and Zink, Alexander and Wieland, Thomas and Lüdecke, Hermann and Cremer, Kirsten and Salviati, Leonardo and Magini, Pamela and Najafi, Kimia and Zweier, Christiane and Czeschik, Johanna and Aretz, Stefan and Endele, Sabine and Tamburrino, Federica and Pinato, Claudia and Clementi, Maurizio and Gundlach, Jasmin and Maylahn, Carina and Mazzanti, Laura and Wohlleber, Eva and Schwarzmayr, Thomas and Kariminejad, Roxana and Schlessinger, Avner and Wieczorek, Dagmar and Strom, Tim and Novarino, Gaia and Engels, Hartmut}, journal = {European Journal of Human Genetics}, number = {6}, pages = {753 -- 760}, publisher = {Nature Publishing Group}, title = {{Loss-of-function variants of SETD5 cause intellectual disability and the core phenotype of microdeletion 3p25.3 syndrome}}, doi = {10.1038/ejhg.2014.165}, volume = {23}, year = {2015}, } @article{1792, abstract = {Motivated by recent ideas of Harman (Unif. Distrib. Theory, 2010) we develop a new concept of variation of multivariate functions on a compact Hausdorff space with respect to a collection D of subsets. We prove a general version of the Koksma-Hlawka theorem that holds for this notion of variation and discrepancy with respect to D. As special cases, we obtain Koksma-Hlawka inequalities for classical notions, such as extreme or isotropic discrepancy. For extreme discrepancy, our result coincides with the usual Koksma-Hlawka theorem. We show that the space of functions of bounded D-variation contains important discontinuous functions and is closed under natural algebraic operations. Finally, we illustrate the results on concrete integration problems from integral geometry and stereology.}, author = {Pausinger, Florian and Svane, Anne}, journal = {Journal of Complexity}, number = {6}, pages = {773 -- 797}, publisher = {Academic Press}, title = {{A Koksma-Hlawka inequality for general discrepancy systems}}, doi = {10.1016/j.jco.2015.06.002}, volume = {31}, year = {2015}, } @article{1793, abstract = {We present a software platform for reconstructing and analyzing the growth of a plant root system from a time-series of 3D voxelized shapes. It aligns the shapes with each other, constructs a geometric graph representation together with the function that records the time of growth, and organizes the branches into a hierarchy that reflects the order of creation. The software includes the automatic computation of structural and dynamic traits for each root in the system enabling the quantification of growth on fine-scale. These are important advances in plant phenotyping with applications to the study of genetic and environmental influences on growth.}, author = {Symonova, Olga and Topp, Christopher and Edelsbrunner, Herbert}, journal = {PLoS One}, number = {6}, publisher = {Public Library of Science}, title = {{DynamicRoots: A software platform for the reconstruction and analysis of growing plant roots}}, doi = {10.1371/journal.pone.0127657}, volume = {10}, year = {2015}, } @article{17965, abstract = {We investigate bidirectional femtosecond charge transfer dynamics using the core–hole clock implementation of resonant photoemission spectroscopy from 4,4′-bipyridine molecular layers on three different surfaces: Au(111), epitaxial graphene on Ni(111), and graphene nanoribbons. We show that the lowest unoccupied molecular orbital (LUMO) of the molecule drops partially below the Fermi level upon core–hole creation in all systems, opening an additional decay channel for the core–hole, involving electron donation from substrate to the molecule. Furthermore, using the core–hole clock method, we find that the bidirectional charge transfer time between the substrate and the molecule is fastest on Au(111), with a 2 fs time, then around 4 fs for epitaxial graphene and slowest with graphene nanoribbon surface, taking around 10 fs. Finally, we provide evidence for fast phase decoherence of the core-excited LUMO* electron through an interaction with the substrate providing the first observation of such a fast bidirectional charge transfer across an organic/graphene interface.}, author = {Adak, Olgun and Kladnik, Gregor and Bavdek, Gregor and Cossaro, Albano and Morgante, Alberto and Cvetko, Dean and Venkataraman, Latha}, issn = {1530-6992}, journal = {Nano Letters}, number = {12}, pages = {8316--8321}, publisher = {American Chemical Society}, title = {{Ultrafast bidirectional charge transport and electron decoherence at molecule/surface interfaces: A comparison of gold, graphene, and graphene nanoribbon surfaces}}, doi = {10.1021/acs.nanolett.5b03962}, volume = {15}, year = {2015}, } @article{17966, author = {Strange, Mikkel and Solomon, Gemma C. and Venkataraman, Latha and Campos, Luis M.}, issn = {1530-6992}, journal = {Nano Letters}, number = {11}, pages = {7177--7178}, publisher = {American Chemical Society}, title = {{Reply to “Comment on ‘Breakdown of Interference Rules in Azulene, a Nonalternant Hydrocarbon’”}}, doi = {10.1021/acs.nanolett.5b04154}, volume = {15}, year = {2015}, } @article{17967, abstract = {We report a systematic computational search of molecular frameworks for intrinsic rectification of electron transport. The screening of molecular rectifiers includes 52 molecules and conformers spanning over 9 series of structural motifs. N-Phenylbenzamide is found to be a promising framework with both suitable conductance and rectification properties. A targeted screening performed on 30 additional derivatives and conformers of N-phenylbenzamide yielded enhanced rectification based on asymmetric functionalization. We demonstrate that electron-donating substituent groups that maintain an asymmetric distribution of charge in the dominant transport channel (e.g., HOMO) enhance rectification by raising the channel closer to the Fermi level. These findings are particularly valuable for the design of molecular assemblies that could ensure directionality of electron transport in a wide range of applications, from molecular electronics to catalytic reactions.}, author = {Ding, Wendu and Koepf, Matthieu and Koenigsmann, Christopher and Batra, Arunabh and Venkataraman, Latha and Negre, Christian F. A. and Brudvig, Gary W. and Crabtree, Robert H. and Schmuttenmaer, Charles A. and Batista, Victor S.}, issn = {1549-9626}, journal = {Journal of Chemical Theory and Computation}, number = {12}, pages = {5888--5896}, publisher = {American Chemical Society}, title = {{Computational design of intrinsic molecular rectifiers based on asymmetric functionalization of N-Phenylbenzamide}}, doi = {10.1021/acs.jctc.5b00823}, volume = {11}, year = {2015}, } @article{17968, abstract = {While the electrical conductivity of bulk-scale group 14 materials such as diamond carbon, silicon, and germanium is well understood, there is a gap in knowledge regarding the conductivity of these materials at the nano and molecular scales. Filling this gap is important because integrated circuits have shrunk so far that their active regions, which rely so heavily on silicon and germanium, begin to resemble ornate molecules rather than extended solids. Here we unveil a new approach for synthesizing atomically discrete wires of germanium and present the first conductance measurements of molecular germanium using a scanning tunneling microscope-based break-junction (STM-BJ) technique. Our findings show that germanium and silicon wires are nearly identical in conductivity at the molecular scale, and that both are much more conductive than aliphatic carbon. We demonstrate that the strong donor ability of C–Ge σ-bonds can be used to raise the energy of the anchor lone pair and increase conductance. Furthermore, the oligogermane wires behave as conductance switches that function through stereoelectronic logic. These devices can be trained to operate with a higher switching factor by repeatedly compressing and elongating the molecular junction.}, author = {Su, Timothy A. and Li, Haixing and Zhang, Vivian and Neupane, Madhav and Batra, Arunabh and Klausen, Rebekka S. and Kumar, Bharat and Steigerwald, Michael L. and Venkataraman, Latha and Nuckolls, Colin}, issn = {1520-5126}, journal = {Journal of the American Chemical Society}, number = {38}, pages = {12400--12405}, publisher = {American Chemical Society}, title = {{Single-molecule conductance in atomically precise Germanium wires}}, doi = {10.1021/jacs.5b08155}, volume = {137}, year = {2015}, } @article{17969, abstract = {Recent experiments have shown that transport properties of molecular-scale devices can be reversibly altered by the surrounding solvent. Here, we use a combination of first-principles calculations and experiment to explain this change in transport properties through a shift in the local electrostatic potential at the junction caused by nearby conducting and solvent molecules chemically bound to the electrodes. This effect is found to alter the conductance of 4,4′-bipyridine-gold junctions by more than 50%. Moreover, we develop a general electrostatic model that quantitatively relates the conductance and dipoles associated with the bound solvent and conducting molecules. Our work shows that solvent-induced effects can be used to control charge and energy transport at molecular-scale interfaces.}, author = {Kotiuga, Michele and Darancet, Pierre and Arroyo, Carlos R. and Venkataraman, Latha and Neaton, Jeffrey B.}, issn = {1530-6992}, journal = {Nano Letters}, number = {7}, pages = {4498--4503}, publisher = {American Chemical Society}, title = {{Adsorption-induced solvent-based electrostatic gating of charge transport through molecular junctions}}, doi = {10.1021/acs.nanolett.5b00990}, volume = {15}, year = {2015}, } @article{17970, abstract = {Charge transport properties of metal–molecule interfaces depend strongly on the character of molecule–electrode interactions. Although through-bond coupled systems have attracted the most attention, through-space coupling is important in molecular systems when, for example, through-bond coupling is suppressed due to quantum interference effects. To date, a probe that clearly distinguishes these two types of coupling has not yet been demonstrated. Here, we investigate the origin of flicker noise in single molecule junctions and demonstrate how the character of the molecule–electrode coupling influences the flicker noise behavior of single molecule junctions. Importantly, we find that flicker noise shows a power law dependence on conductance in all junctions studied with an exponent that can distinguish through-space and through-bond coupling. Our results provide a new and powerful tool for probing and understanding coupling at the metal-molecule interface.}, author = {Adak, Olgun and Rosenthal, Ethan and Meisner, Jeffery and Andrade, Erick F. and Pasupathy, Abhay N. and Nuckolls, Colin and Hybertsen, Mark S. and Venkataraman, Latha}, issn = {1530-6992}, journal = {Nano Letters}, number = {6}, pages = {4143--4149}, publisher = {American Chemical Society}, title = {{Flicker noise as a probe of electronic interaction at metal–single molecule interfaces}}, doi = {10.1021/acs.nanolett.5b01270}, volume = {15}, year = {2015}, } @article{17971, abstract = {We study the impact of electrode band structure on transport through single-molecule junctions by measuring the conductance of pyridine-based molecules using Ag and Au electrodes. Our experiments are carried out using the scanning tunneling microscope based break-junction technique and are supported by density functional theory based calculations. We find from both experiments and calculations that the coupling of the dominant transport orbital to the metal is stronger for Au-based junctions when compared with Ag-based junctions. We attribute this difference to relativistic effects, which result in an enhanced density of d-states at the Fermi energy for Au compared with Ag. We further show that the alignment of the conducting orbital relative to the Fermi level does not follow the work function difference between two metals and is different for conjugated and saturated systems. We thus demonstrate that the details of the molecular level alignment and electronic coupling in metal–organic interfaces do not follow simple rules but are rather the consequence of subtle local interactions.}, author = {Adak, Olgun and Korytár, Richard and Joe, Andrew Y. and Evers, Ferdinand and Venkataraman, Latha}, issn = {1530-6992}, journal = {Nano Letters}, number = {6}, pages = {3716--3722}, publisher = {American Chemical Society}, title = {{Impact of electrode density of states on transport through pyridine-linked single molecule junctions}}, doi = {10.1021/acs.nanolett.5b01195}, volume = {15}, year = {2015}, }