Secondary Hydrogen Isotopes Effects. III. Acetolysis of endoand exo-Norbornyl-5,6-d2 p-Bromobenzenesulfonates

The synthesis of endo- and exo-norbornyl-5,6-d2 p-br omobenzenesulfonates is d escribed. The rate constants of the acetolysis were measured a nd an isotope effect was obser v ed in the rea ction of the exo-isomer. This result is in agreement with the mechanism proposed by Roberts and indicates that the 1,3-hydride shift o ccurs in the rate determining step

Secondary Hydrogen Isotope Effects. VII. Ethanolysis Rates of 1,1-Dimethylallyl-3,3-d2 Chloride and 3,3-Dimethylallyl-1,1-d2 Chloride

Primary aind tertiary dimethylallyl chlorides deuterated at either the alpha or gamma pos~tion were prepared a:nd subjected to e.thanolysis. A kinetic isotope effect (kt1/kn) of 1.20 was observed in the reaction of the primary isomer while rthe tertiary chloride reacted at the same rate as the undeuterated analog,. The absence of an isotope effect in the latter case is explained by the lack of sp3 - sp2 rehybridization of the carbon-deuterium bonds in the rate determining step

Quasi two-dimensional Fermi surface topography of the delafossite PdRhO2

The authors acknowledge the financial support from the European Research Council (through the QUESTDO project), the Engineering and Physical Sciences Research Council UK (Grants No. EP/I031014/1 and No. EP/L015110/1), the Royal Society, and the Max-Planck Society.We report on a combined study of the de Haas-van Alphen effect and angle resolved photoemission spectroscopy on single crystals of the metallic delafossite PdRhO2 rounded off by ab initio band structure calculations. A high sensitivity torque magnetometry setup with SQUID readout and synchrotron-based photoemission with a light spot size of ~50μm enabled high resolution data to be obtained from samples as small as 150 × 100 × 20(μm)3. The Fermi surface shape is nearly cylindrical with a rounded hexagonal cross section enclosing a Luttinger volume of 1.00(1) electrons per formula unit.PostprintPeer reviewe

The Lorenz ratio as a guide to scattering contributions to Planckian transport

In many physical situations in which many-body assemblies exist at temperature $T$, a characteristic quantum-mechanical time scale of approximately $\hbar/k_{B}T$ can be identified in both theory and experiment, leading to speculation that it may be the shortest meaningful time in such circumstances. When this behaviour is investigated by probing the scattering rate of strongly interacting electrons in metals, it is clear that in some cases only electron-electron scattering can be its cause, while in others it arises from high-temperature scattering of electrons from quantised lattice vibrations, i.e. phonons. In metallic oxides, which are among the most studied materials, analysis of electrical transport does not satisfactorily identify the relevant scattering mechanism at 'high' temperatures near room temperature. We employ a contactless optical method to measure thermal diffusivity in two Ru-based layered perovskites, Sr$_3$Ru$_2$O$_7$ and Sr$_2$RuO$_4$, and use the measurements to extract the dimensionless Lorenz ratio. By comparing our results to the literature data on both conventional and unconventional metals we show how the analysis of high-temperature thermal transport can both give important insight into dominant scattering mechanisms, and be offered as a stringent test of theories attempting to explain anomalous scattering.Comment: 27 pages, 8 figure

Remote digital forensics practices

In this paper, the idea of remote digital forensics is introduced, its benefits and possible drawbacks are presented. It is important to understand it is more a recognition of existing state of the affairs than introducing a new concept. Various aspects of forensically sound remote approach are described with references to tools and practices. Relations to other digital forensic fields are presented and highlighted with aim to recognize distributed work and parallelism in modern digital forensic as existing practice close to remote forensics

Metal-Insulator Transition in the Two-Dimensional Hubbard Model at Half-Filling with Lifetime Effects within the Moment Approach

We explore the effect of the imaginary part of the self-energy, $Im\Sigma(\vec{k},\omega)$, having a single pole, $\Omega(\vec{k},\omega)$, with spectral weight, $\alpha(\vec{k})$, and quasi-particle lifetime, $\Gamma(\vec{k})$, on the density of states. We solve the set of parameters, $\Omega(\vec{k},\omega$), $\alpha(\vec{k})$, and $\Gamma(\vec{k})$ by means of the moment approach (exact sum rules) of Nolting. Our choice for $\Sigma(k,\omega)$, satisfies the Kramers - Kronig relationship automatically. Due to our choice of the self - energy, the system is not a Fermi liquid for any value of the interaction, a result which is also true in the moment approach of Nolting without lifetime effects. By increasing the value of the local interaction, $U/W$, at half-filling ($\rho = 1/2$), we go from a paramagnetic metal to a paramagnetic insulator, (Mott metal - insulator transition ($MMIT$)) for values of $U/W$ of the order of $U/W \geq 1$ ($W$ is the band width) which is in agreement with numerical results for finite lattices and for infinity dimensions ($D = \infty$). These results settle down the main weakness of the spherical approximation of Nolting: a finite gap for any finite value of the interaction, i.e., an insulator for any finite value of $U/W$. Lifetime effects are absolutely indispensable. Our scheme works better than the one of improving the narrowing band factor, $B(\vec{k})$, beyond the spherical approximation of Nolting.Comment: 5 pages and 5 ps figures (included

Spin-valley locking in the normal state of a transition-metal dichalcogenide superconductor

We gratefully acknowledge support from the Engineering and Physical Sciences Research Council, UK (work at St Andrews under Grant No. EP/I031014/1 and work at Warwick under Grant No. EP/M028771/1) and the International Max Planck partnership. PDCK acknowledges support from the Royal Society through a University Research Fellowship. MSB was supported by the Grant-in-Aid for Scientific Research (S) (No. 24224009) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. LB, JR, and VS acknowledge studentship funding from EPSRC through grant nos. EP/G03673X/1, EP/L505079/1, and EP/L015110/1, respectively. The experiments at MAX IV Laboratory were made possible through funding from the Swedish Research Council and the Knut and Alice Wallenberg Foundation.Metallic transition-metal dichalcogenides (TMDCs) are benchmark systems for studying and controlling intertwined electronic orders in solids, with superconductivity developing from a charge density-wave state. The interplay between such phases is thought to play a critical role in the unconventional superconductivity of cuprates, Fe-based, and heavy-fermion systems, yet even for the more moderately-correlated TMDCs, their nature andorigins have proved controversial. Here, we study a prototypical example, 2H-NbSe2, by spin-and angle-resolved photoemission and first-principles theory. We find that the normal state,from which its hallmark collective phases emerge, is characterised by quasiparticles whose spin is locked to their valley pseudospin. This results from a combination of strong spin-orbit interactions and local inversion symmetry breaking, while interlayer coupling further drives a rich three-dimensional momentum dependence of the underlying Fermi surface spintexture. These findings necessitate a re-investigation of the nature of charge order and superconducting pairing in NbSe2 and related TMDCs.Publisher PDFPeer reviewe

Probing spin correlations using angle-resolved photoemission in a coupled metallic/Mott insulator system

Funding: European Research Council (Grant Nos. ERC-714193-QUESTDO and ERC-319286-QMAC), the Royal Society, the Leverhulme Trust (Grant Nos. RL-2016-006 and PLP-2015-144R); EPSRC for PhD studentship support through grant numbers EP/L015110/1 and EP/K503162/1. I.M. acknowledges PhD studentship support from the IMPRS for the Chemistry and Physics of Quantum MaterialsA nearly free electron metal and a Mott insulating state can be thought of as opposite ends of the spectrum of possibilities for the motion of electrons in a solid. Understanding their interaction lies at the heart of the correlated electron problem. In the magnetic oxide metal PdCrO2, nearly free and Mott-localized electrons exist in alternating layers, forming natural heterostructures. Using angle-resolved photoemission spectroscopy, quantitatively supported by a strong coupling analysis, we show that the coupling between these layers leads to an “intertwined” excitation that is a convolution of the charge spectrum of the metallic layer and the spin susceptibility of the Mott layer. Our findings establish PdCrO2 as a model system in which to probe Kondo lattice physics and also open new routes to use the a priori nonmagnetic probe of photoemission to gain insights into the spin susceptibility of correlated electron materials.Publisher PDFPeer reviewe

Idea Crowdsourcing in Public Sector – Proof-of-Concept Study

Following the most innovative cities of the world, City of Zagreb started in February 2017 the pilot project “Zagreb – Innovative City”. Pilot project is aimed to prove that the advance of the communication between the city administration and public (citizens, experts, businesses) is possible via social media network for crowdsourcing of innovative ideas. Implementation of the service gathering and converting ideas to beneficial projects should improve: • services for the citizens as well as • city administration efficiency. The application www.zg-inovacija.eu was developed in March 2017 and run as a pilot, intended to be a “proof-of-concept” during the period for three months (April-June 2017). Three areas of experimentation with consequent test outcomes were foreseen: 1. Level of public engagement – proved to be sufficient 2. Responsiveness of city structures in term of efficiency and effectiveness – demonstrated substantial improvement potential 3. Technological capability check – both development and operating were fully successful The evidence for City of Zagreb responsiveness improvement potential is the fact that in the pilot project three months course not a one idea - among almost 200 submitted in total – was streamlined as an official city project. As conclusion the author brings three main recommendations areas for implementing permanent service of idea crowdsourcing, stressing as very positive the acceptance of implementing this innovative project by the City of Zagreb