We have fabricated very flexible pentacene field-effect transistors with polyimide gate dielectric layers on plastic films with a mobility of 0.3cm2∕Vs and an on/off ratio of 105, and have measured their electrical properties under various compressive and tensile strains while changing the bending radius of the base plastic films systematically. We have found that the change in source-drain current with bending radius is reproducible and reversible when the bending radius is above 4.6mm, which corresponds to strains of ∼1.4±0.1%. Furthermore, the change in source-drain current does not depend on the direction of strain versus direction of current flow.

New model-independent compact representations of imaginary-time data are presented in terms of the intermediate representation (IR) of analytical continuation. We demonstrate the efficiency of the IR through continuous-time quantum Monte Carlo calculations of an Anderson impurity model. We find that the IR yields a significantly compact form of various types of correlation functions. This allows the direct quantum Monte Carlo measurement of Green's functions in a compressed form, which considerably reduces the computational cost and memory usage. Furthermore, the present framework will provide general ways to boost the power of cutting-edge diagrammatic/quantum Monte Carlo treatments of many-body systems.

We investigated the electronic and magnetic properties of the pyrochlore oxide Cd2Os2O7 using the density-functional theory plus on-site repulsion (U ) method, and depict the ground-state phase diagram with respect to U . We conclude that the all-in/all-out non-collinear magnetic order is stable in a wide range of U . We also show that the easy-axis anisotropy arising from the spin-orbit (SO) coupling plays a significant role in stabilizing the all-in/all-out magnetic order. A pseudo gap was observed near the transition between the antiferromagnetic metallic and insulating phases. Finally, we discuss possible origins of the peculiar low-temperature(T ) properties observed in experiments. PACS numbers: 75.47.Lx,71.15.Mb,71.70.Ej Pyrochlore transition-metal oxides A 2 B 2 O 7 are a class of materials that have been extensively investigated for several decades [1]. Recently, particular attention has been paid to 5d transition-metal oxides, such as iridates (A 2 Ir 2 O 7 ), in search for unconventional phenomena that are induced by the competing spin-orbit (SO) coupling and electron correlation.Cd 2 Os 2 O 7 is one of the few compounds whose low-T magnetic structure has been experimentally determined among a number of magnetic 5d pyrochlore oxides. The Cd 2+ ion is non-magnetic, whereas the Os 5+ ion with a 5d 3 configuration can be magnetic. This compound exhibits a purely electronic continuous metal-insulator transition (MIT) concurrently with a Néel ordering at T MIT ≃ 227 K [2-5]. Magnetic-susceptibility [2, 3] and µSR measurements [6] suggested the Néel ordering, whereas powder neutron diffraction did not confirm the abovementioned observation [7]. Recently, Yamaura et al. have successfully detected a magnetic reflection at the wave vector of q = 0 using resonant X-ray scattering on high-quality single crystals [5]. They showed that only the so-called all-in/all-out magnetic order [see Fig. 1(a)] is compatible with the cubic symmetry of the crystal among the possible q = 0 magnetic orders. The all-in/all-out magnetic ordering has been suggested also in other 5d pyrochlore oxides, i.e, Nd 2 Ir 2 O 7 in experimental work [8] and Y 2 Ir 2 O 7 in theoretical work [9].Despite the recent experimental progress, we are still far from fully understanding the electronic properties of this compound. In particular, several puzzling electronic properties have been reported experimentally: (1) In contrast to the opening of an optical gap of the order of 800 cm −1 (≃ 1100 K) [10], the semiconducting gap continuously vanishes toward low T 's [2,3]. This indicates the absence of a clear charge gap at low T 's which seemingly contradicts the semiconducting behavior of the resistivity up to T MIT . (2) The Néel transition temperature of this compound (= T MIT ) is, to the beset of our knowledge, one of the highest among the magnetic pyrochlore (a) 0.0 0.2 0.4 0.0 0.5 1.0 1.5 2.0 Gap (eV) U eff (eV) (c) 0.0 0.4 0.8 1.2 Os moment (b) NMM AFM AFI FIG. 1: (color online). (a) Cubic unit cell of Cd2Os2O7 contains 8 formula units. Onl...

We study the prototype 5d pyrochlore iridate Y2Ir2O7 from first principles using the local density approximation and dynamical mean-field theory (LDA+DMFT). We map out the phase diagram in the space of temperature, onsite Coulomb repulsion U , and filling. Consistent with experiments, we find that an all-in-all-out ordered insulating phase is stable for realistic values of U . The trigonal crystal field enhances the hybridization between the j eff =1/2 and j eff = 3/2 states, and strong inter-band correlations are induced by the Coulomb interaction, which indicates that a three-band description is important. We demonstrate a substantial band narrowing in the paramagnetic metallic phase and non-Fermi liquid behavior in the electron/hole doped system originating from long-lived quasi-spin moments induced by nearly flat bands.PACS numbers: 71.15. Mb,71.27.+a,71.30.+h The competition and cooperation between spin-orbit coupling (SOC) and electron correlations induces novel phenomena in 4d and 5d transition metal oxides such as spin-orbit-assisted Mott insulators, topological phases, and spin liquids [1]. The pyrochlore iridates A 2 Ir 2 O 7 (A=Pr, Nd, Y, etc.) are an ideal system to study these phenomena because their magnetic and electronic states can be tuned by chemical substitution, pressure, and temperature (T ). Furthermore, intriguing phenomena such as correlated topological phases have been theoretically predicted on their geometrically frustrated crystal structure [1].In 2001, it was reported that these compounds show a crossover from metal to insulator with decreasing A 3+ ionic radii at high T [2] and a magnetic anomaly was found at low T for small A 3+ ionic radii [3]. For the metallic compound A=Pr, experiments revealed spinliquid behavior [4,5] and an unconventional anomalous Hall effect [6]. On the other hand, the Ir magnetic ordering has not been determined for a decade due to the strong neutron absorption by Ir and large magnetic contributions from rare-earth f moments on A 3+ . The magnetic order has only recently been identified as a noncollinear all-in-all-out order [see Fig. 1(a)Among the insulating compounds, Y 2 Ir 2 O 7 has the highest magnetic transition temperature and no f moments. This makes this compound a prototype system for studying strong electron correlations among 5d electrons. A pioneering local density approximation (LDA)+U study for this compound showed that the allin-all-out order is indeed stable at large on-site repulsion U [10]. It also proposed a topological Weyl semimetal as the ground state of some compounds in this series. This stimulated further theoretical studies on the topological nature and unconventional quantum criticality of 5d electrons on the pyrochlore lattice [1,[11][12][13][14][15][16][17][18][19].In pyrochlore iridates, the Ir atoms form a frustrated pyrochlore lattice, a corner-sharing network of tetrahedra [see Fig. 1(a) and Ref. 20]. The so-called j eff =1/2 picture was originally proposed for the insulating quasi-2D compound Sr 2 IrO 4 with the same e...