Phenomenological model for charge dynamics and optical response of disordered systems: application to organic semiconductors

We provide a phenomenological formula which describes the low-frequency optical absorption of charge carriers in disordered systems with localization. This allows to extract, from experimental data on the optical conductivity, the relevant microscopic parameters determining the transport properties, such as the carrier localization length and the elastic and inelastic scattering times. This general formula is tested and applied here to organic semiconductors, where dynamical molecular disorder is known to play a key role in the transport properties. The present treatment captures the basic ideas underlying the recently proposed transient localization scenario for charge transport, extending it from the d.c. mobility to the frequency domain. When applied to existing optical measurements in rubrene FETs, our analysis provides quantitative evidence for the transient localization phenomenon. Possible applications to other disordered electronic systems are briefly discussed.Comment: extended version with optical conductivity formulas for both non-degenerate and degenerate electron system

Avoiding Stripe Order: Emergence of the Supercooled Electron Liquid

In the absence of disorder, electrons can display glassy behavior through supercooling the liquid state, avoiding the solidification into a charge ordered state. Such supercooled electron liquids are experimentally found in organic $\theta$-$MM'$ compounds. We present theoretical results that qualitatively capture the experimental findings. At intermediate temperatures, the conducting state crosses over into a weakly insulating pseudogap phase. The stripe order phase transition is first order, so that the liquid phase is metastable below $T_s$. In the supercooled liquid phase the resistivity increases further and the density of states at the Fermi level is suppressed, indicating kinetic arrest and the formation of a glassy state. Our results are obtained using classical Extended Dynamical Mean Field Theory.Comment: 4 pages, 4 figures, submitted to the proceedings of "Superstripes 2015", Journal of Superconductivity and Novel Magnetism (2015

Strange metal behavior from incoherent carriers scattered by local moments

We study metallic transport in an effective model that describes the coupling of electrons to fluctuating magnetic moments with full SU(2) symmetry, exhibiting characteristic behavior of metals at the approach of the Mott transition. We show that scattering by fluctuating local moments causes a fully incoherent regime of electron transport with linear T-dependent resistivities. This strange metal regime is characterized by almost universal, "Planckian" slope and a finite intercept at $T=0$, that we can associate respectively to the fluctuations in orientation and amplitude of the local moments. Our results indicate a route for understanding the microscopic origin of strange metal behavior that is unrelated to quantum criticality and does not rely on the existence of quasiparticles.Comment: 5 pages, 3 figure

Glassy dynamics in geometrically frustrated Coulomb liquids without disorder

We show that introducing long-range Coulomb interactions immediately lifts the massive ground state degeneracy induced by geometric frustration for electrons on quarter-filled triangular lattices in the classical limit. Important consequences include the stabilization of a stripe-ordered crystalline (global) ground state, but also the emergence of very many low-lying metastable states with amorphous "stripe-glass" spatial structures. Melting of the stripe order thus leads to a frustrated Coulomb liquid at intermediate temperatures, showing remarkably slow (viscous) dynamics, with very long relaxation times growing in Arrhenius fashion upon cooling, as typical of strong glass formers. On shorter time scales, the system falls out of equilibrium and displays the aging phenomena characteristic of supercooled liquids above the glass transition. Our results show remarkable similarity with the recent observations of charge-glass behavior in ultra-clean triangular organic materials of the $\theta$-(BEDT-TTF)$_2$ family.Comment: 5 pages,4 figure

Impact of quantized vibrations on the efficiency of interfacial charge separation in photovoltaic devices

We demonstrate that charge separation at donor-acceptor interfaces is a complex process that is controlled by the combined action of Coulomb binding for electron-hole pairs and partial relaxation due to quantized phonons. A joint electron-vibration quantum dynamical study reveals that high energy vibrations sensitively tune the charge transfer probability as a function of time and injection energy, due to polaron formation. These results have bearings for the optimization of energy transfer both in organic and quantum dot photovoltaics, as well as in biological light harvesting complexes.Comment: 5 pages, 3 figures. v2 contains additional discussion of experiments, and extra physical motivatio

Emergent heavy fermion behavior at the Wigner-Mott transition

We study charge ordering driven by Coulomb interactions on triangular lattices relevant to the Wigner-Mott transition in two dimensions. Dynamical mean-field theory reveals the pinball liquid phase, a charge ordered metallic phase containing quasilocalized (pins) coexisting with itinerant (balls) electrons. Based on an effective periodic Anderson model for this phase, we find an antiferromagnetic Kondo coupling between pins and balls and strong quasiparticle renormalization. Non-Fermi liquid behavior can occur in such charge ordered systems due to the spin-flip scattering of itinerant electrons off the pins in analogy with heavy fermion compoundsJ. M. acknowledges financial support from MINECO (MAT2012-37263-C02-01). This work is supported by the French National Research Agency through Grant No. ANR-12-JS04-0003-01 SUBRISSYM

Pinball liquid phase from Hund's coupling in frustrated transition metal oxides

The interplay of non-local Coulomb repulsion and Hund's coupling in the d-orbital manifold in frustrated triangular lattices is analyzed by a mutliband extended Hubbard model. We find a rich phase diagram with several competing phases, including a robust pinball liquid phase, which is an unconventional metal characterized by threefold charge order, bad metallic behavior and the emergence of high spin local moments. Our results naturally explain the anomalous charge-ordered metallic state observed in the triangular layered compound AgNiO2. The potential relevance to other triangular transition metal oxides is discussed.Comment: 4 pages, 4 figure

Pseudogap metal induced by long-range Coulomb interactions

In correlated electron systems the metallic character of a material can be strongly suppressed near an integer concentration of conduction electrons as Coulomb interactions forbid the double occupancy of local atomic orbitals. While the Mott-Hubbard physics arising from such on-site interactions has been largely studied, several unexplained phenomena observed in correlated materials challenge this description and call for the development of new ideas. Here we explore a general route for obtaining correlated behavior that is decidedly different from the Mott-Hubbard mechanism and instead relies on the presence of unscreened, long-range Coulomb interactions. We find a previously unreported pseudogap metal phase characterized by a divergent quasiparticle mass and the opening of a Coulomb pseudogap in the electronic spectrum. The destruction of the Fermi liquid state occurs because the electrons move in a nearly frozen, disordered charge background, as collective charge rearrangements are drastically slowed down by the frustrating nature of long-range potentials on discrete lattices. The present pseudogap metal realizes an early conjecture by Efros, that a soft Coulomb gap should appear for quantum lattice electrons with strong unscreened interactions due to self-generated randomness.Comment: 4 pages + 3 pages supplementary informatio

Royal Jelly: An ancient remedy with remarkable antibacterial properties

Royal Jelly (RJ), a honeybee hypopharyngeal gland secretion of young nurse and an exclusive nourishment for bee queen, has been used since ancient times for care and human health and it is still very important in traditional and folkloristic medicine, especially in Asia within the apitherapy. Recently, RJ and its protein and lipid components have been subjected to several investigations on their antimicrobial activity due to extensive traditional uses and for a future application in medicine. Antimicrobial activities of crude Royal Jelly, Royalisin, 10-hydroxy-2-decenoic acid, Jelleines, Major Royal Jelly Proteins against different bacteria have been reported. All these beehive products showed antimicrobial activities that lead their potential employment in several fields as natural additives. RJ and its derived compounds show a highest activity especially against Gram positive bacteria. The purpose of this Review is to summarize the results of antimicrobial studies of Royal Jelly following the timescale of the researches. From the first scientific applications to the isolation of the single components in order to better understand its application in the past years and propose an employment in future studies as a natural antimicrobial agent

Identify the type of pleural effusion with lung ultrasound: a case report and State-of-Art

Pleural effusion is the most common pleural pathology and is seen in a large group of patients admitted to internal medicine wards.The purpose of this state of art literature review is to describe the various ultrasound findings that can be observed, to highlight the ability of lung ultrasound to facilitate differential diagnosis by pointing to a specific type of effusion and its cause.To this end, the clinical case description aims to demonstrate the above and promote the use of bedside lung ultrasound by considering this technique as the fifth physical examination technique after inspection, palpation, percussion and auscultation