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We determine the bounday of the fully polarized ferromagnetic states in the one dimensional Kondo lattice model at partial conduction electron band filling by using a newly developed infinite size DMRG method which conserves the total spin quantum numbers. The obtained paramagnetic to ferromagnetic phase bounday is bellow J ≍ 3.5 for the whole range of band filling. By this we solve the controversy in the phase diagram over the extent of the ferromagnetic region close to half filling. [ABSTRACT FROM AUTHOR]

We report studies of the dependence of the open-circuit voltage (VOC) of polymer/titanium dioxide hybrid devices on the ionization potential of the polymer (IP). Once corrected for differences in photocarrier generation by the polymers, the measured VOC values vary linearly with the polymer IP, with a slope of 0.8±0.1. This behavior agrees with recent studies of polymer/fullerene photovoltaic devices and is consistent with the hypothesis that VOC of an organic donor-acceptor solar cell is limited by the energy difference between the highest occupied molecular orbital of the donor (in this case, the polymer) and the lowest unoccupied electronic level of the acceptor (in this case, the conduction band edge of the TiO2). [ABSTRACT FROM AUTHOR]

We report on charge transport in organic field-effect transistors based on poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) as the active polymer layer with saturation field-effect mobilities as large as 1 cm2 V-1 s-1. This is achieved by employing Pt instead of the commonly used Au as the contacting electrode and allows for a significant reduction in the metal/polymer contact resistance. The mobility increases as a function of decreasing channel length, consistent with a Poole-Frenkel model of charge transport, and reaches record mobilities of 1 cm2 V-1 s-1 or more at channel lengths on the order of few microns in an undoped solution-processed polymer cast on an oxide gate dielectric. [ABSTRACT FROM AUTHOR]

We study the quantum critical phase of an SU(2) symmetric spin-2 chain obtained from spin-2 bosons in a one-dimensional lattice. We obtain the scaling of the finite-size energies and entanglement entropy by exact diagonalization and density-matrix renormalization group methods. From the numerical results of the energy spectra, central charge, and scaling dimension we identify the conformal field theory describing the whole critical phase to be the SU(3)1 Wess-Zumino-Witten model. We find that, while the Hamiltonian is only SU(2) invariant, in this critical phase there is an emergent SU(3) symmetry in the thermodynamic limit. [ABSTRACT FROM AUTHOR]

We perform an extensive density-matrix renormalization-group study of the ground-state phase diagram of the spin-1/2 J1-J2 Heisenberg model on the kagome lattice. We focus on the region of the phase diagram around the kagome Heisenberg antiferromagnet, i.e., at J2 = 0. We investigate the static spin structure factor, the magnetic correlation lengths, and the spin gaps. Our results are consistent with the absence of magnetic order in a narrow region around J2 ≈ 0, although strong finite-size effects do not allow us to accurately determine the phase boundaries. This result is in agreement with the presence of an extended spin-liquid region, as it has been proposed recently. Outside the disordered region, we find that for ferromagnetic and antiferromagnetic J2, the ground state displays signatures of the magnetic order of the √3 × √3 and the q = 0 type, respectively. Finally, we focus on the structure of the entanglement spectrum (ES) in the q = 0 ordered phase. We discuss the importance of the choice of the bipartition on the finite-size structure of the ES. [ABSTRACT FROM AUTHOR]

In this paper, we apply the formalism of translation invariant (continuous) matrix product states in the thermodynamic limit to (1 + 1 )-dimensional critical models. Finite bond dimension bounds the entanglement entropy and introduces an effective finite correlation length, so that the state is perturbed away from criticality. The assumption that the scaling hypothesis holds for this kind of perturbation is known in the literature as finite entanglement scaling. We provide further evidence for the validity of finite entanglement scaling and based on this formulate a scaling algorithm to estimate the central charge and critical exponents of the conformally invariant field theories describing the critical models under investigation. The algorithm is applied to three exemplary models; the cMPS version to the nonrelativistic Lieb-Liniger model and the relativistic massless boson, and MPS version to the one-dimensional quantum Ising model at the critical point. Another new aspect to our approach is that we directly use the (c)MPS induced correlation length rather than the bond dimension as scaling parameter. This choice is motivated by several theoretical arguments as well as by the remarkable accuracy of our results. [ABSTRACT FROM AUTHOR]

We report the discovery of a correlated insulator with a bulk gap at 2/3 filling in a geometrically frustrated Hubbard model that describes the low-energy physics of Mo3S7(dmit)3. This is very different from the Mott insulator expected at half-filling. We show that the insulating phase, which persists even for very weak electron-electron interactions (U), is adiabatically connected to the Haldane phase and is consistent with experiments on Mo3S7(dmit)3. [ABSTRACT FROM AUTHOR]

In magnetically ordered systems, the breaking of SU(2) symmetry in the thermodynamic limit is associated with the appearance of a special type of low-lying excitations in finite-size energy spectra, the so-called tower of states (TOS). In the present work, we numerically demonstrate that there is a correspondence between the SU(2) tower of states and the lower part of the ground-state entanglement spectrum (ES). Using state-of-the-art density matrix renormalization group (DMRG) calculations, we examine the ES of the 2D antiferromagnetic J1-J2 Heisenberg model on both the triangular and kagome lattice. At large ferromagnetic J2, the model exhibits a magnetically ordered ground state. Correspondingly, its ES contains a family of low-lying levels that are reminiscent of the energy tower of states. Their behavior (level counting, finite-size scaling in the thermodynamic limit) sharply reflects TOS features, and is characterized in terms of an effective entanglement Hamiltonian that we provide. At large system sizes, TOS levels are divided from the rest by an entanglement gap. Our analysis suggests that (TOS) entanglement spectroscopy provides an alternative tool for detecting and characterizing SU(2)-broken phases using DMRG. [ABSTRACT FROM AUTHOR]

We report on charge transport in organic field-effect transistors based on poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) as the active polymer layer with saturation field-effect mobilities as large as 1 cm2 V-1 s-1. This is achieved by employing Pt instead of the commonly used Au as the contacting electrode and allows for a significant reduction in the metal/polymer contact resistance. The mobility increases as a function of decreasing channel length, consistent with a Poole-Frenkel model of charge transport, and reaches record mobilities of 1 cm2 V-1 s-1 or more at channel lengths on the order of few microns in an undoped solution-processed polymer cast on an oxide gate dielectric. [ABSTRACT FROM AUTHOR]