Effects of Electron-Electron and Electron-Phonon Interactions in Weakly Disordered Conductors and Heterostuctures

We investigate quantum corrections to the conductivity due to the interference of electron-electron (electron-phonon) scattering and elastic electron scattering in weakly disordered conductors. The electron-electron interaction results in a negative $T^2 \ln T$-correction in a 3D conductor. In a quasi-two-dimensional conductor, $d < v_F/T$ ($d$ is the thickness, $v_F$ is the Fermi velocity), with 3D electron spectrum this correction is linear in temperature and differs from that for 2D electrons (G. Zala et. al., Phys. Rev.B {\bf 64}, 214204 (2001)) by a numerical factor. In a quasi-one-dimensional conductor, temperature-dependent correction is proportional to $T^2$. The electron interaction via exchange of virtual phonons also gives $T^2$-correction. The contribution of thermal phonons interacting with electrons via the screened deformation potential results in $T^4$-term and via unscreened deformation potential results in $T^2$-term. The interference contributions dominate over pure electron-phonon scattering in a wide temperature range, which extends with increasing disorder.Comment: 6 pages, 2figure

Quantum interference of electrons in Nb_{5-\delta}Te_4 single crystals

The compound $Nb_{5-\delta}Te_4$ ($\delta=0.23$) with quasi-one-dimensional crystal structure undergoes a transition to superconductivity at $T_c$=0.6--0.9 K. Its electronic transport properties in the normal state are studied in the temperature range 1.3--270 K and in magnetic fields up to 11 T. The temperature variation of the resistivity is weak ($<2$) in the investigated temperature range. Nonmonotonic behavior of the resistivity is observed which is characterized by two local maxima at $T\sim$2 K and $\sim$30 K. The temperature dependence of the resistivity is interpreted as an interplay of weak localization, weak antilocalization, and electron-electron interaction effects in the diffusion and the Cooper channel. The temperature dependence of the dephasing time $\tau_\phi$ extracted from the magnetoresistance data is determined by the electron-phonon interaction. The saturation of $\tau_\phi$ in the low-temperature limit correlates with $T_c$ of the individual crystal and is ascribed to the scattering on magnetic impurities.Comment: 8 pages, 6 figure

Global Food Security Governance: Civil Society Engagement in the Reformed Committee on World Food Security

In 2007/8 world food prices spiked and global economic crisis set in, leaving hundreds of millions of people unable to access adequate food. The international reaction was swift. In a bid for leadership, the 123 member countries of the United Nations’ Committee on World Food Security (CFS) adopted a series of reforms with the aim of becoming the foremost international, inclusive and intergovernmental platform for food security. Central to the reform was the inclusion of participants (including civil society and the private sector) across all activities of the Committee. Drawing on data collected from policy documents, interviews and participant observation, this book examines the re-organization and functioning of a UN Committee that is coming to be known as a best practice in global governance. Framed by key challenges that plague global governance, the impact and implication of increased civil society engagement are examined by tracing policy negotiations within the CFS, in particular, policy roundtables on smallholder sensitive investment and food price volatility and negotiations on the Voluntary Guidelines on the Responsible Governance of Tenure of Land, Fisheries and Forests in the Context of National Food Security, and the Global Strategic Framework for Food Security and Nutrition. The author shows that through their participation in the Committee, civil society actors are influencing policy outcomes. Yet analysis also reveals that the CFS is being undermined by other actors seeking to gain and maintain influence at the global level. By way of this analysis, this book provides empirically-informed insights into increased participation in global governance processes