Linear-T scattering and pairing from antiferromagnetic fluctuations in the (TMTSF)_2X organic superconductors

An exhaustive investigation of metallic electronic transport and superconductivity of organic superconductors (TMTSF)_2PF_6 and (TMTSF)_2ClO_4 in the Pressure-Temperature phase diagram between T=0 and 20 K and a theoretical description based on the weak coupling renormalization group method are reported. The analysis of the data reveals a high temperature domain (T\approx 20 K) in which a regular T^2 electron-electron Umklapp scattering obeys a Kadowaki-Woods law and a low temperature regime (T< 8 K) where the resistivity is dominated by a linear-in temperature component. In both compounds a correlated behavior exists between the linear transport and the extra nuclear spin-lattice relaxation due to antiferromagnetic fluctuations. In addition, a tight connection is clearly established between linear transport and T_c. We propose a theoretical description of the anomalous resistivity based on a weak coupling renormalization group determination of electron-electron scattering rate. A linear resistivity is found and its origin lies in antiferromagnetic correlations sustained by Cooper pairing via constructive interference. The decay of the linear resistivity term under pressure is correlated with the strength of antiferromagnetic spin correlations and T_c, along with an unusual build-up of the Fermi liquid scattering. The results capture the key features of the low temperature electrical transport in the Bechgaard salts

Resonant soft x-ray scattering, stripe order, and the electron spectral function in cuprates

We review the current state of efforts to use resonant soft x-ray scattering (RSXS), which is an elastic, momentum-resolved, valence band probe of strongly correlated electron systems, to study stripe-like phenomena in copper-oxide superconductors and related materials. We review the historical progress including RSXS studies of Wigner crystallization in spin ladder materials, stripe order in 214-phase nickelates, 214-phase cuprates, and other systems. One of the major outstanding issues in RSXS concerns its relationship to more established valence band probes, namely angle-resolved photoemission (ARPES) and scanning tunneling microscopy (STM). These techniques are widely understood as measuring a one-electron spectral function, yet a relationship between RSXS and a spectral function has so far been unclear. Using physical arguments that apply at the oxygen $K$ edge, we show that RSXS measures the square modulus of an advanced version of the Green's function measured with STM. This indicates that, despite being a momentum space probe, RSXS is more closely related to STM than to ARPES techniques. Finally, we close with some discussion of the most promising future directions for RSXS. We will argue that the most promising area lies in high magnetic field studies, particularly of edge states in strongly correlated heterostructures, and the vortex state in superconducting cuprates, where RSXS may clarify the anomalous periodicities observed in recent quantum oscillation experiments.Comment: 15 pages, 1 figure, submitted to special issue of Physica C, "Stripes and Electronic Liquid Crystals in Strongly Correlated Systems.

Organic Superconductors: when correlations and magnetism walk in

This survey provides a brief account for the start of organic superconductivity motivated by the quest for high Tc superconductors and its development since the eighties'. Besides superconductivity found in 1D organics in 1980, progresses in this field of research have contributed to better understand the physics of low dimensional conductors highlighted by the wealth of new remarkable properties. Correlations conspire to govern the low temperature properties of the metallic phase. The contribution of antiferromagnetic fluctuations to the interchain Cooper pairing proposed by the theory is borne out by experimental investigations and supports supercondutivity emerging from a non Fermi liquid background. Quasi one dimensional organic superconductors can therefore be considered as simple prototype systems for the more complex high Tc materials.Comment: 41 pages, 21 figures to be published in Journal of Superconductivity and Novel Magnetis

A Simple Search and Bargaining Model of Real Estate Markets

This paper examines the impact of brokers on buyers' and sellers' search behavior and on the transaction prices in real estate markets. It is shown that the seller and the buyer search less intensively if the house is listed with a broker. The seller gets a higher price when he employs a broker, but the increase in price is smaller than the commission fee. More specifically, the portion of the commission covered by the increase in price is directly related to the bargaining powers of the buyer and the seller. In the special case where the price is determined according to the Nash bargaining solution, the increase in price is shown to be half of the commission fee. It is also shown that an increase in the commission rate increases the equilibrium price but decreases the equilibrium search intensities. Copyright American Real Estate and Urban Economics Association.

Chicago's Office Market: Price Indices, Location and Time

Conventional wisdom holds that overbuilding and high vacancy, coupled with curtailed tax benefits, have led to reduced office property values since the late 1980s. Yet assertions that office real estate values fell between the mid-1980s and mid-1990s are not supported everywhere by convincing evidence. This study offers a hedonic analysis of Chicago area office properties that sold from 1986 through 1993. Whereas earlier office market studies generally have been based on rents, this study focuses on variation in actual sale prices (although the prices were not adjusted for financing differences). The transaction-based index estimated here does not support the existence of a nominal office property price level decline beginning in the mid-to-late 1980s. In fact, the results show an upward trend in office property values after 1986, with nominal declines in office market price levels occurring only in the latter portion of the study period. Copyright American Real Estate and Urban Economics Association.

Music in the exercise domain: A review and synthesis (Part I)

This article is made available through the Brunel Open Access Publishing Fund and can be accessed from the links below - Copyright @ 2012 Taylor & Francis.Since a 1997 review (Karageorghis & Terry) which highlighted the state of knowledge and methodological weaknesses, the number of studies investigating musical reactivity in relation exercise has swelled considerably. In this two-part review paper, the development of conceptual approaches and mechanisms underlying the effects of music are explicated (Part I), followed by a critical review and synthesis of empirical work (spread over Parts I and II). Pre-task music has been shown to optimise arousal, facilitate task-relevant imagery, and improve performance in simple motoric tasks. During repetitive, endurance-type activities, self-selected, motivational, and stimulative music has been shown to enhance affect, reduce ratings of perceived exertion, improve energy efficiency, and lead to increased work output. There is some evidence to suggest that carefully-selected music can promote ergogenic and psychological benefits during high intensity exercise, although it appears to be ineffective in reducing perceptions of exertion beyond the anaerobic threshold. The effects of music appear to be at their most potent when it is used to accompany self-paced exercise or in externally valid conditions. When selected according to its motivational qualities the positive impact of music on both psychological state and performance is magnified. Guidelines are provided for future research and exercise practitioners