Quantum-fluctuation effects in transport properties of superconductors above the paramagnetic limit

We study the transport in ultrathin disordered film near the quantum critical point induced by the Zeeman field. We calculate corrections to the normal state conductivity due to quantum pairing fluctuations. The fluctuation-induced transport is mediated by virtual rather than real quasi-particles. We find that at zero temperature, where the corrections come from purely quantum fluctuations, the Aslamazov-Larkin paraconductivity term, the Maki-Thompson interference contribution and the density of states effects are all of the same order. The total correction leads to the negative magnetoresistance. This result is in qualitative agreement with the recent transport observations in the parallel magnetic field of the homogeneously disordered amorphous films and superconducting two-dimensional electron gas realized at the oxide interfaces.Comment: 4+ pages, 1 figur

Strengthening gold-gold bonds by complexing gold clusters with noble gases

We report an unexpectedly strong and complex chemical bonding of rare-gas atoms to neutral gold clusters. The bonding features are consistently reproduced at different levels of approximation within density-functional theory and beyond: from GGA, through hybrid and double-hybrid functionals, up to renormalized second-order perturbation theory. The main finding is that the adsorption of Ar, Kr, and Xe reduces electron-electron repulsion within gold dimer, causing strengthening of the Au-Au bond. Differently from the dimer, the rare-gas adsorption effects on the gold trimer's geometry and vibrational frequencies are mainly due to electron occupation of the trimer's lowest unoccupied molecular orbital. For the trimer, the theoretical results are also consistent with far-infrared multiple photon dissociation experiments.Comment: To be published in Inorganic Chemistry Communication

Brownian scattering of a spinon in a Luttinger liquid

We consider strongly interacting one-dimensional electron liquids where elementary excitations carry either spin or charge. At small temperatures a spinon created at the bottom of its band scatters off low-energy spin- and charge-excitations and follows the diffusive motion of a Brownian particle in momentum space. We calculate the mobility characterizing these processes, and show that the resulting diffusion coefficient of the spinon is parametrically enhanced at low temperatures compared to that of a mobile impurity in a spinless Luttinger liquid. We briefly discuss that this hints at the relevance of spin in the process of equilibration of strongly interacting one-dimensional electrons, and comment on implications for transport in clean single channel quantum wires

Incoherent pair tunneling in the pseudogap phase of cuprates

Motivated by a recent experiment by Bergeal et al., we reconsider incoherent pair tunneling in a cuprate junction formed from an optimally doped superconducting lead and an underdoped normal metallic lead. We study the impact of the pseudogap on the pair tunneling by describing fermions in the underdoped lead with a model self-energy that has been developed to reproduce photoemission data. We find that the pseudogap causes an additional temperature dependent suppression of the pair contribution to the tunneling current. We discuss consistency with available experimental data and propose future experimental directions.Comment: 5 pages, 3 figure

Magnetic penetration depth in disordered iron-based superconductors

We study the effect of disorder on the London penetration depth in iron-based superconductors. The theory is based on a two-band model with quasi-two-dimensional Fermi surfaces, which allows for the coexistence region in the phase diagram between magnetic and superconducting states in the presence of intraband and interband scattering. Within the quasiclassical approximation we derive and solve Eilenberger's equations, which include a weak external magnetic field, and provide analytical expressions for the penetration depth in the various limiting cases. A complete numerical analysis of the doping and temperature dependence of the London penetration depth reveals the crucial effect of disorder scattering, which is especially pronounced in the coexistence phase. The experimental implications of our results are discussed.Comment: 10 pages, 6 figure