Elusive electron-phonon coupling in quantitative analyses of the spectral function

We examine multiple techniques for extracting information from angle-resolved photoemission spectroscopy (ARPES) data, and test them against simulated spectral functions for electron-phonon coupling. We find that, in the low-coupling regime, it is possible to extract self-energy and bare-band parameters through a self-consistent Kramers-Kronig bare-band fitting routine. We also show that the effective coupling parameters deduced from the renormalization of quasiparticle mass, velocity, and spectral weight are momentum dependent and, in general, distinct from the true microscopic coupling; the latter is thus not readily accessible in the quasiparticle dispersion revealed by ARPES.Comment: A high-resolution version can be found at http://www.physics.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Articles/KKBF.pd

A spectral function tour of electron-phonon coupling outside the Migdal limit

We simulate spectral functions for electron-phonon coupling in a filled band system - far from the asymptotic limit often assumed where the phonon energy is very small compared to the Fermi energy in a parabolic band and the Migdal theorem predicting 1+lambda quasiparticle renormalizations is valid. These spectral functions are examined over a wide range of parameter space through techniques often used in angle-resolved photoemission spectroscopy (ARPES). Analyzing over 1200 simulations we consider variations of the microscopic coupling strength, phonon energy and dimensionality for two models: a momentum-independent Holstein model, and momentum-dependent coupling to a breathing mode phonon. In this limit we find that any `effective coupling', lambda_eff, inferred from the quasiparticle renormalizations differs from the microscopic dimensionless coupling characterizing these Hamiltonians, lambda, and could drastically either over- or under-estimate it depending on the particular parameters and model. In contrast, we show that perturbation theory retains good predictive power for low coupling and small momenta, and that the momentum-dependence of the self-energy can be revealed via the relationship between velocity renormalization and quasiparticle strength. Additionally we find that (although not strictly valid) it is often possible to infer the self-energy and bare electronic structure through a self-consistent Kramers-Kronig bare-band fitting; and also that through lineshape alone, when Lorentzian, it is possible to reliably extract the shape of the imaginary part of a momentum-dependent self-energy without reference to the bare-band.Comment: 15 pages, 11 figures. High resolution available here: http://www.physics.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Articles/sf_tour.pd

Endovascular Treatment of a Right-Sided Ureteroiliac Fistula in a Patient with a Simultaneous Left-Sided Ureteroileal Fistula

We describe an 80-year-old female with a left ureteroileal fistula and simultaneously a right ureteroiliac fistula. Her history highlights the predisposing factors of radiation, major surgery in the region, and presence of bilateral double-J-stents. She was successfully treated with an endovascular approach after being initially misdiagnosed. There seems to be an increase in reporting ureteral fistulas, however this entity remains a rare clinical condition that can lead to life-threatening situations. A fast and accurate diagnosis of an ureteroarterial fistula remains a challenge

Synchronous Laparoscopic Radical Nephrectomy Left and Contralateral Right Hemicolectomy during the Same Endoscopic Procedure

Synchronous renal cell carcinoma in patients with colorectal carcinoma is reported in various percentages ranging from 0.03 up to 4.85% (Halak et al. (2000), Capra et al. (2003)). When surgical treatment is indicated usually two separate operations are planned for resection. In open surgery, in such cases simultaneous resection is recommended if possible. Few reports have described the resection of colorectal and renal cell carcinoma in a single laparoscopic procedure. We have shown that combining left radical nephrectomy and right hemicolectomy is technically feasible, safe and that overall operative time can be limited. In our case operative time was 210 minutes, blood loss 100 milliliters, and duration of hospital stay was 8 days. Adequate port placement, preoperative scheduling, and surgical experience are essential to achieve this goal

Determining the Surface-To-Bulk Progression in the Normal-State Electronic Structure of Sr2RuO4 by Angle-Resolved Photoemission and Density Functional Theory

In search of the potential realization of novel normal-state phases on the surface of Sr2RuO4 - those stemming from either topological bulk properties or the interplay between spin-orbit coupling (SO) and the broken symmetry of the surface - we revisit the electronic structure of the top-most layers by ARPES with improved data quality as well as ab-initio LDA slab calculations. We find that the current model of a single surface layer (\surd2x\surd2)R45{\deg} reconstruction does not explain all detected features. The observed depth-dependent signal degradation, together with the close quantitative agreement with LDA+SO slab calculations based on the LEED-determined surface crystal structure, reveal that (at a minimum) the sub-surface layer also undergoes a similar although weaker reconstruction. This points to a surface-to-bulk progression of the electronic states driven by structural instabilities, with no evidence for Dirac and Rashba-type states or surface magnetism.Comment: 4 pages, 4 figures, 1 table. Further information and PDF available at: http://www.phas.ubc.ca/~quantmat/ARPES/PUBLICATIONS/articles.htm

Self-organization of linear nanochannel networks

A theoretical study has been conducted to explore the mechanics of self-organizing channel networks with dimensions in the submicron range and nanorange. The channels form by the partial release and bond back of prestressed thin films. In the release phase, the film spontaneously buckles into wrinkles of a certain wavelength, followed by a bond-back phase in which the final channel geometry is established through cohesive interface attractions. Results are presented in terms of the channel spacing, height, and width as a function of the film stiffness, thickness, eigenstrain, etch width, and interface energy. We have identified two dimensionless parameters that fully quantify the network assembly, showing excellent agreement with experiments. Our results provide valuable insight for the design of submicron and nanoscale channel networks with specific geometries