Saturated simplicial complexes

AbstractAmong shellable complexes a certain class has maximal modular homology, and these are the so-called saturated complexes. We extend the notion of saturation to arbitrary pure complexes and give a survey of their properties. It is shown that saturated complexes can be characterized via the p-rank of incidence matrices and via the structure of links. We show that rank-selected subcomplexes of saturated complexes are also saturated, and that order complexes of geometric lattices are saturated

Determination of the spin-flip time in ferromagnetic SrRuO3 from time-resolved Kerr measurements

We report time-resolved Kerr effect measurements of magnetization dynamics in ferromagnetic SrRuO3. We observe that the demagnetization time slows substantially at temperatures within 15K of the Curie temperature, which is ~ 150K. We analyze the data with a phenomenological model that relates the demagnetization time to the spin flip time. In agreement with our observations the model yields a demagnetization time that is inversely proportional to T-Tc. We also make a direct comparison of the spin flip rate and the Gilbert damping coefficient showing that their ratio very close to kBTc, indicating a common origin for these phenomena

Understanding the nature of electronic effective mass in double-doped SrTiO3_{3}

We present an approach to tune the effective mass in an oxide semiconductor by a double doping mechanism. We demonstrate this in a model oxide system Sr$_{1-x}$La$_x$TiO$_{3-\delta}$, where we can tune the effective mass ranging from 6--20$\mathrm{m_e}$ as a function of filling or carrier concentration and the scattering mechanism, which are dependent on the chosen lanthanum and oxygen vacancy concentrations. The effective mass values were calculated from the Boltzmann transport equation using the measured transport properties of thin films of Sr$_{1-x}$La$_x$TiO$_{3-\delta}$. Our method, which shows that the effective mass decreases with carrier concentration, provides a means for understanding the nature of transport processes in oxides, which typically have large effective mass and low electron mobility, contrary to the tradional high mobility semiconductors.Comment: 5 pages with 4 figure

Electronic properties of buried hetero-interfaces of LaAlO3 on SrTiO3

We have made very thin films of LaAlO3 on TiO2 terminated SrTiO3 and have measured the properties of the resulting interface in various ways. Transport measurements show a maximum sheet carrier density of 1016 cm-2 and a mobility around 104 cm2 V-1 s-1. In situ ultraviolet photoelectron spectroscopy (UPS) indicates that for these samples a finite density of states exists at the Fermi level. From the oxygen pressure dependence measured in both transport as well as the UPS, we detail, as reported previously by us, that oxygen vacancies play an important role in the creation of the charge carriers and that these vacancies are introduced by the pulsed laser deposition process used to make the heterointerfaces. Under the conditions studied the effect of LaAlO3 on the carrier density is found to be minimal.Comment: 19 pages, 6 figure