Linear Response Theory and Optical Conductivity of Floquet Topological Insulators

Motivated by the quest for experimentally accessible dynamical probes of Floquet topological insulators, we formulate the linear response theory of a periodically driven system. We illustrate the applications of this formalism by giving general expressions for optical conductivity of Floquet systems, including its homodyne and heterodyne components and beyond. We obtain the Floquet optical conductivity of specific driven models, including two-dimensional Dirac material such as the surface of a topological insulator, graphene, and the Haldane model irradiated with circularly or linearly polarized laser, as well as semiconductor quantum well driven by an ac potential. We obtain approximate analytical expressions and perform numerically exact calculations of the Floquet optical conductivity in different scenarios of the occupation of the Floquet bands, in particular, the diagonal Floquet distribution and the distribution obtained after a quench. We comment on experimental signatures and detection of Floquet topological phases using optical probes.Comment: 16 pages, 10 figure

Floquet Perturbation Theory: Formalism and Application to Low-Frequency Limit

We develop a low-frequency perturbation theory in the extended Floquet Hilbert space of a periodically driven quantum systems, which puts the high- and low-frequency approximations to the Floquet theory on the same footing. It captures adiabatic perturbation theories recently discussed in the literature as well as diabatic deviation due to Floquet resonances. For illustration, we apply our Floquet perturbation theory to a driven two-level system as in the Schwinger-Rabi and the Landau-Zener-St\"uckelberg-Majorana models. We reproduce some known expressions for transition probabilities in a simple and systematic way and clarify and extend their regime of applicability. We then apply the theory to a periodically-driven system of fermions on the lattice and obtain the spectral properties and the low-frequency dynamics of the system.Comment: v2: 28 single-column pages, 5 figures; various typos fixed; some notation and connection to other perturbation schemes clarified; new, more descriptive title and abstract. Published versio

Quantum noise detects Floquet topological phases

We study quantum noise in a nonequilibrium, periodically driven, open system attached to static leads. Using a Floquet Green's function formalism we show, both analytically and numerically, that local voltage noise spectra can detect the rich structure of Floquet topological phases unambiguously. Remarkably, both regular and anomalous Floquet topological bound states can be detected, and distinguished, via peak structures of noise spectra at the edge around zero-, half-, and full-drive-frequency. We also show that the topological features of local noise are robust against moderate disorder. Thus, local noise measurements are sensitive detectors of Floquet topological phases.Comment: 4.5 pages + supplemental material; v2: improved presentation and new and updated reference

Factorial Invariance of Self-efficacy in Physical Health Care Scale for Men and Women University Students

The present study analyses the psychometric properties of the Selfefficacy in Physical Health Care Scale. The overall sample consisted of 2006 subjects: 902 women and 1104 men, with a mean age of 18.53 years (SD= 1.52) and 18.84 years (SD= 1.55) respectively. The Factorial Psychometric analysis showed that a three-factorial structure (nutrition, physical health and hydration) was viable and adequate for both populations (men and woman) according to the established psychometric requirements when the informers are the students themselves. The results showed that factor structure, factor loadings and intercepts of the instrument could be considered invariant across groups; however, there are differences between groups in favor of men for the means of the nutrition and physical health factors

Ultrabiomicroscopic-Histopathologic Correlations in Individuals with Autosomal Dominant Congenital Microcoria: Three-Generation Family Report

Background: Congenital microcoria (CMC) is due to a maldevelopment of the dilator pupillae muscle of the iris, with a pupil diameter of less than 2 mm. It is associated with juvenile open angle glaucoma and myopia. We report on a three-generation Mexican-Mestizo family with CMC. The eldest member’s iris biopsy proved muscle anomalies. Further, we analyzed novel ultrasound biomicroscopy findings in the family members who did not require surgery. Patients and Methods: A 62-year-old woman, her 41-year-old son and her 9-year-old grandson affected with microcoria since birth, documented by clinical examination and ultrasound biomicroscopy. The eldest member underwent phacoemulsification, and a biopsy of the iris and the anterior capsule of the lens was taken. Results: Ultrasound biomicroscopy confirmed the CMC diagnosis showing iris thinning and a pupil diameter of less than 2 mm. Histopathology of the iris showed a significant reduction of smooth muscle cells, but no alterations of the anterior lens capsule. Discussion: Although CMC is a rare disorder, which is due to a maldevelopment of the dilator pupillae muscle of the iris, it could be associated with juvenile open angle glaucoma and myopia; therefore, precise diagnosis is required. Ultrasound biomicroscopy could be a great option to confirm the disorder

The Apical Submembrane Cytoskeleton Participates in the Organization of the Apical Pole in Epithelial Cells

In a previous publication (Rodriguez, M.L., M. Brignoni, and P.J.I. Salas. 1994. J. Cell Sci. 107: 3145–3151), we described the existence of a terminal web-like structure in nonbrush border cells, which comprises a specifically apical cytokeratin, presumably cytokeratin 19. In the present study we confirmed the apical distribution of cytokeratin 19 and expanded that observation to other epithelial cells in tissue culture and in vivo. In tissue culture, subconfluent cell stocks under continuous treatment with two different 21-mer phosphorothioate oligodeoxy nucleotides that targeted cytokeratin 19 mRNA enabled us to obtain confluent monolayers with a partial (40–70%) and transitory reduction in this protein. The expression of other cytoskeletal proteins was undisturbed. This downregulation of cytokeratin 19 resulted in (a) decrease in the number of microvilli; (b) disorganization of the apical (but not lateral or basal) filamentous actin and abnormal apical microtubules; and (c) depletion or redistribution of apical membrane proteins as determined by differential apical–basolateral biotinylation. In fact, a subset of detergent-insoluble proteins was not expressed on the cell surface in cells with lower levels of cytokeratin 19. Apical proteins purified in the detergent phase of Triton X-114 (typically integral membrane proteins) and those differentially extracted in Triton X-100 at 37°C or in n-octyl-β-d-glycoside at 4°C (representative of GPIanchored proteins), appeared partially redistributed to the basolateral domain. A transmembrane apical protein, sucrase isomaltase, was found mispolarized in a subpopulation of the cells treated with antisense oligonucleotides, while the basolateral polarity of Na+– K+ATPase was not affected. Both sucrase isomaltase and alkaline phosphatase (a GPI-anchored protein) appeared partially depolarized in A19 treated CACO-2 monolayers as determined by differential biotinylation, affinity purification, and immunoblot. These results suggest that an apical submembrane cytoskeleton of intermediate filaments is expressed in a number of epithelia, including those without a brush border, although it may not be universal. In addition, these data indicate that this structure is involved in the organization of the apical region of the cytoplasm and the apical membrane

Effect of inhomogeneities and substrate on the dynamics of the metal-insulator transition in VO2 thin films

We study the thermal relaxation dynamics of VO2 films after the ultrafast photoinduced metal-insulator transition for two VO2 film samples grown on Al2O3 and TiO2 substrates. We find two orders of magnitude difference in the recovery time (a few nanoseconds for the VO2/Al2O3 sample versus hundreds of nanoseconds for the VO2/TiO2 sample). We present a theoretical model to take into account the effect of inhomogeneities in the films on the relaxation dynamics. We obtain quantitative results that show how the microstructure of the VO2 film and the thermal conductivity of the interface between the VO2 film and the substrate affect long time-scale recovery dynamics. We also obtain a simple analytic relationship between the recovery time-scale and the film\u27s parameters