191 research outputs found
Power-Law Decay of Standing Waves on the Surface of Topological Insulators
We propose a general theory on the standing waves (quasiparticle interference
pattern) caused by the scattering of surface states off step edges in
topological insulators, in which the extremal points on the constant energy
contour of surface band play the dominant role. Experimentally we image the
interference patterns on both BiTe and BiSe films by measuring
the local density of states using a scanning tunneling microscope. The observed
decay indices of the standing waves agree excellently with the theoretical
prediction: In BiSe, only a single decay index of -3/2 exists; while in
BiTe with strongly warped surface band, it varies from -3/2 to -1/2 and
finally to -1 as the energy increases. The -1/2 decay indicates that the
suppression of backscattering due to time-reversal symmetry does not
necessarily lead to a spatial decay rate faster than that in the conventional
two-dimensional electron system. Our formalism can also explain the
characteristic scattering wave vectors of the standing wave caused by
non-magnetic impurities on BiTe.Comment: 4 pages, 3 figure
Characteristics of Human Brain Activity during the Evaluation of Service-to-Service Brand Extension
Brand extension is a marketing strategy to apply the previously established brand name into new goods or service. A number of studies have reported the characteristics of human event-related potentials (ERPs) in response to the evaluation of goods-to-goods brand extension. In contrast, human brain responses to the evaluation of service extension are relatively unexplored. The aim of this study was investigating cognitive processes underlying the evaluation of service-to-service brand extension with electroencephalography (EEG). A total of 56 text stimuli composed of service brand name (S1) followed by extended service name (S2) were presented to participants. The EEG of participants was recorded while participants were asked to evaluate whether a given brand extension was acceptable or not. The behavioral results revealed that participants could evaluate brand extension though they had little knowledge about the extended services, indicating the role of brand in the evaluation of the services. Additionally, we developed a method of grouping brand extension stimuli according to the fit levels obtained from behavioral responses, instead of grouping of stimuli a priori. The ERP analysis identified three components during the evaluation of brand extension: N2, P300, and N400. No difference in the N2 amplitude was found among the different levels of a fit between S1 and S2. The P300 amplitude for the low level of fit was greater than those for higher levels (p < 0.05). The N400 amplitude was more negative for the mid- and high-level fits than the low level. The ERP results of P300 and N400 indicate that the early stage of brain extension evaluation might first detect low-fit brand extension as an improbable target followed by the late stage of the integration of S2 into S1. Along with previous findings, our results demonstrate different cognitive evaluation of service-to-service brand extension from goods-to-goods
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