Search for: All records

A<sc>bstract</sc> We study anO(N) invariant surface defect in the Wilson-Fisher conformal field theory (CFT) ind= 4 –ϵdimensions. This defect is defined by mass deformation on a two-dimensional surface that generates localized disorder and is conjectured to factorize into a pair of ordinary boundary conditions ind= 3. We determine defect CFT data associated with the lightestO(N) singlet and vector operators up to the third order in theϵ-expansion, find agreements with results from numerical methods and provide support for the factorization proposal ind= 3. Along the way, we observe surprising non-renormalization properties for surface anomalous dimensions and operator-product-expansion coefficients in theϵ-expansion. We also analyze the full conformal anomalies for the surface defect. 

Photon induced changes in charge distributions and conductivities of oxide nanoparticles (rhodium doped strontium titanate) have been determined using in situ electron holography. The holography-based approach relies on the application of two distinct stimuli to the material of interest: electrons and photons. The high energy electron beam stimulates the formation of a layer of positive surface charge due to secondary electron emission. Light illumination reduces this charge due to enhanced electronic conductivity arising from photo-electron excitation. For moderate photon and electron illumination rates, there is a simple linear relationship between the steady state surface charge and the sample conductivity. For rhodium doped strontium titanate, we observe a factor of 3 increase in the conductivity for the illumination conditions employed here. The approach is general and can be employed to measure photo-induced changes in other semiconducting systems.