Non-Hermitian invisibility in tight-binding lattices

11 pages, 4 figuresA flexible control of wave scattering in complex media is of relevance in different areas of classical and quantum physics. Recently, a great interest has been devoted to scattering engineering in non-Hermitian systems, with the prediction and demonstration of new classes of non-Hermitian potentials with unique scattering properties, such as transparent and invisibile potentials or one-way reflectionless potentials. Such potentials have been found for both continuous and discrete (lattice) systems. However, wave scattering in lattice systems displays some distinct features arising from the discrete (rather than continuous) translational invariance of the system, characterized by a finite band of allowed energies and a finite speed of wave propagation on the lattice. Such distinct features can be exploited to realize invisibility on a lattice with methods that fail when applied to continuous systems. Here we show that a wide class of time-dependent non-Hermitian scattering potentials or defects with arbitrary spatial shape can be synthesized in an Hermitian single-band tight-binding lattice, which are fully invisible owing to the limited energy bandwidth of the lattice.Peer reviewe

Magneto-optical Kerr effect (MOKE) measurements with uniform laser profiles

The probability distribution of the amplitude DeltaM of Barkhausen jumps during magnetization reversal in thin films can be measured with optical techniques since each jump produces a variation DeltaI of the laser beam intensity used to probe magnetization. Here we present a theoretical model which demonstrates that no distortion takes place if P(DeltaM) is a power law P(DeltaM)=DeltaM^(-alpha) with alpha >= 1.0. This prediction has been experimentally confirmed by measuring P(DeltaI) in the same experimental conditions but in two different ways: first with a Gaussian and then with a constant intensity laser profile. In both cases the same power-law distribution has been observed with alpha=1

The MariX source (Multidisciplinary Advanced Research Infrastructure with X-rays)

MariX (Multidisciplinary advanced research infra-structure with X-rays) is a joint project of INFN and University of Milan, aiming at developing a twin X-ray Source of advanced characteristics for the future Sci-entific Campus of the University of Milan. Presently in its design study phase, it will be built in the post Expo area located in north-west Milan district. The first component of the X-source MariX is BriXS (Bright and compact X-ray Source), a Compton X-ray source based on superconducting cavities technology for the electron beam with energy recirculation and on a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz, producing 20-180 keV radiation for medical applications. The BriXS accelerator is also serving as injector of a 3.8 GeV superconductive linac, driving a X-ray FEL at 1 MHz, for providing coherent, moderate flux radiation at 0.3-10 KeV at 1 MHz. Scientific case, layout and typical parameters of MariX will be discussed