Frequency-dependent constraints on cosmic birefringence from the LFI and HFI Planck Data Release 4

We present new constraints on the frequency dependence of the cosmic birefringence angle from the Planck Data Release 4 polarization maps. An axion field coupled to electromagnetism predicts a nearly frequency-independent birefringence angle, β ν  =  β , while Faraday rotation from local magnetic fields and Lorentz violating theories predict a cosmic birefringence angle that is proportional to the frequency, ν , to the power of some integer n , β ν  ∝  ν n . In this work, we first sampled β ν individually for each polarized HFI frequency band in addition to the 70 GHz channel from the LFI. We also constrained a power law formula for the birefringence angle, β ν  =  β 0 ( ν / ν 0 ) n , with ν 0  = 150 GHz. For a nearly full-sky measurement, f sky  = 0.93, we find β 0  = 0.26° ±0.11° (68% C.L.) and n  = −0.45 −0.82 +0.61 when we ignore the intrinsic EB correlations of the polarized foreground emission, and β 0  = 0.33° ±0.12° and n  = −0.37 −0.64 +0.49 when we use a filamentary dust model for the foreground EB . Next, we used all the polarized Planck maps, including the 30 and 44 GHz frequency bands. These bands have a negligible foreground contribution from polarized dust emission and we thus treated them separately. Without any modeling of the intrinsic EB of the foreground, we generally find that the inclusion of the 30 and 44 GHz frequency bands raises the measured values of β ν and tightens n . At nearly full-sky, we measure β 0  = 0.29° −0.11° +0.10° and n  = −0.35 −0.47 +0.48 . Assuming no frequency dependence, we measure β  = 0.33° ±0.10°. If our measurements have effectively mitigated the EB of the foreground, our constraints are consistent with a mostly frequency-independent signal of cosmic birefringence

Triplet Proximity Effect in Heterostructures with Spin-Orbit Coupling and Precessing Magnetic Fields

Vi vil bruke den kvasiklassiske teorien om superledere i det diffuse grensesjiktet for å gjennomføre to forskjellige forskningsprosjekt. Det første prosjektet ser på et sidestilt Josephson-kobling med iboende, Rashba-type spinn-bane kobling som vi viser kan bære en langt-rekkende superstrøm i en sterkt polarisert ferromagnet. Dette oppsettet har fokusert på å være eksperimentelt gjennomførbart, og bare en rotasjon av magnetfeltet i planet trengs for å effektivt skru av den langt-trekkende superstrømmen. For noen parametere kan rotasjonen i planet også forårsake en 0-pi-transisjon som betyr at det finnes en vinkel i planet hvor strømmen er null. Det neste prosjektet ser på heterostrukturerer hvor en ferromagnet har et preseserende magnetfelt. Disse systemene er drevet ut av likevekt, og vi har laget et rammeverk for å regne ut observabler ved å finne Greens-funksjoner og fordelingsfunksjoner i en ramme der det magnetiske feltet er stasjonært. Med dette rammeverket viser vi hvordan superledende orden endrer resultatet sammenlignet med et preseserende magnetfelt i en ferromagnet i nærheten av bare metaller i normal tilstand. Vi viser også at en Josephson-kobling med en presesjon og makroskopisk faseforskjell ulik null kan erfare en ladningsakkumulering som driver en resistiv strøm. Den resistive strømmen kan bli stilt inn av den angulære frekvensen til magnetfeltet, og det kan finnes en frekvens hvor ladningsakkumuleringen er null. Denne ladningsakkumuleringen finnes også sted i superlederne som induserer en spenningsforskjell over koblingen. Vi konkluderer derfor at faseforskjellen vil endre seg over tid på grunn av denne spenningsforskjellen

Long-ranged triplet supercurrent in a single in-plane ferromagnet with spin-orbit coupled contacts to superconductors

By converting conventional spin-singlet Cooper pairs to polarized spin-triplet pairs, it is possible to sustain long-ranged spin-polarized supercurrents flowing through strong ferromagnets. Obtaining such a conversion via spin-orbit interactions, rather than magnetic inhomogeneities, has recently been explored in the literature. A challenging aspect with regard to experimental detection has been that in order for Rashba spin-orbit interactions, present, e.g., at interfaces due to inversion symmetry breaking, to generate such long-ranged supercurrents, an out-of-plane component of the magnetization is required. This limits the choice of materials and can induce vortices in the superconducting region complicating the interpretation of measurements. Therefore, it would be desirable to identify a way in which Rashba spin-orbit interactions can induce long-ranged supercurrents for purely in-plane rotations of the magnetization. Here, we show that this is possible in a lateral Josephson junction where two superconducting electrodes are placed in contact with a ferromagnetic film via two thin, heavy normal metals. The magnitude of the supercurrent in such a setup becomes tunable by the in-plane magnetization angle when using only a single magnetic layer. These results could provide a new and simpler way to generate controllable spin-polarized supercurrents than previous experiments which utilized complicated magnetically textured Josephson junctions