2s exciton-polariton revealed in an external magnetic field

We demonstrate the existence of the excited state of an exciton-polariton in a semiconductor microcavity. The strong coupling of the quantum well heavy-hole exciton in an excited 2s state to the cavity photon is observed in non-zero magnetic field due to surprisingly fast increase of Rabi energy of the 2s exciton-polariton in magnetic field. This effect is explained by a strong modification of the wave-function of the relative electron-hole motion for the 2s exciton state.Comment: 5 pages, 5 figure

Spin polarization of exciton-polariton condensate in a photonic synthetic effective magnetic field

We investigate the spin polarization of localized exciton-polariton condensates. We demonstrate the presence of an effective magnetic field leading to the formation of elliptically polarized condensates. We show that this synthetic field has an entirely photonic origin, which we believe is unique for the CdTe-based microcavities. Moreover, the degree of spin polarization of localized polariton condensates in samples with magnetic ions depends on the excitation power or polarization of the non-resonant excitation laser. In an external magnetic field, the semimagnetic condensate spontaneously builds up strong spin polarization. Based on the magnetic field behavior of the condensate in the presence of magnetic ions, we apply a model that allows us to estimate the polariton-polariton interaction strength in a CdTe-system to approx. 0.8 $\mu \text{eV}\!\cdot\!\mu \text{m}^2$

Angular dependence of giant Zeeman effect for semimagnetic cavity polariton

The observation of spin-related phenomena of microcavity polaritons has been limited due to the weak Zeeman effect of nonmagnetic semiconductors. We demonstrate that the incorporation of magnetic ions into quantum wells placed in a nonmagnetic microcavity results in enhanced effects of magnetic field on exciton-polaritons. We show that in such a structure the Zeeman splitting of exciton-polaritons strongly depends on the photon-exciton detuning and polariton wave vector. Our experimental data are explained by a model where the impact of magnetic field on the lower polariton state is directly inherited from the excitonic component, and the coupling strength to the cavity photon is modified by an external magnetic field

Observational Diagnostics of Gas Flows: Insights from Cosmological Simulations

Galactic accretion interacts in complex ways with gaseous halos, including galactic winds. As a result, observational diagnostics typically probe a range of intertwined physical phenomena. Because of this complexity, cosmological hydrodynamic simulations have played a key role in developing observational diagnostics of galactic accretion. In this chapter, we review the status of different observational diagnostics of circumgalactic gas flows, in both absorption (galaxy pair and down-the-barrel observations in neutral hydrogen and metals; kinematic and azimuthal angle diagnostics; the cosmological column density distribution; and metallicity) and emission (Lya; UV metal lines; and diffuse X-rays). We conclude that there is no simple and robust way to identify galactic accretion in individual measurements. Rather, progress in testing galactic accretion models is likely to come from systematic, statistical comparisons of simulation predictions with observations. We discuss specific areas where progress is likely to be particularly fruitful over the next few years.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics and Space Science Library, eds. A. J. Fox & R. Dave, to be published by Springer. Typos correcte

Grey and white matter correlates of recent and remote autobiographical memory retrieval:Insights from the dementias

The capacity to remember self-referential past events relies on the integrity of a distributed neural network. Controversy exists, however, regarding the involvement of specific brain structures for the retrieval of recently experienced versus more distant events. Here, we explored how characteristic patterns of atrophy in neurodegenerative disorders differentially disrupt remote versus recent autobiographical memory. Eleven behavioural-variant frontotemporal dementia, 10 semantic dementia, 15 Alzheimer's disease patients and 14 healthy older Controls completed the Autobiographical Interview. All patient groups displayed significant remote memory impairments relative to Controls. Similarly, recent period retrieval was significantly compromised in behavioural-variant frontotemporal dementia and Alzheimer's disease, yet semantic dementia patients scored in line with Controls. Voxel-based morphometry and diffusion tensor imaging analyses, for all participants combined, were conducted to investigate grey and white matter correlates of remote and recent autobiographical memory retrieval. Neural correlates common to both recent and remote time periods were identified, including the hippocampus, medial prefrontal, and frontopolar cortices, and the forceps minor and left hippocampal portion of the cingulum bundle. Regions exclusively implicated in each time period were also identified. The integrity of the anterior temporal cortices was related to the retrieval of remote memories, whereas the posterior cingulate cortex emerged as a structure significantly associated with recent autobiographical memory retrieval. This study represents the first investigation of the grey and white matter correlates of remote and recent autobiographical memory retrieval in neurodegenerative disorders. Our findings demonstrate the importance of core brain structures, including the medial prefrontal cortex and hippocampus, irrespective of time period, and point towards the contribution of discrete regions in mediating successful retrieval of distant versus recently experienced events