Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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Access Right: Open AccessInstitution Author: search.filters.institutionAuthor.Çakır, Özgür

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  • Article
    Citation - WoS: 5
    Citation - Scopus: 4
    Electromagnetically Induced Transparency and Absorption Cross-Over With a Four-Level Rydberg System
    (IOP Publishing, 2022) Oyun, Yağız; Çakır, Özgür; Sevinçli, Sevilay
    Electromagnetically induced transparency (EIT) and absorption (EIA) are quantum coherence phenomena which result from the interference of excitation pathways. Combining these with Rydberg atoms have opened up many possibilities for various applications. We introduce a theoretical model to study Rydberg-EIT and Rydberg-EIA effects in cold Cs and Rb atomic ensembles in a four-level ladder type scheme taking into account van der Waals type interactions between the atoms. The proposed many-body method for analysis of such systems involves a self-consistent mean field approach and it produces results which display a very good agreement with recent experiments. Our calculations also successfully demonstrate experimentally observed EIT-EIA cross-over in the Rb case. Being able to simulate the interaction effects in such systems has significant importance, especially for controlling the optical response of these.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Enhanced Indirect Exchange Interactions in the Presence of Circular Potentials in Graphene
    (American Physical Society, 2019) Canbolat, Ahmet Utku; Çakır, Özgür
    We calculate indirect exchange interaction between two magnetic impurities in pristine graphene in the presence of a circular potential. In bulk graphene structures indirect exchange interaction, also known as RKKY (Ruderman-Kittel-Kasuya-Yosida) interaction, shows a power-law decay with distance for both doped and undoped cases. Here we show that under a circular electric potential quasibound states lead to enhanced RKKY interactions between magnetic moments located in the vicinity of the potential well. It is shown that the strength of the potential well and Fermi energy can be tuned to create enhanced, nondecaying, long ranged RKKY interactions. We show that when the Fermi level lies at the quasibound state energy, the scattering processes between the states of the same chirality dominate over the other scattering channels and this leads to a predominantly ferromagnetic, nondecaying interaction between the impurities at long distances. The predicted effect can enable electrical control of RKKY interactions in graphene or other two-dimensional materials.