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Using Floquet-theory, it is shown that the asymmetric monolayer graphene exhibit a novel nonlinear incoherent optical phenomenon under applied intense pump field. Rabi oscillations in graphene are predicted to exhibit anomalous behavior in off-resonance. In this paper, a systematic study is done to observe these oscillations in an experimentally processed material by calculating the differential transmission coefficient using the pump-probe technique. The effect of pump duration on the differential transmission coefficient is also determined. [ABSTRACT FROM AUTHOR]

In this paper, we report the optical characteristics such as optical band gap, absorption edge, and photoluminescence (PL) spectra of PVA (polyvinyl alcohol)-GO (graphene oxide) nanocomposites in form of free standing thin film which are prepared by simple solution mixing method. In addition, we have also determined the FTIR (Fourier-transform infrared spectroscopy) spectra in order to confirm presence of the functional group and their vibrational modes. [ABSTRACT FROM AUTHOR]

The structural and emission analysis of Sr2SnO4, Sr1.99Eu0.01SnO4, and Sr2Sn0.99Eu0.01O4 were analysed in detail. The thermal analysis of the mixture of raw materials reveals the reaction among the raw materials takes place around 1000°C. The Reitveld refinement of the x-ray diffraction data shows the solubility of Eu on both site of Sr2SnO4. Higher crystallite size and lattice strain were observed for Sr1.99Eu0.01SnO4 than Sr2Sn0.99Eu0.01O4, because Eu3+ acts as donor at Sr2+ site while as acceptor at Sn4+ site. Absences of any band associated with raw materials in Raman spectrum also confirm the monophasic nature of the sample. The photoluminescence (PL) spectra of Eu-doped samples exhibits strong peak at 612 nm ascribed to electric dipole transition 5D0→7F2 of Eu3+ shows higher peak intensity and width for Sr1.99Eu0.01SnO4 than Sr2Sn0.99Eu0.01O4. [ABSTRACT FROM AUTHOR]

A periodic exchange of energy between the light field and two level system is known as Rabi oscillations. The Bloch-Siegert shift (BSS) is a shift in Rabi oscillation resonance condition, when the driving field is sufficiently strong. There are new type of oscillations exhibit in Weyl semimetal at far from resonance, known as anomalous Rabi oscillation. In this work, we study the phenomenon of the Bloch-Siegert shift in Weyl semimetal at far from resonance called anomalous Bloch-Siegert shift (ABSS) by purely quantum mechanical treatment and describe it’s anisotropic nature. A fully numerical solution of the Floquet-Bloch equations unequivocally establishes the presence of not only anomalous Rabi oscillations in these systems but also their massless character. [ABSTRACT FROM AUTHOR]

We study the nonlinear optical properties of induced gapped bilayer graphene in presence of an optical field in two different regimes namely close to resonance and far-from resonance. Resonance means when the incident optical frequency is nearly equal to the inter-band transition frequency. The Rabi frequency is obtained in both the regimes - in the resonant case it is obtained by the well known rotating wave approximation (RWA) whereas far-from resonance it is obtained using an alternative to RWA called asymptotic RWA (ARWA), introduced by us for single layer graphene. Anomalous Rabi oscillations far from resonance are attributable to the pseudospin character of monolayer graphene as well as bilayer graphene. Branching of anomalous Rabi oscillations into single and bi-harmonic modes are characteristic of bilayer graphene absent in monolayer graphene and are attributed to the quadratic energy momentum relation in the bilayer system. [ABSTRACT FROM AUTHOR]

Powder of perovskite oxides BaSnO3 and Ba0.90Y0.10SnO3 have been synthesized by solution combustion method. Rietveld profile analysis shows that the phases crystallize with cubic unit cell in the space group pm3m. Further purity of the synthesized powders was checked by Fourier transform of infrared (FTIR) spectroscopy. The average grain size of the sintered samples was obtained using Scanning electron microscopy (SEM) and found to be 4.9 and 2.8 1m for BaSnO3 and Ba0.90Y0.10SnO3, respectively. The AC conductivity (σac) of synthesized samples was measured in the frequency range from 24Hz-1MHz and temperature range 100 - 600°C. Conductivity spectra of both the samples followed universal Johnscher’s power law at different temperatures. The value of bulk or dc conductivity (σdc) at different temperatures has been extracted by fitting the Johnscher’s power law to AC conductivity spectra. The activation energy for σc has been obtained from the least square linear fit of data points and found to be 0.53 eV and 0.43 eV, respectively for BaSnO3 and Ba0.90Y0.10SnO3. Based on the value of activation energy it is proposed that conduction in these samples is govern via hopping of (OH)•. The value of conductivity at temperature 550°C of Ba0.90Y0.10SnO3 is 0.00406 S-cm-1 higher than BaSnO3 (0.00173 S-cm-1) at the same temperature. [ABSTRACT FROM AUTHOR]

The Bloch-Siegert shift is a phenomenon in quantum optics, typically seen in two-level systems, when the driving field is sufficiently strong. The inclusion of frequency doubling effect (counter rotating term) in the conventional rotating wave approximation (RWA) changes the resonance condition thereby producing a rather small shift in the resonance condition, which is known as the Bloch-Siegert shift (BSS). Rabi oscillations in Dirac-Weyl fermionic systems exhibit anomalous behavior far from resonance, called anomalous Rabi oscillations. Therefore, in the present work, we study the phenomenon of the Bloch-Siegert shift in Weyl semimetal and topological insulator (TI) far from resonance, called anomalous Bloch-Siegert shift (ABSS). It is seen that the change in the resonance condition of anomalous Rabi oscillations is drastic in Weyl semimetal and TI. The ABSS in Weyl semimetals is highly anisotropic, whereas it is isotropic in TI. In case of TI, it is the Chern number which plays a crucial role to produce substantial change in the ABSS. [ABSTRACT FROM AUTHOR]

We study the non linear response of graphene in presence of quantum field in two different regimes. Far from resonance, using our new technique asymptotic rotating wave approximation (ARWA), we obtained that the matter field interaction leads to the slow oscillations like conventional Rabi oscillations observed in conventional semiconductors using well known rotating wave approximation (RWA). The Rabi frequency obtained in both the regimes. [ABSTRACT FROM AUTHOR]