Saritha K. Nair

Ultrafast carrier dynamics in pristine and FeCl3-intercalated bilayer graphene

Ultrafast carrier dynamics of pristine bilayer graphene (BLG) and BLG intercalated with FeCl3 (FeCl3–G), were studied using time-resolved transient differential reflection (ΔR/R). Compared to BLG, the FeCl3–G data showed an opposite sign of ΔR/R, a slower rise time, and a single (instead of double) exponential relaxation. We attribute these differences in dynamics to the down-shifting in the Fermi level in FeCl3–G, as well as the formation of numerous horizontal bands arising from the d-orbitals of Fe. Our work shows that intercalation can dramatically change the electronic structure of graphene, and its associated carrier dynamics.Ultrafast carrier dynamics of pristine bilayer graphene (BLG) and BLG intercalated with FeCl3 (FeCl3–G), were studied using time-resolved transient differential reflection (ΔR/R). Compared to BLG, the FeCl3–G data showed an opposite sign of ΔR/R, a slower rise time, and a single (instead of double) exponential relaxation. We attribute these differences in dynamics to the down-shifting in the Fermi level in FeCl3–G, as well as the formation of numerous horizontal bands arising from the d-orbitals of Fe. Our work shows that intercalation can dramatically change the electronic structure of graphene, and its associated carrier dynamics.

Temperature-dependent terahertz conductivity of tin oxide nanowire films

Temperature-dependent terahertz conductivity of tin oxide (SnO2) nanowire films was measured from 10 to 300K using terahertz time-domain spectroscopy. The optical parameters, including the complex refractive index, optical conductivity and dielectric function, were obtained using a simple effective medium theory. The complex conductivity was fitted with the Drude-Smith model and the plasmon model. The results show that the carrier density (N) and plasmon resonance frequency (ω0) increase while the scattering time decreases with increasing temperature. The reduced carrier mobility compared with bulk SnO2 indicates the presence of carrier localization or trapping in these nanowires. (Some figures may appear in colour only in the online journal)

Temperature-dependent ultrafast carrier and phonon dynamics of topological insulator Bi1.5Sb0.5Te1.8Se1.2

Using ultrafast optical pump-probe technique, we studied the temperature-dependent carrier and phonon dynamics of the topological insulator Bi1.5Sb0.5Te1.8Se1.2 single-crystal from 10 K to 300 K. Two relaxation processes of carriers and coherent optical/acoustic phonons have been observed. By using the two-temperature model, we are able to attribute the fast (∼ps) relaxation component to carrier-phonon coupling involving carriers in the conduction band. We also studied the temperature dependence of the dephasing time and frequency of optical phonon, and the optical penetration depth of Bi1.5Sb0.5Te1.8Se1.2.

Ultrafast carrier phonon dynamics in NaOH-reacted graphite oxide film

NaOH-reacted graphite oxide film was prepared by decomposing epoxy groups in graphite oxide into hydroxyl and -ONa groups with NaOH solution. Ultrafast carrier dynamics of the sample were studied by time-resolved transient differential reflection (ΔR/R). The data show two exponential relaxation processes. The slow relaxation process (∼2ps) is ascribed to low energy acoustic phonon mediated scattering. The electron-phonon coupling and first-principles calculation results demonstrate that -OH and -ONa groups in the sample are strongly coupled. Thus, we attribute the fast relaxation process (∼0.17ps) to the coupling of hydroxyl and -ONa groups in the sample.

Quasiparticle dynamics in overdoped Bi1.4Pb0.7Sr1.9CaCU2O8+δ: Coexistence of superconducting gap and pseudogap below Tc

Photoexcited quasiparticle relaxation dynamics in overdoped Bi

Effect of annealing on the temperature-dependent dielectric properties of LaAlO3 at terahertz frequencies

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Doping dependence of the electron–phonon and electron–spin fluctuation interactions in the high-Tc superconductor Bi2Sr2CaCu2O8+δ

Sr

Ultrafast relaxation dynamics in BiFeO3/YBa2Cu3O7 bilayers

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Interfacial effects revealed by ultrafast relaxation dynamics in BiFeO

CaCu

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