Optical reflectivity spectra of La1−xSrxMnO3 (0≤x≤0.30) were measured on cleavage surfaces of single crystals. The optical conductivity σ(ω) of ferromagnetic-metal La0.70Sr0.30MnO3 is characterized by a Drude-like − but not simple-Drude − component with large spectral weight below ∼1.6 eV, which yields a large effective carrier number N eff consistent with the results of Hall coefficient and sp...

We study the persistent current and the Drude weight of a system of spinless fermions, with repulsive interactions and a hopping impurity, on a mesoscopic ring pierced by a magnetic flux, using a Density Matrix Renormalization Group algorithm for complex fields. Both the Luttinger Liquid (LL) and the Charge Density Wave (CDW) phases of the system are considered. Under a Jordan-Wigner transforma...

Terahertz time-domain spectroscopy is used to measure the complex conductivity of nanometer-thick gold films evaporated on silicon substrates in the far-infrared spectral region from 0.2 to 2.7 THz. With increasing film thickness a characteristic crossover from an insulating to a conducting state via a percolation transition is observed. Of particular interest is the characteristic non-Drude be...

The linear response theory for current is investigated in a variational context. Expressions are derived for the Drude and superfluid weights for general variational wavefunctions. The expression for the Drude weight highlights the difficulty in its calculation since it depends on the exact energy eigenvalues which are usually not available in practice. While the Drude weight is not available i...

Beta gallium oxide, ?-Ga2O3, is one of the promising ultrawide bandgap semiconductors with a monoclinic (C2/m) ?-phase structure showing strong anisotropic properties. To improve performance these devices, more optical characterization required. Here, carrier dynamics in optically excited (010) oriented Fe-doped ?-Ga2O3 was studied by terahertz time-domain spectroscopy. An 800 nm continuous-wav...

The situation with the temperature corrections to the Casimir force between real metals of finite conductivity is reported. It is shown that the plasma dielectric function is well adapted to the Lifshitz formula and leads to reasonable results for real conductors. The Drude dielectric function which describes media with dissipation is found not to belong to the application range of the Lifshitz...

Using terahertz time-domain spectroscopy, the real part of optical conductivity [σ(1)(ω)] of twisted bilayer graphene was obtained at different temperatures (10-300 K) in the frequency range 0.3-3 THz. On top of a Drude-like response, we see a strong peak in σ(1)(ω) at ~2.7 THz. We analyze the overall Drude-like response using a disorder-dependent (unitary scattering) model, then attribute the ...

A resonant-state expansion (RSE) for open optical systems with a general frequency dispersion of the permittivity is presented. The RSE of dispersive systems converts Maxwell’s wave equation into a linear matrix eigenvalue problem in the basis of unperturbed resonant states, in this way numerically exactly determining all relevant eigenmodes of the optical system. The dispersive RSE is verified...

Ultrafast carrier dynamics in InGaN/GaN multiple quantum wells is measured by time-resolved terahertz spectroscopy. The built-in piezoelectric field is initially screened by photoexcited, polarized carriers, and is gradullay restored as the carriers recombine. We observe a nonexponential decay of the carrier density. Time-integrated photoluminescence spectra have shown a complete screening of t...

We report on the first single-state measurement of the broadband (450-800 nm) dielectric function of gold isochorically heated by a femtosecond laser pulse to energy densities of 10(6) - 10(7) J/kg. A Drude and an interband component are clearly seen in the imaginary part of the dielectric function. The Drude component increases with energy density while the interband component shows both enhan...