Search results for "Drude model"

Dynamics of heavy fermions: Drude response in and

2006

While the effective mass of heavy fermions governs their thermodynamics, the optical properties are dominated by the characteristic relaxation rate which is expected to scale inversely with the effective mass. At the relaxation rate clear features, the so-called Drude response occur in the real and imaginary parts of the complex conductivity. Conventional optical spectroscopy can only indirectly probe the Drude response; thus we use novel broadband microwave spectroscopy to directly measure the frequency-dependent conductivity of UPd2Al3 and UNi2Al3 in the relevant frequency range and unambiguously observe the full low-energy electrodynamics of the heavy fermions including the Drude respons…

Extremely slow Drude relaxation of correlated electrons

2005

The electrical conduction of metals is governed by how freely mobile electrons can move throughout the material. This movement is hampered by scattering with other electrons, as well as with impurities or thermal excitations (phonons). Experimentally, the scattering processes of single electrons are not observed, but rather the overall response of all mobile charge carriers within a sample. The ensemble dynamics can be described by the relaxation rates, which express how fast the system approaches equilibrium after an external perturbation1,2,3. Here we measure the frequency-dependent microwave conductivity of the heavy-fermion metal UPd2Al3 (ref. 4), finding that it is accurately described…

Frequency-dependent conductivity of UPd2Al3 films

1998

The transmission of UPd2Al3 films was studied (4 K < T < 300 K) in the frequency range from 4 to 32 cm−1 by using a coherent source interferometer which allows for measuring both, amplitude and phase. In addition we report on radio frequency and optical measurements. Below 20 K the conductivity and dielectric constant show strong deviations from the behavior of a normal metal which cannot simply be explained by a single renormalized Drude model with an enhanced mass and reduced scattering rate. Instead, we find evidence for the opening of a pseudogap with a gap energy of 6 cm−1 and an extremely narrow ω = 0 mode which is responsible for the large DC conductivity.

2018

Damping distances of surface plasmon polariton modes sustained by different thin titanium nitride (TiN) films are measured at the telecom wavelength of 1.55 μm. The damping distances are correlated to the electrical direct current resistivity of the films sustaining the surface plasmon modes. It is found that TiN/Air surface plasmon mode damping distances drop non-linearly from 40 to 16μm as the resistivity of the layers increases from 28 to 130μΩ.cm, respectively. The relevance of the direct current (dc) electrical resistivity for the characterization of TiN plasmonic properties is investigated in the framework of the Drude model, on the basis of parameters extracted from spectroscopic ell…

Observing the anisotropic optical response of the heavy-fermion compound UNi2 Al3

2010

The optical conductivity of heavy fermions can reveal fundamental properties of the charge carrier dynamics in these strongly correlated electron systems. Here we extend the conventional techniques of infrared optics on heavy fermions by measuring the transmission and phase shift of THz radiation that passes through a thin film of UNi 2 Al 3 , a material with hexagonal crystal structure. We deduce the optical conductivity in a previously not accessible frequency range, and furthermore we resolve the anisotropy of the optical response (parallel and perpendicular to the hexagonal planes). At frequencies around 7 cm -1 , we find a strongly temperature-dependent and anisotropic optical conducti…

Direct observation of Drude behavior in the heavy-fermion by broadband microwave spectroscopy

2005

Abstract Previous optical studies on the heavy-fermion system UPd 2 Al 3 down to frequencies of about 1 cm - 1 ( = 30 GHz ) revealed a well-pronounced pseudogap at low frequencies (below 3 cm - 1 ) that was attributed to magnetic correlations. Thus, the optical conductivity at even lower frequencies is of notable interest because the Drude roll-off (the high-frequency characteristic of a metal which will give information on the quasiparticle dynamics) remained hidden at extremely low frequencies. Using a novel cryogenic broadband microwave spectrometer employing the Corbino geometry we have studied the complex optical conductivity of UPd 2 Al 3 thin films in the frequency range from 45 MHz …

Line shifts and broadenings in polarizable liquids

1989

We present a new dynamical derivation of the approximation used by Thompson, Schweizer, and Chandler and by Ho/ye and Stell for the frequency dependent polarizability of a quantum fluid with harmonically bound dipole moments; the Drude model. The derivation is the same for classical and quantum liquids—as is of course the result which agrees with that of these authors. We then refine the theory by taking account of the limited number of energy levels available, i.e., we replace the harmonic approximation by a two level approximation, for the target atom. This leads to a prefactor ω0I/ω0 in the line shift of an impurity atom in a fluid computed by Chandler, Schweitzer, and Wolynes: ω0 and ω0…