Extremely slow Drude relaxation of correlated electrons

Scheffler, Marc; Dressel, Martin; Jourdan, Martin; Adrian, H.

doi:10.1038/nature04232

Cited by 107 publications

(101 citation statements)

References 21 publications

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“…Knowledge of the dielectric function gives insight into fundamental electronic interactions in regular metals or strongly correlated electron systems, e.g. heavy-fermion compounds with high effective mass and resulting low electron relaxation rate [5].…”

Section: Introductionmentioning

confidence: 99%

Optical dielectric function of gold

et al. 2012

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In metal optics gold assumes a special status because of its practical importance in opto-electronic and nano-optical devices, and its role as a model system for the study of the elementary electronic excitations that underlie the interaction of electromagnetic fields with metals. However, largely inconsistent values for the frequency dependence of the dielectric function describing the optical response of gold are found in the literature [1][2][3]. We performed precise spectroscopic ellipsometry measurements on evaporated gold, template-stripped gold, and single-crystal gold to determine the optical dielectric function across a broad spectral range of 300 nm -25 µm (0.05 -4.14 eV) with high spectral resolution. We fit the data to the Drude free-electron model, with an electron relaxation time τD = 14 ± 3 fs and plasma energy ωp = 8.48 eV. We find that the variation in dielectric functions for the different types of samples is small compared to the range of values reported in the literature. Our values, however, are comparable to the aggregate mean of the collection of previous measurements from over the past six decades. This suggests that although some variation can be attributed to surface morphology, the past measurements using different approaches seem to have been plagued more by systematic errors than previously assumed.

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Section: Introductionmentioning

confidence: 99%

Optical dielectric function of gold

et al. 2012

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“…Unfortunately, so far there is no technique available that fulfills all of these options: Corbino reflection spectroscopy is applicable in extremely broad frequency ranges (up to 40 GHz) 5,6 and at cryogenic temperatures, [7][8][9][10] is phase-sensitive, and has been used in the study of conventional and exotic superconductors [11][12][13][14][15] , correlated metals, [16][17][18] , and materials close to a transition between conductive and insulating states. 19 While the Corbino approach is applicable for bulk samples of lossy conductors, 9,19,20 its comparably poor sensitivity restricts its applicability for highly conductive metals and superconductors to geometrically strongly confined samples, 6,7,9 such as thin films.…”

Section: Introductionmentioning

confidence: 99%

Surface-resistance measurements using superconducting stripline resonators

Hafner

Dressel

Scheffler

2014

Review of Scientific Instruments

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We present a method to measure the absolute surface resistance of conductive samples at a set of GHz frequencies with superconducting lead stripline resonators at temperatures 1 -6 K. The stripline structure can easily be applied for bulk samples and allows direct calculation of the surface resistance without the requirement of additional calibration measurements or sample reference points. We further describe a correction method to reduce experimental background on high-Q resonance modes by exploiting TEM-properties of the external cabling. We then show applications of this method to the reference materials gold, tantalum, and tin, which include the anomalous skin effect and conventional superconductivity. Furthermore, we extract the complex optical conductivity for an all-lead stripline resonator to find a coherence peak and the superconducting gap of lead.

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“…These fits are highly constrained by the use of both THz and dc data. Implicit in this fitting is the reasonable assumption that there are no spectral peaks in σ 1 below the lower end of our measured range [14,27,28]. The fact that we cannot fit our data with a single term Drude model demonstrates that the transport cannot be described by a single energy-independent relaxation time.…”

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confidence: 89%

Anomalous frequency and temperature-dependent scattering and Hund's coupling in the almost quantum critical heavy-fermion systemCeFe2Ge2

Bosse

Pan

et al. 2016

Phys. Rev. B

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We present THz range optical conductivity data of a thin film of the near quantum critical heavy fermion compound CeFe2Ge2. Our complex conductivity measurements find a deviation from conventional Drude-like transport in a temperature range previously reported to exhibit unconventional behavior. We calculate the frequency dependent effective mass and scattering rate using an extended Drude model analysis. We find the inelastic scattering rate can be described by a temperature dependent power-law ω n(T ) where n(T ) approaches ∼ 1.0 ± 0.2 at 1.5 K. This is compared to the ρ ∼ T 1.5 behavior claimed in dc resistivity data and the ρ ∼ T 2 expected from Fermi-liquid theory. In addition to a low temperature mass renormalization, we find an anomalous mass renormalization that persists to high temperature. We attribute this to a Hund's coupling in the Fe states in a manner similar to that recently proposed in the ferro-pnictides. CeFe2Ge2 appears to be a very interesting system where one may study the interplay between the usual 4f lattice Kondo effect and this Hund's enhanced Kondo effect in the 3d states.

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Extremely slow Drude relaxation of correlated electrons

Cited by 107 publications

References 21 publications

Optical dielectric function of gold

Optical dielectric function of gold

Surface-resistance measurements using superconducting stripline resonators

Anomalous frequency and temperature-dependent scattering and Hund's coupling in the almost quantum critical heavy-fermion systemCeFe2Ge2

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