34 research outputs found
Low-energy electronic properties of clean CaRuO: elusive Landau quasiparticles
We have prepared high-quality epitaxial thin films of CaRuO with residual
resistivity ratios up to 55. Shubnikov-de Haas oscillations in the
magnetoresistance and a temperature dependence in the electrical
resistivity only below 1.5 K, whose coefficient is substantially suppressed in
large magnetic fields, establish CaRuO as a Fermi liquid (FL) with
anomalously low coherence scale. Non-Fermi liquid (NFL) dependence is
found between 2 and 25 K. The high sample quality allows access to the
intrinsic electronic properties via THz spectroscopy. For frequencies below 0.6
THz, the conductivity is Drude-like and can be modeled by FL concepts, while
for higher frequencies non-Drude behavior, inconsistent with FL predictions, is
found. This establishes CaRuO as a prime example of optical NFL behavior in
the THz range.Comment: 12 pages, 21 figures including supplemental materia
Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)
The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer‐reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state‐of‐the‐art handbook for basic and clinical researchers.DFG, 389687267, Kompartimentalisierung, Aufrechterhaltung und Reaktivierung humaner Gedächtnis-T-Lymphozyten aus Knochenmark und peripherem BlutDFG, 80750187, SFB 841: Leberentzündungen: Infektion, Immunregulation und KonsequenzenEC/H2020/800924/EU/International Cancer Research Fellowships - 2/iCARE-2DFG, 252623821, Die Rolle von follikulären T-Helferzellen in T-Helferzell-Differenzierung, Funktion und PlastizitätDFG, 390873048, EXC 2151: ImmunoSensation2 - the immune sensory syste
Direct observation of the superconducting gap in thin film of titanium nitride using terahertz spectroscopy
We report on the charge carrier dynamics of superconducting titanium nitride (TiN) in the frequency range 90–510 GHz (3–17 cm−1). The experiments were performed on an 18-nm thick TiN film with a critical temperature of Tc=3.4 K. Measurements were carried out from room temperature down to 2 K, and in magnetic fields up to B=7 T. We extract the real and imaginary parts of the complex conductivity σ̂ as a function of frequency and temperature, directly providing the superconducting energy gap 2Δ. Further analysis yields the superconducting London penetration depth λL. The findings as well as the normal-state properties strongly suggest conventional BCS superconductivity, underlined by the ratio 2Δ(0)/kBTc=3.44. Detailed analysis of the charge carrier dynamics of the silicon substrate is also discussed
Structural Phase Transitions in Crystals: Phonons as Higgs and Goldstone Excitations
It has recently been indicated that optical and acoustic phonons can be identified with Higgs and Goldstone excitations of the crystal lattice arising from the spontaneous breaking of a global, continuous symmetry. Herein, this view is supported considering structural phase transitions induced by temperature, from the face-centered-cubic (fcc) phase of cobalt, and from the body-centered-cubic (bcc) phase of zirconium and titanium, to their hexagonal-close-packet (hcp) phase. The Higgs field potential is identified with the Ginzburg–Landau free energy difference calculated and available in the literature for the concerned structural phase transitions. In all the considered cases, the ensuing spontaneous symmetry breaking makes the optical phonon (identified with the Higgs mode) to arise only in the less symmetric hcp phase. This demonstrates Higgs excitations to be associated not only with quantum phase transitions, but also with structural phase transitions in natural crystals
Higgs and Goldstone modes in crystalline solids
In crystalline solids, the acoustic phonon can be described either as a Goldstone or as a non-Abelian gauge boson. However, the non-Abelianity of the related gauge group apparently makes the acoustic phonon a frequency-gapped mode, in contradiction with the other description. In a different perspective, overcoming this contradiction, both acoustic and optical phonon—the latter never appearing following the other two approaches—emerge, respectively, as the gapless Goldstone (phase) and the gapped Higgs (amplitude) fluctuation mode of an order parameter arising from the spontaneous breaking of a global symmetry, without invoking the gauge principle. In addition, the Higgs mechanism describes all the phonon–phonon interactions, including a possible perturbation of the acoustic phonon's frequency dispersion relation induced by the eventual optical phonon, a peculiar behavior that is able to produce mini-gaps inside the phonon Brillouin zone