Microwave conductivity of heavy fermions in UPd2Al3

Scheffler, Marc; Dressel, Martin; Jourdan, Martin

doi:10.1140/epjb/e2010-00085-6

Cited by 24 publications

(26 citation statements)

References 42 publications

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“…Microwave spectroscopy in condensed matter physics is yet another resonator application. For many materials of present research, such as magnetic and heavy-fermion materials, there exist important low energy scales that can be accessed with microwave spectroscopy [20][21][22][23][24][25], and a very prominent case here is the vast range of conventional and unconventional superconductors, including cuprate, pnictide, organic, heavy-fermion, and strongly disordered superconductors [26][27][28][29]. To this end, a variety of different microwave spectroscopy techniques have been developed [30][31][32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

Superconducting Pb stripline resonators in parallel magnetic field and their application for microwave spectroscopy

Ebensperger¹,

Thiemann²,

Dressel³

et al. 2016

Supercond. Sci. Technol.

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Abstract. Planar superconducting microwave resonators are key elements in a variety of technical applications and also act as sensitive probes for microwave spectroscopy of various materials of interest in present solid state research. Here superconducting Pb is a suitable material as a basis for microwave stripline resonators.To utilize Pb stripline resonators in a variable magnetic field (e.g. in ESR measurements), the electrodynamics of such resonators in finite magnetic field has to be well understood. Therefore we performed microwave transmission measurements (with ample applied power to work in linear response) on superconducting Pb stripline resonators in a variable, parallel magnetic field. We determined surface resistance, penetration depth as well as real and imaginary parts, σ 1 and σ 2 , of the complex conductivity of superconducting Pb as a function of magnetic field. Here we find features reminiscent of those in temperaturedependent measurements, such as a maximum in σ 1 (coherence peak). At magnetic fields above the critical field of this type-I superconductor we still find a low-loss microwave response, which we assign to remaining superconductivity in the form of filaments within the Pb. Hysteresis effects are found in the quality factor of resonances once the swept magnetic field has exceeded the critical magnetic field. This is due to normal conducting areas that are pinned and can therefore persist in the superconducting phase. Besides zero-field-cooling we show an alternative way to eliminate these even at T < Tc. Based on our microwave data, we also determine the critical magnetic field and the critical temperature of Pb in a temperature range between 1.6K and 6.5K and magnetic fields up to 140mT, showing good agreement with BCS predictions. We furthermore study a Sn sample in a Pb resonator to demonstrate the applicability of superconducting Pb stripline resonators in the experimental study of other (super-)conducting materials in a variable magnetic field.

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Section: Introductionmentioning

confidence: 99%

Superconducting Pb stripline resonators in parallel magnetic field and their application for microwave spectroscopy

Ebensperger¹,

Thiemann²,

Dressel³

et al. 2016

Supercond. Sci. Technol.

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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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“…Optical spectroscopy measurements at GHz and THz frequencies have already shown complex low energy features linked to magnetic excitations in different uranium systems [16][17][18][19][20]. In the time domain, ultrafast optical spectroscopy (UOS) has also been quite successful in providing such information, offering insight into the physics of strongly correlated materials [21] such as superconductors (SCs) [22][23][24] and heavy fermions (HFs) [25,26].…”

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confidence: 99%