Stripline resonators for cryogenic microwave spectroscopy on metals and superconductors

Scheffler, Marc; Fella, Christian; Dressel, Martin

doi:10.1088/1742-6596/400/5/052031

Cited by 13 publications

(13 citation statements)

References 13 publications

(18 reference statements)

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“…[ [45][46][47][48]. A stripline is formed by a planar center conductor, sandwiched between two dielectrics followed by two ground planes, as shown in the schematic drawing of Fig.…”

Section: Methodsmentioning

confidence: 99%

Complete electrodynamics of a BCS superconductor with μeV energy scales: Microwave spectroscopy on titanium at mK temperatures

2018

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We performed resonant microwave measurements on superconducting titanium (Ti) down to temperatures of 40 mK, well below its critical temperature Tc ≈ 0.5 K. Our wide frequency range 3.3-40 GHz contains the zero-temperature energy gap 2∆0 and allows us to probe the full electrodynamics of the superconducting state, including excitations across the gap and the low-frequency responses of superfluid condensate and thermal quasiparticles. The observed behavior follows the predictions of the BCS-based Mattis-Bardeen formalism, which implies that superconducting Ti is in the dirty limit, in agreement with our determination of the scattering rate. We directly determine the temperature dependence of the energy gap, which is in accordance with BCS predictions, and 2∆0/kBTc ≈ 3.5 with ∆0 ≈ 75 µeV. We also evaluate the penetration depth, and we characterize the behavior of superconducting Ti in external magnetic field.

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“…[ [45][46][47][48]. A stripline is formed by a planar center conductor, sandwiched between two dielectrics followed by two ground planes, as shown in the schematic drawing of Fig.…”

Section: Methodsmentioning

confidence: 99%

Complete electrodynamics of a BCS superconductor with μeV energy scales: Microwave spectroscopy on titanium at mK temperatures

2018

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“…However, preliminary tests showed that the calibration of such an experiment is rather difficult. Therefore, we employ a different technique 31, 32: by fabricating two gaps into the center conductor which reflect most of the microwave signal, we create a one‐dimensional Fabry‐Perot resonator. The resonator can be designed in such a way that its quality factor is governed by the sample of interest.…”

Section: Microwave Spectroscopymentioning

confidence: 99%

Microwave spectroscopy on heavy‐fermion systems: Probing the dynamics of charges and magnetic moments

Scheffler

Schlegel

Clauss

et al. 2013

Physica Status Solidi (b)

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Investigating solids with light gives direct access to charge dynamics, electronic and magnetic excitations. For heavy fermions, one has to adjust the frequency of the probing light to the small characteristic energy scales, leading to spectroscopy with microwaves. We review general concepts of the frequency-dependent conductivity of heavy fermions, including the slow Drude relaxation and the transition to a superconducting state, which we also demonstrate with experimental data taken on UPd 2 Al 3 . We discuss the optical response of a Fermi liquid and how it might be observed in heavy fermions. Microwave studies with focus on quantum criticality in heavy fermions concern the charge response, but also the magnetic moments can be addressed via electron spin resonance (ESR). We discuss the case of YbRh 2 Si 2 , the open questions concerning ESR of heavy fermions, and how these might be addressed in the future. This includes an overview of the presently available experimental techniques for microwave studies on heavy fermions, with a focus on broadband studies using the Corbino approach and on planar superconducting resonators.

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“…Studying conducting materials is also our motivation for the development of superconducting Pb stripline resonators that can act as compact and sensitive probes in cryogenic microwave spectroscopy [36][37][38]. Here Pb with T c ≈ 7.2 K and a critical magnetic field of about B c ≈ 80 mT is a well suited basis material [39], as it can be processed for thin films rather easily.…”

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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Stripline resonators for cryogenic microwave spectroscopy on metals and superconductors

Cited by 13 publications

References 13 publications

Complete electrodynamics of a BCS superconductor with μeV energy scales: Microwave spectroscopy on titanium at mK temperatures

Complete electrodynamics of a BCS superconductor with μeV energy scales: Microwave spectroscopy on titanium at mK temperatures

Microwave spectroscopy on heavy‐fermion systems: Probing the dynamics of charges and magnetic moments

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

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