An ac method for the precise measurement of <i>Q</i>-factor and resonance frequency of a microwave cavity

Nebendahl, B.; Peligrad, D.-N.; Požek, Miroslav; Dulčić, A.; Mehring, M.

doi:10.1063/1.1336823

Cited by 35 publications

(17 citation statements)

References 13 publications

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“…We performed complementary microwave (linear) conductivity experiments with a resonant cavity perturbation technique 69 extensively used to study cuprate superconductors 5,12 . The sample was mounted in an evacuated elliptical microwave cavity made of copper and immersed in a liquid helium bath.…”

Section: Methodsmentioning

confidence: 99%

Emergence of superconductivity in the cuprates via a universal percolation process

Pelc¹,

Vučković²,

Grbić³

et al. 2018

Nat Commun

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A pivotal step toward understanding unconventional superconductors would be to decipher how superconductivity emerges from the unusual normal state. In the cuprates, traces of superconducting pairing appear above the macroscopic transition temperature Tc, yet extensive investigation has led to disparate conclusions. The main difficulty has been to separate superconducting contributions from complex normal-state behaviour. Here we avoid this problem by measuring nonlinear conductivity, an observable that is zero in the normal state. We uncover for several representative cuprates that the nonlinear conductivity vanishes exponentially above Tc, both with temperature and magnetic field, and exhibits temperature-scaling characterized by a universal scale Ξ0. Attempts to model the response with standard Ginzburg-Landau theory are systematically unsuccessful. Instead, our findings are captured by a simple percolation model that also explains other properties of the cuprates. We thus resolve a long-standing conundrum by showing that the superconducting precursor in the cuprates is strongly affected by intrinsic inhomogeneity.

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Section: Methodsmentioning

confidence: 99%

Emergence of superconductivity in the cuprates via a universal percolation process

Pelc¹,

Vučković²,

Grbić³

et al. 2018

Nat Commun

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“…The setup is similar to the well-known microwave conductivity experiment5354 but uses RF excitation fields. The sample was mounted on a sapphire rod in a vacuum tube, with two coils wound around the tube and immersed in liquid helium.…”

Section: Methodsmentioning

confidence: 99%

Unconventional charge order in a co-doped high-Tc superconductor

et al. 2016

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Charge-stripe order has recently been established as an important aspect of cuprate high-Tc superconductors. However, owing to the complex interplay between competing phases and the influence of disorder, it is unclear how it emerges from the parent high-temperature state. Here we report on the discovery of an unconventional ordered phase between charge-stripe order and (pseudogapped) metal in the cuprate La1.8−xEu0.2SrxCuO4. We use three complementary experiments—nuclear quadrupole resonance, nonlinear conductivity and specific heat—to demonstrate that the order appears through a sharp phase transition and exists in a dome-shaped region of the phase diagram. Our results imply that the new phase is a state, which preserves translational symmetry: a charge nematic. We thus resolve the process of charge-stripe development in cuprates, show that this nematic phase is distinct from high-temperature pseudogap and establish a link with other strongly correlated electronic materials with prominent nematic order.

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“…The details of this method were published elsewhere. 52 Data acquisition was made during a slow temperature sweep of the sample so that the microwave signal generator could alternate between the resonance frequencies of the two modes. Thus, we obtained the experimental curves in both modes with a single temperature sweep.…”

Section: Methodsmentioning

confidence: 99%

Temperature range of superconducting fluctuations aboveTcin YBa2Cu
Grbić
¹
,
Požek
²
,
Paar
³

et al. 2011
Phys. Rev. B
92
16
92
2
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Microwave absorption measurements in magnetic fields from 0 up to 16 T were used to determine the temperature range of superconducting fluctuations above the superconducting critical temperature T c in YBa 2 Cu 3 O 7−δ . Measurements were performed on deeply underdoped, slightly underdoped, and overdoped single crystals. The temperature range of the superconducting fluctuations above T c is determined by an experimental method which is free from arbitrary assumptions about subtracting the nonsuperconducting contributions to the total measured signal and/or theoretical models to extract the unknown parameters. The superconducting fluctuations are detected in the ab plane, and c-axis conductivity, by identifying the onset temperature T . Within the sensitivity of the method, this fluctuation regime is found only within a fairly narrow region above T c . Its width increases from 7 K in the overdoped sample (T c = 89 K) to, at most, 23 K in the deeply underdoped sample (T c = 57 K), so that T falls well below the pseudogap temperature T * . Implications of these findings are discussed in the context of other experimental probes of superconducting fluctuations in the cuprates.

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An ac method for the precise measurement of Q-factor and resonance frequency of a microwave cavity

Cited by 35 publications

References 13 publications

Emergence of superconductivity in the cuprates via a universal percolation process

Emergence of superconductivity in the cuprates via a universal percolation process

Unconventional charge order in a co-doped high-Tc superconductor

Temperature range of superconducting fluctuations aboveTcin YBa2Cu
Grbić
¹
,
Požek
²
,
Paar
³

et al. 2011
Phys. Rev. B
92
16
92
2
View full text Add to dashboard Cite

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An ac method for the precise measurement of Q-factor and resonance frequency of a microwave cavity

Cited by 35 publications

References 13 publications

Emergence of superconductivity in the cuprates via a universal percolation process

Emergence of superconductivity in the cuprates via a universal percolation process

Unconventional charge order in a co-doped high-Tc superconductor

Temperature range of superconducting fluctuations aboveTcin YBa2CuGrbić1, Požek2, Paar3 et al. 2011Phys. Rev. B9216922View full textAdd to dashboardCite

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Temperature range of superconducting fluctuations aboveTcin YBa2Cu
Grbić
¹
,
Požek
²
,
Paar
³

et al. 2011
Phys. Rev. B
92
16
92
2
View full text Add to dashboard Cite