Contactless measurement of nonlinear conductivity in the radio-frequency range

Došlić, Marija; Pelc, Damjan; Požek, Miroslav

doi:10.1063/1.4890557

Cited by 4 publications

(4 citation statements)

References 13 publications

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“…Nonlinear planar response, for current flow along the CuO 2 planes, is measured with a sensitive contact-free method 30 (see Methods). The response can be analyzed by decomposing the signal into harmonics,where J is the response of the sample to an external field K (electric or magnetic), σ 1 the linear response tensor, and σ 2 , σ 3 , etc., the correction nonlinear tensors.…”

Section: Resultsmentioning

confidence: 99%

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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: Resultsmentioning

confidence: 99%

“…The sample is mounted on a sapphire holder with temperature control sensitivity better than 1 mK. The setup was previously tested under various conditions 30,67 . Notably, a similar methodology was used in the past to study the nonlinear Meissner effect at low temperatures 68 .…”

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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“…Due to high linear conductivity of doped cuprates, measuring σ 3 without significant unwanted heating effects is challenging. We have therefore developed a contactless pulse method [38], wherein currents are induced in the sample at some frequency ω (typically ∼ 20 MHz) and the response at 3ω (which is proportional to σ 3 ) is detected. Results of such a measurement are shown in Fig.…”

mentioning

confidence: 99%

“…The nonlinear conductivity setup and measurement procedure are described in detail in Ref. [38]. In experi-ments on LESCO we have used RF pulses at an excitation frequency of 18.8 MHz, with pulse lengths of 50 µs, repetition time 8 ms and maximum pulse power ∼ 100 W. Measurements were performed with the power varying from 10% to 100% full power, and the low power points adjusted to match at all temperatures to avoid baseline drift.…”

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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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Dependence of the critical temperature in overdoped copper oxides on superfluid density

Božović

et al. 2016

Nature

349

458

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The physics of underdoped copper oxide superconductors, including the pseudogap, spin and charge ordering and their relation to superconductivity, is intensely debated. The overdoped copper oxides are perceived as simpler, with strongly correlated fermion physics evolving smoothly into the conventional Bardeen-Cooper-Schrieffer behaviour. Pioneering studies on a few overdoped samples indicated that the superfluid density was much lower than expected, but this was attributed to pair-breaking, disorder and phase separation. Here we report the way in which the magnetic penetration depth and the phase stiffness depend on temperature and doping by investigating the entire overdoped side of the La2-xSrxCuO4 phase diagram. We measured the absolute values of the magnetic penetration depth and the phase stiffness to an accuracy of one per cent in thousands of samples; the large statistics reveal clear trends and intrinsic properties. The films are homogeneous; variations in the critical superconducting temperature within a film are very small (less than one kelvin). At every level of doping the phase stiffness decreases linearly with temperature. The dependence of the zero-temperature phase stiffness on the critical superconducting temperature is generally linear, but with an offset; however, close to the origin this dependence becomes parabolic. This scaling law is incompatible with the standard Bardeen-Cooper-Schrieffer description.

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Contactless measurement of nonlinear conductivity in the radio-frequency range

Cited by 4 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

Dependence of the critical temperature in overdoped copper oxides on superfluid density

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