Laser scanning microscopy of HTS films and devices (Review Article)

Zhuravel, A. P.; Sivakov, A. G.; Турутанов, О. Г.; Omelyanchouk, A. N.; Anlage, Steven M.; Lukashenko, A.; Ustinov, A. V.; Abraimov, D.

doi:10.1063/1.2215376

Cited by 62 publications

(71 citation statements)

References 61 publications

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“…Details of the RF and laser excitations of the spirals have been previously published [29,[31][32][33]. The spiral develops a photoresponse due to pair-breaking and localized heating, producing a change in its resonant frequency and quality factor [37,38]. The laser intensity is modulated at 100 kHz, and the changes in RF transmission at a fixed frequency are phase sensitively detected, resulting in a photoresponse (PR) signal consisting of both a magnitude and phase.…”

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confidence: 99%

Imaging the Anisotropic Nonlinear Meissner Effect in NodalYBa2Cu3O7−δThin-Film Superconductors

et al. 2013

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We have directly imaged the anisotropic nonlinear Meissner effect in an unconventional superconductor through the nonlinear electrodynamic response of both (bulk) gap nodes and (surface) Andreev bound states. A superconducting thin film is patterned into a compact self-resonant spiral structure, excited near resonance in the radio-frequency range, and scanned with a focused laser beam perturbation. At low temperatures, direction-dependent nonlinearities in the reactive and resistive properties of the resonator create photoresponse that maps out the directions of nodes, or of bound states associated with these nodes, on the Fermi surface of the superconductor. The method is demonstrated on the nodal superconductor YBa2Cu3O 7−δ and the results are consistent with theoretical predictions for the bulk and surface contributions.Introduction -The Meissner effect is the spontaneous exclusion of magnetic flux from the bulk of a superconductor and is one of the hallmarks of superconductivity. In the presence of a magnetic field, a superconductor must invest kinetic energy in a supercurrent flow to screen out the applied field. This reduces the free energy difference between the superconducting and normal states, resulting in a reduction in magnitude of the superconducting order parameter. This in turn leads to a field-and current-dependent magnetic penetration depth, diamagnetic moment, etc. and is referred to as the nonlinear Meissner effect (NLME). Microscopically the NLME arises when Cooper pairs at the leading edge of the current-carrying Fermi surface can de-pair into available quasi-particle states at the back-end and create a quasi-particle backflow current [1]. Conventional (fully gapped) superconductors show the strongest nonlinearities near T c , and have exponentially suppressed nonlinear response at low temperatures, T ≪ T c . Unconventional superconductors with nodes in the superconducting energy gap are expected to have a strong nonlinear Meissner effect at low temperatures, due to the nodal excitations out of the superconducting ground state [2]. In addition this nonlinear response should be anisotropic, reflecting the locations of nodes of the gap on the Fermi surface.

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Imaging the Anisotropic Nonlinear Meissner Effect in NodalYBa2Cu3O7−δThin-Film Superconductors

et al. 2013

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“…Our measurements indicate that the device performance is limited by reflections between the superconducting parts on the chip and the normal conducting microwave connectors. This conclusion is based on our data obtained by low temperature laser scanning microscopy (LTLSM) 14,15 . Our experiments indicate that our hybrid ring couplers are highly suitable for integration into superconducting circuit QED experiments 16 , ultimately allowing for studies of propagating quantum microwaves [11][12][13] and applications in quantum information processing.…”

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confidence: 75%

“…To explore these artifacts, we visualize the effects of reflections by measuring the response of a hybrid ring on a silicon substrate to local heating by a focused laser beam. This method is known as low temperature laser scanning microscopy 14 . In these experiments, a focused laser beam is scanned across the chip surface and the change in the transmission parameter S 42 is recorded as function of the beam position.…”

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A superconducting 180° hybrid ring coupler for circuit quantum electrodynamics

Hoffmann

Deppe

Niemczyk

et al. 2010

Applied Physics Letters

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Superconducting circuit quantum electrodynamics experiments with propagating microwaves require devices acting as beam splitters. Using niobium thin films on silicon and sapphire substrates, we fabricated superconducting 180 • microstrip hybrid ring couplers, acting as beam splitters with center frequencies of about 6 GHz. For the magnitude of the coupling and isolation we find −3.5 ± 0.5 dB and at least −15 dB, respectively, in a bandwidth of 2 GHz. We also investigate the effect of reflections at the superconductor-normal conductor contact by means of low temperature laser scanning microscopy. Our measurements show that our hybrid rings are well suited for on-chip applications in circuit quantum electrodynamics experiments.In superconducting circuit quantum electrodynamics (QED) 1-3 , intracavity microwave photons interact with solid-state artificial atoms 4-6 . Both cavity and atom are realized by superconducting quantum circuits on a chip with characteristic frequencies in the microwave regime (1-10 GHz). Recently, this field has been extended towards the study of propagating quantum microwaves. To this end, quantum optical techniques such as optical homodyne tomography 7 or photon-based quantum information processing and communication 8,9 are being adapted to the microwave regime. One key element for the transformation from the optical to the microwave regime is the implementation of a beam splitter which is understood on the quantum level 10 . This allows the use of signal recovery techniques employing two amplifier chains and eliminating the (not yet available) single microwave photon detectors 11 . Hereby, photon correlations can be accessed and all quadrature moments of propagating quantum microwaves and, simultaneously, those of the detector noise can be extracted 12 . The very same idea was recently used to characterize the black body radiation emitted by a 50 Ω load resistor 13 . Ideally, in experiments with propagating quantum microwaves a beam splitter has to be lossless. A device matching these conditions is the 180 • hybrid ring which is entirely based on interference effects. Usually, microwave beam splitters are realized as normal conductive devices. However, for superconducting circuit QED the on-chip implementation of the beam splitter and the superconducting quantum devices under investigation would be favorable, avoiding reflections between various circuit parts and minimizing interconnect losses. In this letter, we present a detailed study on low-loss superconducting hybrid rings fabricated from niobium microstrip lines on both silicon and sapphire substrates. For the magnitude of the coupling and isolation we find −3.5 ± 0.5 dB and better than −15 dB in a bandwidth of up to 2 GHz, respectively. We note that the isolation increases when reducing the bandwidth, reaching a maximum value of better than −60 dB at the center frequency. Our measurements indicate that the device performance is limited by reflections between the superconducting parts on the chip and the normal conducting microwave...

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“…The values of d T and τ at 4.2 K in thin film HTS studied with LTLSM range between 1-10 μm and 0.1-10 μs. 25 The spatial resolution can be estimated as 6 …”

Section: Discussionmentioning

confidence: 99%

“…Low temperature laser scanning microscopy (LTLSM) is a well-known technique to characterize loss mechanisms in high-temperature superconductors (HTS). 6 The origins of the technique go back to electron-beam heating 7 and visualization of low-frequency transport processes and vortex motion in superconductors. 8 Later the method was adapted to laser heating and measurement of high frequency transport processes.…”

Section: Introductionmentioning

confidence: 99%

Low temperature laser scanning microscopy of a superconducting radio-frequency cavity

Ciovati

Anlage

Baldwin

et al. 2012

Review of Scientific Instruments

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An apparatus was developed to obtain, for the first time, 2D maps of the surface resistance of the inner surface of an operating superconducting radio-frequency niobium cavity by a low-temperature laser scanning microscopy technique. This allows identifying non-uniformities of the surface resistance with a spatial resolution of about one order of magnitude better than with earlier methods and surface resistance resolution of ~ 1  at 3.3 GHz. A signal-to-noise ratio of about 10 dB was obtained with 240 mW laser power and 1 Hz modulation frequency. The various components of the apparatus, the experimental procedure and results are discussed in detail in this contribution.

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Laser scanning microscopy of HTS films and devices (Review Article)

Cited by 62 publications

References 61 publications

Imaging the Anisotropic Nonlinear Meissner Effect in NodalYBa2Cu3O7−δThin-Film Superconductors

Imaging the Anisotropic Nonlinear Meissner Effect in NodalYBa2Cu3O7−δThin-Film Superconductors

A superconducting 180° hybrid ring coupler for circuit quantum electrodynamics

Low temperature laser scanning microscopy of a superconducting radio-frequency cavity

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