Infrared vortex-state electrodynamics in type-II superconducting thin films

Xi, Xiaoxiang; Park, J.-H.; Graf, David; Carr, G. L.; Tanner, D. B.

doi:10.1103/physrevb.87.184503

Cited by 10 publications

(10 citation statements)

References 30 publications

(54 reference statements)

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“…We measured the reflectance ratios R(T )/R N (with R N being the 20 K normal state reflectance) by cycling the temperature up to 20 K and below T c down to 6 K, without moving the sample. This technique does indeed provide results which are intrinsically unaffected by possible misalignments between sample and reference, and is thus essential in detecting the often small effects due to the superconducting transition [22,23,12,24,25].…”

Section: Methodsmentioning

confidence: 99%

Two-band conductivity of a FeSe$_{0.5}$Te$_{0.5}$ film by reflectance measurements in the terahertz and infrared range

Perucchi¹,

Joseph²,

Caramazza³

et al. 2014

Supercond. Sci. Technol.

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Abstract. We report an infrared spectroscopy study of a 200 nm thick FeSe 0.5 Te 0.5 film grown on LaAlO 3 with T c =13.7 K. We analyze the 20 K normal state absolute reflectance R N measured over a broad infrared range and the reflectance ratio R S /R N , R S being the superconducting state reflectance, measured at 6 K in the terahertz range down to 12 cm −1 . We show that the normal state model conductivity is given by two Drude components, one of which much broader and intense than the other. In the superconducting state, we find that a gap ∆=37±3 cm −1 opens up in the narrow Drude band only, while the broad Drude band results to be ungapped, at least in the explored spectral range. Our results show that only a two-band model can coherently describe both normal and superconducting state data. ‡ Present address: Elettra Sincrotrone Trieste,

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Section: Methodsmentioning

confidence: 99%

Two-band conductivity of a FeSe$_{0.5}$Te$_{0.5}$ film by reflectance measurements in the terahertz and infrared range

Perucchi¹,

Joseph²,

Caramazza³

et al. 2014

Supercond. Sci. Technol.

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“…Terahertz (THz) waves have played an important role in both fundamental research and practical applications . Many low‐energy excitations can be effectively probed by THz waves, such as molecular rotation, lattice vibrations, Cooper pairs in superconductors, and THz plasmon polaritons in 2D electron gas, THz radar, wireless communication, and imaging systems have advantages over the microwave counterparts for higher spatial resolution, broader bandwidth, and higher data rates . However, in order to take full advantage of THz waves, there is an urgent need in developing functional THz materials to construct various kinds of THz devices and components.…”

Section: Introductionmentioning

confidence: 99%

Anomalous Terahertz Reflection and Scattering by Flexible and Conformal Coding Metamaterials

Liu

Yang

et al. 2015

Advanced Optical Materials

189

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Arbitrary control of terahertz (THz) waves remains a significant challenge although it promises many important applications. Here, a method to tailor the reflection and scattering of THz waves in an anomalous manner by using 1‐bit coding metamaterials is presented. Specific coding sequences result in various THz far‐field reflection and scattering patterns, ranging from a single beam to two, three, and numerous beams, which depart obviously from the ordinary Snell's law of reflection. By optimizing the coding sequences, a wideband THz thin film metamaterial with extremely low specular reflection, due to the scattering of the incident wave into various directions, is demonstrated. As a result, the reflection from a flat and flexible metamaterial can be nearly uniformly distributed in the half space with small intensity at each specific direction, manifesting a diffuse reflection from a rough surface. Both simulation and experimental results show that a reflectivity less than −10 dB is achieved over a wide frequency range from 0.8 to 1.4 THz, and it is insensitive to the polarization of the incident wave. This work reveals new opportunities arising from coding metamaterials in effective manipulation of THz wave propagation and may offer widespread applications.

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“…TDTS measurements were performed in transmission geometry on thin films of varying thicknesses ranging from 70 -130 nm. The 70 nm β−W thin-films had the highest T c 's of ∼ 3.7 K. The samples on both Si and MgO substrates gave similar results (See Supplementary Material [15][16][17][18][19][20] (SM)). Both real and imaginary parts of the complex conductance, G(ν), were extracted from the c omplex transmission measured in TDTS measurements, performed down to 1.6 K 21 .…”

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confidence: 90%

“…In order to confirm the presence of inhomogeneity, we analyze the system in terms of effective medium models. We compare the conductivity with calculations based on two different effective medium models, namely the Bruggeman-effective-medium-approximation (BEMA) 27 and Maxwell-Garnett theory (MGT) 16 , for the collective response of a mixture of two materials 17,21,28 . See SM 15 for details of these models.…”

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confidence: 99%

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Anomalously small superconducting gap in the strong spin-orbit coupled superconductor: $ β- $Tungsten

Chauhan,

Budhani,

Armitage

2021

Preprint

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Thin films of β−tungsten host superconductivity in the presence of strong spin-orbit coupling. This non-equilibrium crystalline phase of tungsten has attracted considerable attention in recent years due to its giant spin Hall effect and the potential promise of exotic superconductivity. However, more than 60 years after its discovery, superconductivity in this material is still not well understood. Using time-domain THz spectroscopy, we measure the frequency response of the complex optical conductivity of β−tungsten thin film with a Tc of 3.7 K in its superconducting state. At temperatures down to 1.6 K, we find that both the superconducting gap and the superfluid spectral weight are much smaller than that expected for a weakly coupled superconductor given the Tc. The conclusion of a small gap holds up even when accounting for possible inhomogeneities in the system, which could come from other crystalline forms of tungsten (that are not superconducting at these temperatures) or surface states on β−tungsten grains. Using detailed X-ray diffraction measurements, we preclude the possibility of significant amount of other tungsten allotropes, strongly suggesting the topological surface states of β−tungsten play the role of inhomogeneity in these films. Our observations pose a challenge and opportunity for a theory of strongly anisotropic normal metals with strong spin-orbit coupling to describe.

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Infrared vortex-state electrodynamics in type-II superconducting thin films

Cited by 10 publications

References 30 publications

Two-band conductivity of a FeSe$_{0.5}$Te$_{0.5}$ film by reflectance measurements in the terahertz and infrared range

Two-band conductivity of a FeSe$_{0.5}$Te$_{0.5}$ film by reflectance measurements in the terahertz and infrared range

Anomalous Terahertz Reflection and Scattering by Flexible and Conformal Coding Metamaterials

Anomalously small superconducting gap in the strong spin-orbit coupled superconductor: $ β- $Tungsten

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