Charge transport in normal metal–magnesiumdiboride junctions

Brinkman, Alexander; Ploeg, S. H. W. van der; Golubov, Alexandre Avraamovitch; Rogalla, Horst; Kim, T.H.; Moodera, J. S.

doi:10.1016/j.jpcs.2005.10.013

Cited by 14 publications

(19 citation statements)

References 20 publications

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“…We note that the estimates for bare Leggett's mode frequency ! L are close to the 6:2 meV value observed by tunneling spectroscopy [31] and the estimates for the peak in Raman response (6), ! LR , are consistent with the observed mode at 9.4 meV.…”

supporting

confidence: 86%

Observation of Leggett’s Collective Mode in a MultibandMgB2Superconductor

Blumberg¹,

Mialitsin²,

Dennis³

et al. 2007

Phys. Rev. Lett.

129

132

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We report observation of Leggett's collective mode in a multiband MgB2 superconductor with Tc=39 K arising from the fluctuations in the relative phase between two superconducting condensates. The novel mode is observed by Raman spectroscopy at 9.4 meV in the fully symmetric scattering channel. The observed mode frequency is consistent with theoretical considerations based on first-principles computations.

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supporting

confidence: 86%

Observation of Leggett’s Collective Mode in a MultibandMgB2Superconductor

Blumberg¹,

Mialitsin²,

Dennis³

et al. 2007

Phys. Rev. Lett.

129

132

View full text Add to dashboard Cite

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“…Its double-gap structure originates from an electronic structure around the Fermi energy that comprises σ and π bands [33][34][35] . Observation of the Leggett mode in MgB 2 has been reported with tunneling spectroscopy 36 , Raman spectroscopy 37,38 and angle-resolved photoemission spectroscopy 39 , while no report has so far been made for the Higgs mode. A more recent family of superconductors, the iron pnictides with high T c s, also have multi-orbital and multi-gap structures, where the electron correlation is suggested 40,41 to bring about s ± and s ++ pairings depending on the chemical composition and/or doping level 42,43 .…”

Section: Introductionmentioning

confidence: 99%

Theory of light-induced resonances with collective Higgs and Leggett modes in multiband superconductors

2017

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We theoretically investigate coherent optical excitations of collective modes in two-band BCS superconductors, which accommodate two Higgs modes and one Leggett mode corresponding, respectively, to the amplitude and relative-phase oscillations of the superconducting order parameters associated with the two bands. We find, based on a mean-field analysis, that each collective mode can be resonantly excited through a nonlinear light-matter coupling when the doubled frequency of the driving field coincides with the frequency of the corresponding mode. Among the two Higgs modes, the higher-energy one exhibits a sharp resonance with light, while the lower-energy mode has a broadened resonance width. The Leggett mode is found to be resonantly induced by a homogeneous ac electric field because the leading nonlinear effect generates a potential offset between the two bands that couples to the relative phase of the order parameters. The resonance for the Leggett mode becomes sharper with increasing temperature. All of these light-induced collective modes along with density fluctuations contribute to the third-harmonic generation. We also predict an experimental possibility of optical detection of the Leggett mode.

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“…Finally, we remark that the present theoretical prediction relies on the coexistence of the Josephson-plasma and the JL modes. Since observation of Leggett's mode in a bulk MgB 2 sample has been reported 32 and in junctions with MgB 2 33,34 , we expect that such a collective mode can be detected in a junction system and the theory will be verified experimentally.…”

mentioning

confidence: 67%

Macroscopic quantum tunneling in multigap superconducting Josephson junctions: Enhancement of escape rate via quantum fluctuations of the Josephson-Leggett mode

2011

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We theoretically study the macroscopic quantum tunneling (MQT) in a hetero Josephson junction formed by a conventional single-gap superconductor and a multigap superconductor such as and ironbased superconductors and MgB 2 . In such a Josephson junction more than one phase difference is defined. We clarify their phase dynamics and construct a theory for the MQT in the multigap Josephson junctions. The dynamics of the phase differences are strongly affected by the JosephsonLeggett mode, which is the out-of-phase oscillation mode of the phase differences. The escape rate is calculated in terms of the effective action renormalized by the Josephson-Leggett mode at zero-temperature limit. We successfully predict drastic enhancement of the escape rate when the frequency of the Josephson-Leggett mode is less than the Josephson-plasma frequency.PACS numbers: 74.50.+r Macroscopic quantum tunneling (MQT)1-4 is a counterintuitive phenomenon in quantum mechanics appearing in a macroscopic level and has been observed in various fields of physics such as condensed matters, nuclei, cosmology, etc. This phenomenon has still attracted a great interest in physics communities. In particular, the MQT in Josephson junctions, which is observed in a switching event at low temperature 3,4 , has been intensively studied because it is promising for applications to a Josephson phase qubit 5-7 .In this paper we explore the physics of MQT in an unexplored type of Josephson junctions which has multiple tunneling channels. Such a Josephson junction can be fabricated by using recently discovered iron-based superconductors 8-10 or MgB 2 11-13 , because these superconductors are multiband ones having more than one disconnected Fermi surfaces and the superconducting gap can be individually well defined on each Fermi surface. In a Josephson junction made of multigap superconductors one may expect that the superconducting tunneling current has multiple channels between the two superconducting electrodes 14-17 . We construct a theory for the quantum switching (i.e., MQT) in Josephson junctions with multiple tunneling channels. To our knowledge no theory has been formulated for the MQT in multigap systems. The theory predicts that the escape rate, i.e., the rate of quantum tunneling, is drastically enhanced compared with that in conventional single-channel systems.In multigap superconductors a collective mode called the Leggett's mode18-20 appears in the low energy region, which is an out-of-phase oscillation mode of the superconducting phases. In Ref.14 a theory for the Josephson effect in superconducting hetero junctions made of a single-gap superconductor and a two-gap one is formulated. In such Josephson junctions, because two kinds of gauge-invariant phase differences can be defined, there are two phase oscillation modes, i.e., the in-phase mode and the out-of-phase one, which correspond, respectively, to the Josephson-plasma and the Josephson-Leggett (JL) mode. In this paper we construct a theory for the MQT in superconducting hetero junctions,...

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Charge transport in normal metal–magnesiumdiboride junctions

Cited by 14 publications

References 20 publications

Observation of Leggett’s Collective Mode in a MultibandMgB2Superconductor

Observation of Leggett’s Collective Mode in a MultibandMgB2Superconductor

Theory of light-induced resonances with collective Higgs and Leggett modes in multiband superconductors

Macroscopic quantum tunneling in multigap superconducting Josephson junctions: Enhancement of escape rate via quantum fluctuations of the Josephson-Leggett mode

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