Time-Resolved Photoexcitation of the Superconducting Two-Gap State in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow><mml:mi mathvariant="normal">M</mml:mi><mml:mi mathvariant="normal">g</mml:mi><mml:mi mathvariant="normal">B</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:math>Thin Films

Xu, Ying; Khafizov, Marat; Satrapinsky, L.; Kúš, P.; Plecenı́k, A.; Sobolewski, Roman

doi:10.1103/physrevlett.91.197004

Cited by 54 publications

(43 citation statements)

References 24 publications

(9 reference statements)

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“…Since the electron-phonon interaction time in MgB 2 was observed to be approximately 1-2 ps, 9 thin MgB 2 films were suggested for HEB mixers. 10 With a critical temperature, T c of 39 K in bulk films as thin as 20 nm with a T c of 20-22 K have been fabricated using Molecular Beam Epitaxy (MBE).…”

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confidence: 99%

Low noise terahertz MgB2 hot-electron bolometer mixers with an 11 GHz bandwidth

Novoselov

Cherednichenko

2017

Applied Physics Letters

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Terahertz (THz) hot-electron bolometer mixers reach a unique combination of low noise, wide noise bandwidth, and high operation temperature when 6 nm thick superconducting MgB2 films are used. We obtained a noise bandwidth of 11 GHz with a minimum receiver noise temperature of 930 K with a 1.63 THz Local Oscillator (LO), and a 5 K operation temperature. At 15 K and 20 K, the noise temperature is 1100 K and 1600 K, respectively. From 0.69 THz to 1.63 THz, the receiver noise increases by only 12%. Device current-voltage characteristics are identical when pumped with LOs from 0.69 THz up to 2.56 THz, and match well with IVs at elevated temperatures. Therefore, the effect of the THz waves on the mixer is totally thermal, due to absorption in the π conduction band of MgB2.

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confidence: 99%

Low noise terahertz MgB2 hot-electron bolometer mixers with an 11 GHz bandwidth

Novoselov

Cherednichenko

2017

Applied Physics Letters

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“…Of the various spectroscopic approaches, optical time-resolved spectroscopy is a unique method that probes phase ordering via nonequilibrium carrier relaxation. [1][2][3] For multiple ground systems, a selective evaluation of the individual states can be realized by determining the difference between the associated relaxation components with high time resolution. [4][5][6] Selective enhancement of the signals from the individual states has also been demonstrated by changing the resonant conditions for the higher excited states.…”

Section: Introductionmentioning

confidence: 99%

Optical selection of a multiple phase order in the charge density wave condensateo-TaS3using a spectrally resolved nonequilibrium measurement

et al. 2009

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We investigate the spectrally resolved transient reflectivity changes ⌬R͑T , , ͒ in the charge density wave ͑CDW͒ conductor o-TaS 3 . A distinct near-infrared resonance in this compound emphasizes the characteristic ⌬R͑͒ resonances, and allows a selection of coexisting CDW phases with different nonequilibrium carrier dynamics. Furthermore, the spectrally resolved ⌬R͑͒ characterizes the collective oscillations associated with the individual states. We believe that this demonstration paves the way for the optical selection of the multiphase order that plays an important role in various macroscopic quantum systems.

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“…We do not intend to speculate on the reason for difference in the two reported [10,11] OPOP experiments, since it should be related to the quality of the prepared thin films and/or the character of the substrates. In any case, however, the difference in the relaxation dynamics of the order of 10 2 between OPOP [10] and OPTP [11] for a sudden T-dependent effect at T c , which should be related to the microscopic mechanism of superconductivity, strongly indicates that over the time period between the pump and probe pulses, different microscopic processes might be detected.…”

Section: Introductionmentioning

confidence: 99%

“…In any case, however, the difference in the relaxation dynamics of the order of 10 2 between OPOP [10] and OPTP [11] for a sudden T-dependent effect at T c , which should be related to the microscopic mechanism of superconductivity, strongly indicates that over the time period between the pump and probe pulses, different microscopic processes might be detected.…”

Section: Introductionmentioning

confidence: 99%

“…In this respect, the relaxation dynamics of MgB 2 (as a thin film on different substrates) derived from optical pump-optical probe (OPOP) and optical pump-terahertz probe (OPTP) experiments, seem to be rather confusing. In OPOP experiments [10] (where the relative change of reflectance is detected), the relaxation dynamics at high temperatures (T ~ 70-300 K) are dominated by single-exponential fast sub-ps decay, with  r1  160 fs. Below 70 K, besides  r1 dynamics, the next relaxation process  r2 on the ps time scale is identified.…”

Section: Introductionmentioning

confidence: 99%

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Microscopic insight into the pump–probe relaxation dynamics of superconductors: Model study of MgB₂ relaxation within nonlinear response theory

Baňacký

Szöcs

2016

Physica Status Solidi (b)

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ReceivedHere we present a quantum-statistical formulation of relaxation dynamics of superconductors related to pump-probe (PP) spectroscopy. The method is based on the perturbation expansion of the non-equilibrium density matrix for calculation of multi-time correlation functions, and the corresponding response function. As a model for our study, the high-temperature superconductor MgB 2 has been selected. Knowledge of the electronic structure and of the corresponding Eliashberg function of electron-phonon (EP) interactions enabled us to distinguish nonequilibrium processes in a sequence of interactions with laser pulses on a microscopic level. Temperature-dependent relaxation dynamics as a function of delay time between the pump and probe pulses have been derived. We have shown that an abrupt increase of the relaxation time at T c is the direct consequence of sudden changes in the character of EP coupling in transition from an adiabatic to a stabilized superconducting anti-adiabatic state, as it predicts the anti-adiabatic theory of electron-vibration interactions. The BCS model, which is based on adiabatic character of EP coupling, is basically unable to reflect the enormous sudden increase of the relaxation time at T c . Differences in the optical pump-optical probe and the optical pump-terahertz probe settings of PP relaxation dynamics are discussed within diagrammatic perturbation theory.Keywords: pump-probe spectroscopy; relaxation dynamics of superconductors; electron-phonon coupling; theory of superconductivity; anti-adiabatic theory of superconductivity IntroductionPump-probe (PP) spectroscopy, a method of nonlinear optics, is an important experimental tool in the study of ultrafast relaxation dynamics of excited states in condensed matter systems [1,2]. The interpretation of experimental results relies on various types of phenomenological equations of motion for the relaxation of "hot electrons" and/or high-energy phonons in coupling to bosonic degrees of freedom [3][4][5][6][7]. The assumption of quasi-equilibrium, which is often behind these methods, is discussed in [8], where the authors present an analytic solution of excited state relaxation dynamics within the Boltzmann kinetic equation, the method of which deals with electrons and phonons out of equilibrium.In general, however, phenomenological treatments not only ignore nonlinear aspects of processes running in PP experiments, but ignore also the microscopic character of nonequilibrium states -coherences and/or populations, which can evolve in the studied system over a sequence of different time periods via the interaction of matter with the incident fields. In these circumstances, mainly in the case of superconductors, it is difficult to disclose the relationship between the derived relaxation parameters, i.e. relaxation times, or electron-phonon (EP) coupling constants (), and the microscopic mechanism of the superconducting state transition. The theory of high-temperature superconductors (e.g. cuprates, pnictides) is far from being settled,...

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Time-Resolved Photoexcitation of the Superconducting Two-Gap State inMgB2Thin Films

Cited by 54 publications

References 24 publications

Low noise terahertz MgB2 hot-electron bolometer mixers with an 11 GHz bandwidth

Low noise terahertz MgB2 hot-electron bolometer mixers with an 11 GHz bandwidth

Optical selection of a multiple phase order in the charge density wave condensateo-TaS3using a spectrally resolved nonequilibrium measurement

Microscopic insight into the pump–probe relaxation dynamics of superconductors: Model study of MgB₂ relaxation within nonlinear response theory

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Time-Resolved Photoexcitation of the Superconducting Two-Gap State inMgB2Thin Films

Cited by 54 publications

References 24 publications

Low noise terahertz MgB2 hot-electron bolometer mixers with an 11 GHz bandwidth

Low noise terahertz MgB2 hot-electron bolometer mixers with an 11 GHz bandwidth

Optical selection of a multiple phase order in the charge density wave condensateo-TaS3using a spectrally resolved nonequilibrium measurement

Microscopic insight into the pump–probe relaxation dynamics of superconductors: Model study of MgB2 relaxation within nonlinear response theory

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Microscopic insight into the pump–probe relaxation dynamics of superconductors: Model study of MgB₂ relaxation within nonlinear response theory