Polarization-resolved terahertz third-harmonic generation in a single-crystal superconductor NbN: Dominance of the Higgs mode beyond the BCS approximation

Matsunaga, Ryusuke; Tsuji, Naoto; Makise, Kazumasa; Terai, Hirotaka; Aoki, Hideo; Shimano, Ryo

doi:10.1103/physrevb.96.020505

Cited by 110 publications

(244 citation statements)

References 50 publications

Supporting

Mentioning

225

Contrasting

Order By: Relevance

“…These results suggest that the isotropy of the THG signal recently reported in Ref. 6 could be completely recovered once that realistic smearing effects on the LCF response due to disorder are included.…”

Section: Introductionsupporting

confidence: 69%

“…The band dispersion for NbN follows from a tight-binding fit within the manifold of xy, xz, yz d orbitals on the fcc lattice, as suggested in Ref. 6 . By assuming only intra-orbital hopping one has:…”

Section: Derivation Of the Non-linear Responsementioning

confidence: 99%

“…Indeed in this case, considered in Ref. 6 , one can define a single collective phase/density field, removing the polarization dependence of the vertex corrections.…”

Section: Computation Of the Third-harmonic Intensitymentioning

confidence: 99%

“…This term, neglected in the recent analysis of Ref. 6 , does not influence the singular behavior of the non-linear response functions at ω = ∆ 0 , but it suppresses the polarization dependence of the THG, that is further smeared out by a realistic simulation of the finite-width of the pulse. For what concerns the Higgs signal we show that it remains subleading and its polarization dependence depends in general on the form of the pairing interaction.…”

Section: Introductionmentioning

confidence: 98%

See 3 more Smart Citations

Polarization dependence of the third-harmonic generation in multiband superconductors

et al. 2018

View full text Add to dashboard Cite

In a superconductor the third-harmonic generation (THG) of a strong THz pulse is enhanced below Tc by the resonant excitation of lattice-modulated charge fluctuations (LCF), which modulate the response according to the polarization of the field. Here we compute the THG within a multiband model for the prototype NbN superconductor. We show that the non-resonant contribution coming from the instantaneous electronic response and the finite width of the pulse significantly suppress the polarization dependence of the signal, challenging its observation in real systems.

show abstract

Section: Introductionsupporting

confidence: 69%

Section: Derivation Of the Non-linear Responsementioning

confidence: 99%

“…Indeed in this case, considered in Ref. 6 , one can define a single collective phase/density field, removing the polarization dependence of the vertex corrections.…”

Section: Computation Of the Third-harmonic Intensitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

See 2 more Smart Citations

Polarization dependence of the third-harmonic generation in multiband superconductors

et al. 2018

View full text Add to dashboard Cite

show abstract

“…In this context, superconducting (SC) phases have been studied extensively. Both a light-induced enhancement of SC [1][2][3] and the observation of the amplitude Higgs mode [4][5][6] have been reported. Recently, also a related family of ordered states, i.e., excitonic insulators (EIs), has attracted interest [7][8][9][10][11][12].…”

mentioning

confidence: 93%

Photoinduced Enhancement of Excitonic Order

et al. 2017

View full text Add to dashboard Cite

We study the dynamics of excitonic insulators coupled to phonons using the time-dependent mean-field theory. Without phonon couplings, the linear response is given by the damped amplitude oscillations of the order parameter with a frequency equal to the minimum band gap. A phonon coupling to the interband transfer integral induces two types of long-lived collective oscillations of the amplitude, one originating from the phonon dynamics and the other from the phase mode, which becomes massive. We show that, even for small phonon coupling, a photoinduced enhancement of the exciton condensation and the gap can be realized. Using the Anderson pseudospin picture, we argue that the origin of the enhancement is a cooperative effect of the massive phase mode and the Hartree shift induced by the photoexcitation. We also discuss how the enhancement of the order and the collective modes can be observed with time-resolved photoemission spectroscopy. [7][8][9][10][11][12]. An EI state is formed by the macroscopic condensation of electron-hole pairs [13,14], and its theoretical description is analogous to the BCS or Bose-Einstein condensate (BEC) theory for SC. Although the idea of exciton condensation was proposed already in the 1960s [13][14][15], the interest in this topic has been renewed recently by the study of some candidate materials such as 1T-TiSe 2 and Ta 2 NiSe 5 (TNS) [16][17][18][19][20][21]. Their analogy to SC makes the EI an interesting system for nonequilibrium studies. In particular, for TNS, time-and angle-resolved photoemission spectroscopy (trARPES) experiments showed that the direct band gap can be either decreased or increased depending on the pump fluence [11], which was interpreted in terms of a photoinduced enhancement or suppression of excitonic order. A more recent report of the amplitude mode [12] provides further confirmation of an EI state in TNS.So far, the theoretical works on EIs have mainly focused on the equilibrium properties such as the BEC-BCS crossover [22,23], the coupling of the EI to phonons [24][25][26], linear susceptibilities [27][28][29], and the effect of strong interactions and new emergent phases [30][31][32]. In contrast, the nonequilibrium investigation of EIs has just begun [10]. In this work, using TNS as a model system, we clarify two basic effects of the electron-phonon (e-ph) coupling on the dynamics of EIs: (i) the effect on collective modes and (ii) the impact on the excitonic order after

show abstract

Topological Materials for Functional Optoelectronic Devices

Chorsi

Cheng

Zhao

et al. 2022

Adv Funct Materials

Self Cite

View full text Add to dashboard Cite

The recent realization of topology as a mathematical concept in condensed matter systems has shattered Landau's widely accepted classification of phases by spontaneous symmetry breaking as he famously said, "a particular symmetry property exists or does not exist." Topological materials (TMs) such as topological insulators and topological semimetals, are characterized by properties that depend on the topology of the band structure. Such dependence has drastic implications on the optical, electrical, and thermal properties of the material. Fundamental physics of TMs is currently under active research in condensed matter, materials science, and high energy physics. In this review, recent advances in exploiting the unique properties of TMs to realize functional optoelectronic devices are surveyed. Current and future applications that are, or may be, enabled by their unique properties are discussed. Although many theoretical ideas have been proposed over the past decade or so on using TMs in optoelectronic applications, the focus will be on experimentally realized devices.

show abstract

Polarization-resolved terahertz third-harmonic generation in a single-crystal superconductor NbN: Dominance of the Higgs mode beyond the BCS approximation

Cited by 110 publications

References 50 publications

Polarization dependence of the third-harmonic generation in multiband superconductors

Polarization dependence of the third-harmonic generation in multiband superconductors

Photoinduced Enhancement of Excitonic Order

Topological Materials for Functional Optoelectronic Devices

Contact Info

Product

Resources

About