Ultrafast Raman thermometry in driven ${\mathrm{YBa}}_{2}{\mathrm{C}\mathrm{u}}_{3}{\mathrm{O}}_{6.48}$

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Ultrafast Raman thermometry in driven ${YBa}_{2} {C u}_{3} O_{6.48}$

T.-H. Chou, M. Först, M. Fechner, M. Henstridge, S. Roy, M. Buzzi, D. Nicoletti, Y. Liu, S. Nakata, B. Keimer, and A. Cavalleri

Phys. Rev. B 109, 195141 – Published 13 May 2024

Abstract

Signatures of photoinduced superconductivity have been reported in cuprate materials subjected to a coherent phonon drive. A “cold” superfluid was extracted from the transient Terahertz conductivity and was seen to coexist with “hot” uncondensed quasiparticles, a hallmark of a driven-dissipative system of which the interplay between coherent and incoherent responses is not well understood. Here, time resolved spontaneous Raman scattering was used to probe the lattice temperature in the photoinduced superconducting state of ${YBa}_{2} {C u}_{3} O_{6.48}$ . An increase in lattice temperature of up to 140 K was observed by measuring the time dependent Raman scattering intensity of an undriven “spectator” phonon mode. This value is consistent with the estimated increase in quasiparticle temperature measured under the same excitation conditions. These temperature changes provide quantitative information on the nature of the driven state and its decay, and may suggest a strategy to optimize this effect.

Received 29 September 2023
Revised 18 April 2024
Accepted 22 April 2024

DOI:https://doi.org/10.1103/PhysRevB.109.195141

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by Max Planck Society.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Lattice dynamics Phonons Superconducting fluctuations Superconducting phase transition

Cuprates High-temperature superconductors

Optical absorption spectroscopy Photoexcitation Raman spectroscopy Terahertz spectroscopy

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

T.-H. Chou ¹, M. Först ¹, M. Fechner¹, M. Henstridge^1,2, S. Roy¹, M. Buzzi¹, D. Nicoletti¹, Y. Liu ³, S. Nakata³, B. Keimer³, and A. Cavalleri^1,4,*

¹Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
²SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
³Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
⁴Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom

^*andrea.cavalleri@mpsd.mpg.de

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Vol. 109, Iss. 19 — 15 May 2024

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Figure 1
Coherent couplings in optically driven ${YBa}_{2} {Cu}_{3} O_{6.48}$ . (a) Schematic of time-resolved terahertz spectroscopy. The midinfrared pump pulse (yellow) resonantly drives infrared-active c-axis apical oxygen phonons in ${YBa}_{2} {Cu}_{3} O_{6.48}$ . Single-cycle terahertz probe pulses (slate gray) were reflected from the sample and detected by phase-sensitive electro-optic sampling. (b) Imaginary part of the c-axis optical conductivity $σ_{2} (ω)$ , measured in ${YBa}_{2} {Cu}_{3} O_{6.48}$ at $T = 100$ K. Gray line and colored circles show the equilibrium and transient $σ_{2} (ω)$ , respectively. The latter was calculated from the data in Ref. [11] with two different models, one based on a linear (blue) and one based on a square root (light green) dependence of the photoinduced response on the pump fluence [12, 13]. (c) Schematic of time-resolved optical spectroscopy. The pump pulse (yellow) is the same as in (a). Near-infrared probe pulses (gray) were detected in reflection geometry. Gray and red arrows represent reflectivity changes at the fundamental frequency $(Δ R)$ and intensity changes of second harmonic generation $Δ I_{SHG}$ , respectively. (d) $Δ R$ (gray) shows an oscillatory response at the Raman phonon frequencies. These data were reproduced from Ref. [16] Fig. 1 after subtraction of a slowly varying background. $Δ I_{SHG}$ shows instead coherent oscillations of the driven infrared-active phonons (orange) and parametrically amplified intrabilayer and interbilayer Josephson plasma polaritons (red). These data were reproduced from Ref. [16] Fig. 2, having applied Fourier transform band pass filters with frequency windows of 0-5, 12-17, and 17-22 THz. (e) Frequency-momentum diagram showing the dispersion curves of driven infrared phonons (orange), Josephson plasmons (light red), and Raman phonons (light gray). The dark gray arrow shows the coupling pathway of stimulated ionic Raman processes between the driven phonons and Raman phonons. The dark red arrows indicate instead the three-mode mixing process between driven phonons and Josephson plasmons.
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Figure 2
Incoherent couplings in optically driven ${YBa}_{2} {C u}_{3} O_{6.48}$ . (a) Left panel: Frequency-momentum diagram with the dispersion curves of resonantly driven infrared phonons (orange), and incoherent Raman phonons at 10.5, 13.5, and 15 THz [18, 19] (light gray). The red gradient background represents the electron distribution above the Fermi energy, which is at zero frequency in this diagram. The wiggling arrows indicate the incoherent energy transfer to Raman phonons (dark gray) and quasiparticles (dark red). Right panel: Electron density of states eDOS (gray) and population $n$ (E) (red). The former was obtained by ab initio calculations, while the latter was calculated by multiplying the eDOS with a Fermi-Dirac distribution at T = 100 K. (b) Real part of the $c$ -axis optical conductivity, $σ_{1}$ (ω), of ${YBa}_{2} {C u}_{3} O_{6.48}$ measured at time delays of $t = - 3$ , 0, and +11 ps. In each panel, gray line and colored circles represent the equilibrium and transient $σ_{1}$ (ω) at T = 100 K, respectively. The latter was calculated from the data of Ref. [11] with two different models, one based on a linear dependence (red) and another one based on a square root dependence (purple) of the photoinduced response on the pump fluence [12, 13]. (c) Equivalent quasiparticle temperature as a function of time delay (colored circles), determined from the integrated spectral weight $\int_{0.6 THz}^{2.25 THz} σ_{1} (ω) d ω$ (see right axis). Red and purple circles refer to the two models introduced in (b) with the same color coding. Full lines are fits with an error function and an exponential decay.
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Figure 3
(a) Schematic of time-resolved spontaneous Raman spectroscopy. The pump (yellow) is the same as in Fig. 1. 405-nm probe pulses (blue) were used for the Raman scattering process. The scattered photons were spectrally analyzed. (b) The Raman spectra were measured at T = 295 K at equilibrium (black) and after photoexcitation (orange). The displayed data were obtained by subtracting background spectra and high-order side peaks from the raw data (see Supplemental Material S2 [32]). The peaks at ±15 THz represent the Stokes (+) and Anti-Stokes (−) responses of the $A_{g}$ symmetry apical oxygen Raman mode. Inset: atomic motions along the $c$ -axis apical oxygen Raman-active mode coordinates. (c) Zero-fluence phonon temperatures as a function of time delay. These data were measured at cryostat base temperatures of 295 K (upper) and 100 K (lower). The dashed red lines were obtained from heating calculation (see Supplemental Material S5 [32]).
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Figure 4
(a) Temperature changes of quasiparticles and Raman phonons as a function of time delay. The solid lines are fits to the data with a model including an error function and an exponential decay. The red and purple circles refer to different models used to extract the terahertz (quasiparticle) response, assuming a linear or a square-root dependence as a function of pump fluence, respectively [12, 13]. (b) Equivalent temperatures of the superfluid as a function of time delay [11]. The blue shaded area highlights the time delay window within which a transient superconductinglike response was observed. The equivalent temperature of the superfluid was determined from $lim_{ω \to 0} ω σ_{2} (ω)$ (values reported on the right axis), using the same models discussed in (a) to calculate the terahertz response, i.e., linear (blue circles) or square-root (light green circles).
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Physical Review B

covering condensed matter and materials physics

Ultrafast Raman thermometry in driven ${YBa}_{2} {C u}_{3} O_{6.48}$

T.-H. Chou, M. Först, M. Fechner, M. Henstridge, S. Roy, M. Buzzi, D. Nicoletti, Y. Liu, S. Nakata, B. Keimer, and A. Cavalleri

Phys. Rev. B 109, 195141 – Published 13 May 2024

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Physical Review B

covering condensed matter and materials physics

Ultrafast Raman thermometry in driven YBa2Cu3O6.48

T.-H. Chou, M. Först, M. Fechner, M. Henstridge, S. Roy, M. Buzzi, D. Nicoletti, Y. Liu, S. Nakata, B. Keimer, and A. Cavalleri

Phys. Rev. B 109, 195141 – Published 13 May 2024

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Ultrafast Raman thermometry in driven ${YBa}_{2} {C u}_{3} O_{6.48}$