Bond Stretching Phonon Softening and Kinks in the Angle-Resolved Photoemission Spectra of Optimally Doped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Bi</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Sr</mml:mi><mml:mn>1.6</mml:mn></mml:msub><mml:msub><mml:mi>La</mml:mi><mml:mn>0.4</mml:mn></mml:msub><mml:msub><mml:mi>Cu</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>6</mml:mn><mml:mo>+</mml:mo><

Graf, J.; d’Astuto, Matteo; Jozwiak, Chris; Garcia, Daniel; Saini, N. L.; Krisch, M.; Ikeuchi, Ken; Baron, Alfred Q. R.; Eisaki, H.; Lanzara, Alessandra

doi:10.1103/physrevlett.100.227002

Cited by 82 publications

(90 citation statements)

References 37 publications

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“…2). The extracted dispersion agrees well with that of the Cu-O bond-stretching phonon measured by non-resonant inelastic X-ray scattering 23 (Supplementary Information). Owing to the high momentum-resolution of our data, Fig.…”

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confidence: 75%

“…phonon softening occurs gradually near Q CDW , unlike the Kohn anomaly due to the reduced lattice symmetry from the CDW, which usually occurs more abruptly in a narrow momentum window. In addition, whereas the width of the phonon self-energy directly measured by inelastic neutron or non-resonant inelastic X-ray scattering is typically a few millielectronvolts 23,24 , the fitted width of peak shown in Fig. 2e progressively broadens near Q CDW and is not resolution limited (∼40 meV), hinting at the existence of additional low-energy excitations.…”

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confidence: 99%

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Dispersive charge density wave excitations in Bi2Sr2CaCu2O8+δ

et al. 2017

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Experimental evidence on high-T c cuprates reveals ubiquitous charge density wave (CDW) modulations 1-10 , which coexist with superconductivity. Although the CDW had been predicted by theory 11-13 , important questions remain about the extent to which the CDW influences lattice and charge degrees of freedom and its characteristics as functions of doping and temperature. These questions are intimately connected to the origin of the CDW and its relation to the mysterious cuprate pseudogap 10,14 . Here, we use ultrahigh-resolution resonant inelastic X-ray scattering to reveal new CDW character in underdoped Bi 2.2 Sr 1.8 Ca 0.8 Dy 0.2 Cu 2 O 8+δ . At low temperature, we observe dispersive excitations from an incommensurate CDW that induces anomalously enhanced phonon intensity, unseen using other techniques. Near the pseudogap temperature T * , the CDW persists, but the associated excitations significantly weaken with an indication of CDW wavevector shift. The dispersive CDW excitations, phonon anomaly, and analysis of the CDW wavevector provide a comprehensive momentumspace picture of complex CDW behaviour and point to a closer relationship with the pseudogap state.With sufficient energy resolution, resonant inelastic X-ray scattering (RIXS) can be an ideal probe for revealing the CDW excitations in cuprates. By tuning the incident photon energy to the Cu L 3 -edge (Fig. 1a), the resonant absorption and emission processes can leave the system in excited final states, which couple to a variety of excitations arising from orbital, spin, charge, and lattice degrees of freedom 15 . Thus, information of these elementary excitations in energy and momentum space can be deduced from analysing the RIXS spectra as functions of the energy loss and the momentum transfer of the photons (Fig. 1a). This is highlighted by the pivotal role that RIXS has recently played in revealing orbital and magnetic excitations in cuprates [16][17][18][19][20] . In addition, RIXS provided the first X-ray scattering evidence for an incommensurate CDW in (Y,Nd)Ba 2 Cu 3 O 6+δ (ref. 4), owing to energy resolution that separated the quasi-elastic CDW signal (bright spot in Fig. 1b, limited by the instrumental resolution ∼130 meV) from other intense higher-energy excitations. Notably this quasi-elastic signal is asymmetric with respect to zero energy loss (Fig. 1c), which indicates the possible existence of additional low-energy excitations near the CDW wavevector (Q CDW ).In this work, we exploit the newly commissioned ultrahighresolution RIXS instrument at the European Synchrotron Radiation Facility to reveal these low-energy excitations near the CDW. We choose the double-layer cuprate Bi 2.2 Sr 1.8 Ca 0.8 Dy 0.2 Cu 2 O 8+δ (Bi2212), whose electronic structure has been extensively studied by surface-sensitive spectroscopy, such as scanning tunnelling microscopy 21 and angle-resolved photoemission 22 , and in which a short-range CDW order was recently reported 7,8 . With improved energy resolution up to 40 meV, we see additional features in the pre...

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Dispersive charge density wave excitations in Bi2Sr2CaCu2O8+δ

et al. 2017

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“…A kink in the electronic dispersions around 70 meV has been reported previously by ARPES and the possibility that the giant phonon anomaly and ARPES features are two sides of the same coin has been raised 11,24 .…”

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confidence: 92%

“…Subsequently, close kinematic relationship between the longitudinal Cu-O bond stretching mode dispersion and renormalization of electronic quasiparticles in Bi 2 Sr 1.6 La 0.4 CuO 6 (Bi2201) indicated that the phonon anomaly may originate from the coupling of phonons to electronic quasiparticles 11 . t − J modelbased calculations also predicted strong coupling of optical phonons to electron-hole excitations 12 .…”

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confidence: 99%

Evidence for a charge collective mode associated with superconductivity in copper oxides from neutron and x-ray scattering measurements of La2−xSrxCuO
Park
¹
,
Fukuda
²
,
Hamann
³

et al. 2014
Phys. Rev. B
45
0
36
2
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In superconducting copper oxides some Cu-O bond-stretching phonons around 70meV show anomalous giant softening and broadening of electronic origin and electronic dispersions have large renormalization kinks near the same energy. These observations suggest that phonon broadening originates from quasiparticle excitations across the Fermi surface and the electronic dispersion kinks originate from coupling to anomalous phonons. We measured the phonon anomaly in underdoped (x=0.05) and overdoped (x=0.20,0.25) La2−xSrxCuO4 by inelastic neutron and x-ray scattering with high resolution. Combining these and previously published data, we found that doping-dependence of the magnitude of the giant phonon anomaly is very different from that of the ARPES kink, i.e. the two phenomena are not connected. We show that these results provide indirect evidence that the phonon anomaly originates from novel collective charge excitations as opposed to interactions with electron-hole pairs. Their amplitude follows the superconducting dome so these charge modes may be important for superconductivity.PACS numbers: 74.25.Kc, 63.20.kd, 74.20.Mn Lattice vibrations in metals can be damped and/or softened by either electronic quasiparticles or collective charge excitations (e.g. plasmons). Giant phonon softening and line broadening of electronic origin of the longitudinal Cu-O bond stretching phonons near half-way to the zone boundary (giant anomaly) was observed in copper oxide high temperature superconductors (HTSCs) 1-11 . It was previously found at superconducting compositions and was also absent in undoped and overdoped nonsuperconducting copper oxides [5][6][7] .First reports interpreted the phonon anomaly as a signature of unit cell doubling 3 followed by a different interpretation 6 in terms of coupling of the phonon to dynamic charge stripes. Subsequently, close kinematic relationship between the longitudinal Cu-O bond stretching mode dispersion and renormalization of electronic quasiparticles in Bi 2 Sr 1.6 La 0.4 CuO 6 (Bi2201) indicated that the phonon anomaly may originate from the coupling of phonons to electronic quasiparticles 11 . t − J modelbased calculations also predicted strong coupling of optical phonons to electron-hole excitations 12 .If phonons couple strongly to electronic quasipaticles, then a BCS-type mechanism of superconductivity may still be valid. Alternatively, the phonon anomaly would arise from a novel collective charge excitations at low energies (at least 70 meV). Then such collective mode may provide the pairing interaction 13-15 .We measured Cu-O bond-stretching phonons in La 2−x Sr x CuO 4 for undoped x=0.00, nonsuperconducting underdoped x=0.05, and superconducting overdoped x=0.20, 0.25. x=0.05 did not show characteristic signatures of the giant phonon anomaly. x=0.20 showed a very strong phonon anomaly, which was dramatically reduced already at x=0.25. On the other hand, the magnitude of the kink in the electronic dispersions gradually decreases from x=0.05 to x=0.30 16,17 . The new data, combine...

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“…or kinks [64][65][66] in the electronic spectrum. In such a strongly coupled material a few phonon quanta have a large effect on the electrons, whereas in a weaker coupled system one needs more quanta to achieve a similar effect.…”

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confidence: 99%

Phonon Driven Floquet Matter

2018

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The effect of electron-phonon coupling in materials can be interpreted as a dressing of the electronic structure by the lattice vibration, leading to vibrational replicas and hybridization of electronic states. In solids a resonantly excited coherent phonon leads to a periodic oscillation of the atomic lattice in a crystal structure bringing the material into a non-equilibrium electronic configuration. Periodically oscillating quantum systems can be understood in terms of Floquet theory, which has a long tradition in the study of semi-classical light-matter interaction. Here, weshow that the concepts of Floquet analysis can be applied to coherent lattice vibrations reflecting the underlying coupling mechanism between electrons and coherent bosonic modes. This coupling leads to phonon-or photon-dressed quasi-particles imprinting specific signatures in the spectrum of the electronic structure. Such dressed electronic states can be detected by time-and angularresolved photoelectron spectroscopy (ARPES) manifesting as sidebands to the equilibrium band structure. Taking graphene as a paradigmatic material with strong electron-phonon interaction and non-trivial topology we show how the phonon-dressed states display an intricate sideband structure revealing the electron-phonon coupling at the Brillouin zone center and topological ordering of the Dirac bands. Most strikingly, we find that the non-equilibrium electronic structure created by coherent dynamical dressing is the same for photon and phonon perturbations. We demonstrate that if time-reversal symmetry is broken by the coherent lattice perturbations a topological phase transition can be induced. This work establishes that the recently demonstrated concept of lightinduced non-equilibrium Floquet phases can also be applied when using coherent phonon modes for the dynamical control of material properties. The present results are generic for bosonic timedependent perturbations, therefore we envision similar phenomena to be observed for example for plasmon, magnon or exciton driven materials.

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Bond Stretching Phonon Softening and Kinks in the Angle-Resolved Photoemission Spectra of Optimally DopedBi2Sr1.6La0.4Cu2O6+<

Cited by 82 publications

References 37 publications

Dispersive charge density wave excitations in Bi2Sr2CaCu2O8+δ

Dispersive charge density wave excitations in Bi2Sr2CaCu2O8+δ

Evidence for a charge collective mode associated with superconductivity in copper oxides from neutron and x-ray scattering measurements of La2−xSrxCuO
Park
¹
,
Fukuda
²
,
Hamann
³

et al. 2014
Phys. Rev. B
45
0
36
2
View full text Add to dashboard Cite

Phonon Driven Floquet Matter

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Bond Stretching Phonon Softening and Kinks in the Angle-Resolved Photoemission Spectra of Optimally DopedBi2Sr1.6La0.4Cu2O6+<

Cited by 82 publications

References 37 publications

Dispersive charge density wave excitations in Bi2Sr2CaCu2O8+δ

Dispersive charge density wave excitations in Bi2Sr2CaCu2O8+δ

Evidence for a charge collective mode associated with superconductivity in copper oxides from neutron and x-ray scattering measurements of La2−xSrxCuOPark1, Fukuda2, Hamann3 et al. 2014Phys. Rev. B450362View full textAdd to dashboardCite

Phonon Driven Floquet Matter

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About

Evidence for a charge collective mode associated with superconductivity in copper oxides from neutron and x-ray scattering measurements of La2−xSrxCuO
Park
¹
,
Fukuda
²
,
Hamann
³

et al. 2014
Phys. Rev. B
45
0
36
2
View full text Add to dashboard Cite