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Bogdanov, P. V.; Lanzara, Alessandra; Kellar, S. A.; Zhou, X. J.; Lu, E. D.; Zheng, Wenjun; Gu, G. D.; Shimoyama, Jun–ichi; Kishio, K.; Ikeda, Hiroshi; Yoshizaki, Ryozo; Hussain, Zahid; Shen, Z.‐X.

doi:10.1103/physrevlett.85.2581

Cited by 316 publications

(412 citation statements)

References 28 publications

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“…This strong electron-phonon coupling in general gives rise to a renormalization of the band dispersion called a "kink" and an abrupt change of quasiparticle lifetime at an energy related to the phonon frequency, Ω. This idea has been extended to unconventional superconductors, where the mechanism of pairing is unknown, and the coupling of electrons to several collective excitations was reported [4][5][6][7][8][9] . Their origin and relation to pairing is still debated.…”

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confidence: 99%

Strong interaction between electrons and collective excitations in the multiband superconductorMgB2

et al. 2015

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We use a tunable laser ARPES to study the electronic properties of the prototypical multiband BCS superconductor MgB 2 . Our data reveal a strong renormalization of the dispersion (kink) at ∼65 meV, which is caused by coupling of electrons to the E 2g phonon mode. In contrast to cuprates, the 65 meV kink in MgB 2 does not change significantly across T c . More interestingly, we observe strong coupling to a second, lower energy collective mode at binding energy of 10 meV. This excitation vanishes above T c and is likely a signature of the elusive Leggett mode.

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confidence: 99%

Strong interaction between electrons and collective excitations in the multiband superconductorMgB2

et al. 2015

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“…The interpretation of the kinks and other features in electronic spectroscopies [2][3][4][5][6][7] in terms of coupling to collective spin excitations 10 has been hampered by the lack of magnetic spectroscopy data. Most neutron scattering data refer to YBa 2 Cu 3 O 6+x , a compound for which ARPES data are scarce.…”

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confidence: 99%

Two energy scales in the spin excitations of the high-temperature superconductor La2−xSrxCuO4

et al. 2007

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The excitations responsible for producing high-temperature superconductivity in the copper oxides have yet to be identified. Two promising candidates are collective spin excitations and phonons 1 . A recent argument against spin excitations is based on their inability to explain structures observed in electronic spectroscopies such as photoemission 2-5 and optical conductivity 6,7 . Here, we use inelastic neutron scattering to demonstrate that collective spin excitations in optimally doped La 2−x Sr x CuO 4 are more structured than previously thought. The excitations have a two-component structure with a lowfrequency component strongest around 18 meV and a broader component peaking near 40-70 meV. The second component carries most of the spectral weight and its energy matches structures observed in photoemission 2-5 in the range 50-90 meV. Our results demonstrate that collective spin excitations can explain features of electronic spectroscopies and are therefore likely to be strongly coupled to the electron quasiparticles.Since their discovery, considerable progress has been made in understanding the properties of the high-critical-temperature, T c , cuprate superconductors. We know, for example, that the superconductivity involves Cooper pairs, but with d-wave rather than the s-wave pairing of conventional Bardeen-CooperSchrieffer (BCS) superconductors. One outstanding issue is the pairing mechanism itself. For conventional superconductors, identifying the bosonic excitations that strongly couple to the electron quasiparticles played a pivotal role in confirming the phonon-mediated pairing mechanism 8,9 . In the case of the copper oxide superconductors, electronic spectroscopies such as angle-resolved photoemission (ARPES) and infrared optical conductivity measurements 6,7 have revealed structures in the lowenergy electronic excitations, which may reflect coupling to bosonic excitations. ARPES measurements on Bi 2 Sr 2 CaCu 2 O 8 , Bi 2 Sr 2 CuO 6 and La 2−x Sr x CuO 4 have shown rapid changes or 'kinks' in the quasiparticle dispersion, E(k), for energies in the range 50-80 meV (refs 2-5). These features in ARPES have been interpreted in terms of coupling to phonon modes 5 . However, the ARPES measurements do not distinguish between coupling to lattice and spin excitations. Identifying phonons as the strongly coupled bosons is not without its difficulties: we must explain what is special about the phonons in the cuprates; interactions with phonons do not naturally explain other important properties of the cuprates, such as the large linear temperature dependence of the normal-state resistivity at optimal doping and the origin of d-wave symmetry of the superconducting gap itself.The interpretation of the kinks and other features in electronic spectroscopies 2-7 in terms of coupling to collective spin excitations 10 has been hampered by the lack of magnetic spectroscopy data. Most neutron scattering data refer to YBa 2 Cu 3 O 6+x , a compound for which ARPES data are scarce. Although ARPES kinks have also been re...

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“…1a. ARPES results [1] indicate that the nodal quasiparticles have very short lifetimes in the superconducting state, with their spectral functions having linewidths of order k B T , and there is little change [2,3] in this behavior when tuning T through T c . The antinodal quasiparticles are broad and ill-defined above T c [4], but appear to narrow significantly below T c [2,5], forming long-lived states with an energy gap of 30-40 meV.…”

Section: Introductionmentioning

confidence: 99%

“…The purpose of this paper is to discuss quantum phase transitions in the high-T c compounds, and their possible connection to the anomalous quasiparticle properties as seen in ARPES experiments [1][2][3][4][5]. For reasons explained below, we will concentrate on transitions related to the onset (a) of additional is or id xy pairing in d x 2 −y 2 -wave superconductors (leading to damping of nodal quasiparticles) and (b) of antiferromagnetic order (leading to damping of antinodal quasiparticles).…”

Section: Introductionmentioning

confidence: 99%

Quantum Phase Transitions and Collective Modes in d-Wave Superconductors

Vojta

Sachdev

Advances in Solid State Physics

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Abstract. Fluctuations near second-order quantum phase transitions in d-wave superconductors can cause strong damping of fermionic excitations, as observed in photoemission experiments. The damping of the gapless nodal quasiparticles can arise naturally in the quantum-critical region of a transition with an additional spin-singlet, zero momentum order parameter; we argue that the transition to a d x 2 −y 2 + idxy pairing state is the most likely possibility in this category. On the other hand, the gapped antinodal quasiparticles can be strongly damped by the coupling to antiferromagnetic spin fluctuations arising from the proximity to a Neel-ordered state. We review some aspects of the low-energy field theories for both transitions and the corresponding quantum-critical behavior. In addition, we discuss the spectral properties of the collective modes associated with the proximity to a superconductor with d x 2 −y 2 +idxy symmetry, and implications for experiments.

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Evidence for an Energy Scale for Quasiparticle Dispersion inBi2Sr2CaCu2

Cited by 316 publications

References 28 publications

Strong interaction between electrons and collective excitations in the multiband superconductorMgB2

Strong interaction between electrons and collective excitations in the multiband superconductorMgB2

Two energy scales in the spin excitations of the high-temperature superconductor La2−xSrxCuO4

Quantum Phase Transitions and Collective Modes in d-Wave Superconductors

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