Mode-Selective Coupling of Coherent Phonons to the Bi2212 Electronic Band Structure

Abstract

Cuprate superconductors host a multitude of low-energy optical phonons. Using time-and angleresolved photoemission spectroscopy, we study coherent phonons in Bi2Sr2Ca0.92Y0.08Cu2O 8+δ . Sub-meV modulations of the electronic band structure are observed at frequencies of 3.94 ± 0.01 and 5.59 ± 0.06 THz. For the dominant mode at 3.94 THz, the amplitude of the band energy oscillation weakly increases as a function of momentum away from the node. Theoretical calculations allow identifying the observed modes as CuO2-derived A1g phonons. The Bi-and Sr-derived A1g modes which dominate Raman spectra in the relevant frequency range are absent in our measurements. This highlights the mode-selectivity for phonons coupled to the near-Fermi-level electrons, which originate from CuO2 planes and dictate thermodynamic properties.

Colloquium: Nonthermal pathways to ultrafast control in quantum materials

“…Time-and angle-resolved photoemission spectroscopy (tr-ARPES) measures changes in the band structure and single-particle spectral function of solids with momentum resolution (Bovensiepen and Kirchmann, 2012;Gedik and Vishik, 2017;Haight et al, 1988;Lv et al, 2019;Nicholson et al, 2018;Petek and Ogawa, 1997;Smallwood et al, 2016;Wegkamp et al, 2014;Zhou et al, 2018). This technique has been used, for example, to study decoherence effects in the excitation process (Höfer et al, 1997;Ogawa et al, 1997;Reutzel et al, 2019), to shed light on the physics of high-temperature superconductors (Avigo et al, 2013;Parham et al, 2017;Smallwood et al, 2012;Yang et al, 2014Yang et al, , 2019, to track the melting and recovery of charge-density wave orders (Hellmann et al, 2010(Hellmann et al, , 2012Perfetti et al, 2006;Rettig et al, 2016;Rohwer et al, 2011;Schmitt et al, 2008;Zong et al, 2019b), to directly probe excitonic states (Cui et al, 2014;Madéo et al, 2020), to measure the relaxation dynamics of photocurrents (Güdde and Höfer, 2021;Reimann et al, 2018) and the coupling between electronic and lattice degrees of freedom (Gerber et al, 2017;Kemper et al, 2017;Na et al, 2019). tr-ARPES also permits the detection of transiently populated topological states (Belopolski et al, 2017;Sobota et al, 2012…”

Expanding the momentum field of view in angle-resolved photoemission systems with hemispherical analyzers

“…In addition to all of the benefits applying in equilibrium, a fixed geometry avoids changes in absorbed excitation density in pumpprobe experiments. 35 Furthermore, the notable increase in effective analyzer transmission due to a larger acceptance range of transverse momenta can be an important aspect when collecting statistics sufficient for high precision studies.…”

Time-resolved ARPES on cuprates: Tracking the low-energy electrodynamics in the time domain

“…In addition to all the investigations listed above, several other alternative applications of TR-ARPES on cuprates have been demonstrated in recent years. These include: (i) tracking of the transient shift of the chemical potential along the nodal direction, and its relation to pump-induced modifications of the superconducting gap [50] and the particle-hole asymmetric pseudogap [51]; (ii) mapping of electronic gaps [52] and the upper Hubbard band [53] in the unoccupied states; and (iii) extraction of the momentum-dependent deformation potential via photoinduced coherent phonons [54].…”