Persistent coherence of quantum superpositions in an optimally doped cuprate revealed by 2D spectroscopy

Abstract

Understanding of the precise mechanisms of high-temperature superconductivity is elusive. In particular, in order to solve the puzzle of the pairing mechanism, it is important to understand the detailed nature of the excitations at energies around the superconducting gap. While measurements of the dynamics of excited electronic populations have been able to give some insight, they have largely neglected the intricate dynamics of quantum coherence. Here, we apply multidimensional coherent spectroscopy for the first time to a prototypical cuprate and report unprecedented coherent dynamics persisting for ∼500 fs, originating directly from the quantum superposition of optically excited states separated by 20 -60 meV. These results reveal the correlation between high and low energy excitations, and indicate that the interplay between many-body states on different energy scales conserves phase coherence. In revealing these dynamics we demonstrate that multidimensional coherent spectroscopy can address electronic correlations and interrogate many-body quantum systems in unprecedented ways.

Observing Multiexciton Correlations in Colloidal Semiconductor Quantum Dots via Multiple-Quantum Two-Dimensional Fluorescence Spectroscopy

“…Since multiexcitonic states strongly dictate the nonlinear optical response of quantum dots, coherent two-dimensional (2D) spectroscopy is an excellent tool to study them. , Coherent 2D spectroscopy disentangles the nonlinear response over several frequency axes. Thus, 2D spectroscopy reveals correlation functions with high spectral and high temporal resolution, being further ideally suited to probe coherent superpositions of single excitons. − Coherent 2D spectroscopy was previously applied to colloidal quantum dot systems by detecting coherent third-order nonlinear signals, which correlate the single-exciton states of the system to each other. − ,,− This method enables one to probe multiexciton states indirectly by resolving the transitions from single-exciton states to the respective multiexciton states. Conceptually, this is similar to transient absorption spectroscopy, however with the advantage of an additional spectrally resolved pump axis .…”

Towards Intense THz Spectroscopy on Water: Characterization of Optical Rectification by GaP, OH1, and DSTMS at OPA Wavelengths

“…Future experimental developments should aim both at scaling up the pump fluence without damaging these fragile organic crystals, as well as extending the frequency bandwidth of the detection apparatus without losing dynamical range. Pulse-shaping techniques [89,141] controlling the radiation wavefront [71,94] and/or the spatiotemporal chirp [65] of the laser beams could possibly be optimized to broaden the THz spectrum.…”

Direct and ultrafast probing of quantum many-body interactions through coherent two-dimensional spectroscopy: From weak- to strong-interaction regimes

“…Coherent multidimensional, especially 2D, spectroscopy has been widely used to study electronic excitation (exciton) and vibration dynamics in molecular and semiconductor systems [22][23][24][25][26][27][28][29][30]. More recently, intersubband electronic excitations in quantum wells [31], carrier dynamics in graphene [32], spin-wave [33] and fractional excitations [34,35] in magnetic materials, marginal Fermi glass [36], and high-temperature superconductors [37] have been studied. In coherent 2D spectroscopy, a sequence of three laser pulses is used to excite the system, and the subsequent coherent light emission induced by the polarization of the system is measured.…”