Two-Quantum 2D FT Electronic Spectroscopy of Biexcitons in GaAs Quantum Wells

Abstract

The motions of electrons in solids may be highly correlated by strong, long-range Coulomb interactions. Correlated electron-hole pairs (excitons) are accessed spectroscopically through their allowed single-quantum transitions, but higher-order correlations that may strongly influence electronic and optical properties have been far more elusive to study. Here we report direct observation of bound exciton pairs (biexcitons) that provide incisive signatures of four-body correlations among electrons and holes in gallium arsenide (GaAs) quantum wells. Four distinct, mutually coherent, ultrashort optical pulses were used to create coherent exciton states, transform these successively into coherent biexciton states and then new radiative exciton states, and finally to read out the radiated signals, yielding biexciton binding energies through a technique closely analogous to multiple-quantum two-dimensional Fourier transform (2D FT) nuclear magnetic resonance spectroscopy. A measured variation of the biexciton dephasing rate indicated still higher-order correlations.

Intervalley biexcitons and many-body effects in monolayerMoS2

“…Studying intervalley biexcitons could offer a new concept of quasiparticles in solids where valleypseudospin states play significant roles, apart from the usual atom-like orbital and spin states. The large biexciton binding energies in this material offer a promising direction to search for higher-order bound excitons such as triexcitons and the elusive quadexcitons 35,36 as well as their interplay with spin-valley degrees of freedom. We also found that, while two excitons can interact and form a biexciton, the interactions between free excitons in this system reveal a large energy red-shift that obeys a simple power-law behavior with density.…”

Energy transfer pathways in semiconducting carbon nanotubes revealed using two-dimensional white-light spectroscopy

“…There are many different spectrometer designs for collecting 2D spectra 18,[34][35][36][37][38][39][40][41][42] . Our spectrometer design, shown in Supplementary Fig.…”

Parametric projection operator technique for second order non-linear response

“…Developed first in the nuclear magnetic resonance [1] it has been brought to infra red [2][3][4] and later into near infrared and optical domains [5,6]. Since then it yielded new insights into photo-induced dynamics of electronic excited states of small molecules [7], polymers [8], large photosynthetic aggregates [9,10] and even solid state systems [11]. The two-dimensional (2D) Fourier transformed spectrum completely characterizes the third order non-linear response of a molecular ensemble in amplitude and phase [12,13] providing thus, the maximal information accessible in a three pulse experiment.…”