Probing biexciton in monolayer WS₂ through controlled many-body interaction

Abstract

The monolayers of semiconducting transition metal dichalcogenides host strongly bound excitonic complexes and are an excellent platform for exploring many-body physics. Here we demonstrate a controlled kinetic manipulation of the five-particle excitonic complex, the charged biexciton, through a systematic dependence of the biexciton peak on excitation power, gate voltage, and temperature using steady-state and time-resolved photoluminescence (PL). With the help of a combination of the experimental data and a rate equation model, we argue that the binding energy of the charged biexciton is less than the spectral separation of its peak from the neutral exciton. We also note that while the momentum-direct radiative recombination of the neutral exciton is restricted within the light cone, such restriction is relaxed for a charged biexciton recombination due to the presence of near-parallel excited and final states in the momentum space.

Trion-trion annihilation in monolayer WS$_2$

“…With an increase in doping density, the χ 0 peak gradually fades out due to a transfer of its oscillator strength to the negatively charged trion (χ − ) [1,2,[33][34][35] and charged biexciton (β − ), as indicated in Figure 1b. The biexcitonic nature of the β − peak is identified through a super-linear power law [4,8,36] (see Supplementary Material [24] Figure 4). While all the three peaks show a slight blue shift at low positive V g , with an increase in voltage, both the χ − (for V g > 1 V) and β − (for V g > 2.5 V) peaks exhibit a strong redshift (zoomed in Figure 1d).…”

“…Semiconducting monolayers of transition metal dichalcogenides (TMDCs) exhibit strongly bound excitons and other higher-order excitonic complexes [1][2][3][4][5][6][7][8][9]. Under high excitation density, large Coulomb interaction in these sub-nanometer-thick monolayers can lead to a strong interaction among these excitonic complexes [3,[10][11][12][13][14][15].…”

Biexciton-like quartet condensates in an electron-hole liquid

“…In highly-excited CuCl, the condensation of biexcitons were observed [31][32][33]. In the past years, the formation of biexcitons was observed also in transition metal dichalcogenide crystals [34][35][36][37]. Recently, it was reported that biexcitons play a key role for the formation of quantum droplet in photo-excited semiconductors [38].…”

Highly nonlinear biexcitonic photocurrent from ultrafast inter-layer charge transfer

“…[5][6][7][8][9][10][11] The signatures of two (exciton), three (charged exciton or trion), four (biexciton) or five-particle (charged biexciton) states have been extensively probed through several optical spectroscopic techniques. [5][6][7][8][9][10][11][12][13][14][15][16] These many-body states along with their different spin and valley configurations of the constituent particles further lead to a nexus of complex states. 7,17,18 Of particular interest is the large five-particle state -charge biexciton, [5][6][7][8]16 which dominates the optical response of monolayer WS 2 and WSe 2 at relatively higher power density because of their strong nonlinearity due to many-body effect.…”

“…[5][6][7][8][9][10][11][12][13][14][15][16] These many-body states along with their different spin and valley configurations of the constituent particles further lead to a nexus of complex states. 7,17,18 Of particular interest is the large five-particle state -charge biexciton, [5][6][7][8]16 which dominates the optical response of monolayer WS 2 and WSe 2 at relatively higher power density because of their strong nonlinearity due to many-body effect. [5][6][7][8]16 The charged biexciton state also exhibits large gate tunability, [5][6][7][8] electric field induced quantum confined Stark effect, 19 and magnetic field induced splitting.…”