Abstract The density distribution of cold exciton clouds generated into a strain‐induced potential well by two‐photon excitation in Cu2O is studied at 2 K. The potential shapes of the double well are examined by two‐photon diagnostics. The motion of the exciton clouds is tracked by time‐resolved luminescence imaging and spectral imaging. We find that an anomalous spike appears on the center of the well in a specific excitation condition, i.e. ΔE = −5.0 meV, where ΔE is the detuning of the two‐photon excitation energy from the orthoexciton level under zero stress. The origin of the spike has been discussed in view of bosonic stimulation of the excitons into the ground state.Abstract The density distribution of cold exciton clouds generated into a strain‐induced potential well by two‐photon excitation in Cu2O is studied at 2 K. The potential shapes of the double well are examined by two‐photon diagnostics. The motion of the exciton clouds is tracked by time‐resolved luminescence imaging and spectral imaging. We find that an anomalous spike appears on the center of the well in a specific excitation condition, i.e. ΔE = −5.0 meV, where ΔE is the detuning of the two‐photon excitation energy from the orthoexciton level under zero stress. The origin of the spike has been discussed in view of bosonic stimulation of the excitons into the ground state.

physica status solidi (b)Jul 21, 200321 citations

Cold Fermion Pairing in Two-Dimensional Harmonic Traps

J. R. Armstrong, Massimo Rontani, Sven AAberg +2 more

Bulletin of the American Physical SocietyMar 19, 20090 citations

Interaction between Rydberg Excitons in Cuprous Oxide Revealed through Resonant Second Harmonic Generation

Andreas Farenbruch, Henje Stolz, Peter Grünwald +5 more

We report experimental and theoretical investigations of interacting excitons of the yellow series in cuprous oxide (Cu $_2$ O) with principal quantum numbers up to by means of second harmonic generation (SHG). Using picosecond pulsed laser excitation up to 10 GW/cm $^2$ peak intensity we observe a pronounced change of the spectra with increasing pump laser intensity: an energetic shift to lower absolute energies and a spectral broadening. The absolute intensities of the spectral lines scale for low powers with the square of the pump power, but saturates at higher powers. At still higher powers the SHG intensity is actually reduced. To explain these results quantitively, we developed a semi-classical theory of resonant SHG where the process of SHG is fully coherent. The excitons are assumed to be bosons interacting by a distance dependent potential giving rise to both the changes in spectral line shape and the saturation by a $\it{Rydberg}$ blockade. The concomitant measurement of two-photon absorption allows to derive quantitative values for the exciton-exciton interaction. While the results agree in order of magnitude with those calculated by state-of-the art atomic-like van der Waals interaction theory, the scaling with principle quantum number is quite different. As a possible screening by an electron-hole plasma created by three-photon absorption into blue and violet band states could be ruled out, our results point toward fundamental differences between excitons and atoms.We report experimental and theoretical investigations of interacting excitons of the yellow series in cuprous oxide (Cu$_2$O) with principal quantum numbers up to by means of second harmonic generation (SHG). Using picosecond pulsed laser excitation up to 10 GW/cm$^2$ peak intensity we observe a pronounced change of the spectra with increasing pump laser intensity: an energetic shift to lower absolute energies and a spectral broadening. The absolute intensities of the spectral lines scale for low powers with the square of the pump power, but saturates at higher powers. At still higher powers the SHG intensity is actually reduced. To explain these results quantitively, we developed a semi-classical theory of resonant SHG where the process of SHG is fully coherent. The excitons are assumed to be bosons interacting by a distance dependent potential giving rise to both the changes in spectral line shape and the saturation by a $\it{Rydberg}$ blockade. The concomitant measurement of two-photon absorption allows to derive quantitative values for the exciton-exciton interaction. While the results agree in order of magnitude with those calculated by state-of-the art atomic-like van der Waals interaction theory, the scaling with principle quantum number is quite different. As a possible screening by an electron-hole plasma created by three-photon absorption into blue and violet band states could be ruled out, our results point toward fundamental differences between excitons and atoms.

cond-mat.mes-hallCross-listedarXiv:2608.08705Aug 11, 20260 citations

We report experimental and theoretical investigations of interacting excitons of the yellow series in cuprous oxide (Cu

_2

O) with principal quantum numbers up to by means of second harmonic generation (SHG). Using picosecond pulsed laser excitation up to 10 GW/cm

^2

peak intensity we observe a pronounced change of the spectra with increasing pump laser intensity: an energetic shift to lower absolute energies and a spectral broadening. The absolute intensities of the spectral lines scale for low powers with the square of the pump power, but saturates at higher powers. At still higher powers the SHG intensity is actually reduced. To explain these results quantitively, we developed a semi-classical theory of resonant SHG where the process of SHG is fully coherent. The excitons are assumed to be bosons interacting by a distance dependent potential giving rise to both the changes in spectral line shape and the saturation by a

\it{Rydberg}

blockade. The concomitant measurement of two-photon absorption allows to derive quantitative values for the exciton-exciton interaction. While the results agree in order of magnitude with those calculated by state-of-the art atomic-like van der Waals interaction theory, the scaling with principle quantum number is quite different. As a possible screening by an electron-hole plasma created by three-photon absorption into blue and violet band states could be ruled out, our results point toward fundamental differences between excitons and atoms.