Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 56: Heterostructures, Interfaces and Surfaces II

HL 56.4: Talk

Friday, March 22, 2024, 10:15–10:30, EW 561

Energy states of excitons in finite-size crystals — •Pavel Belov¹, Florian Morawetz¹, Sjard Ole Krüger¹, Stefan Scheel¹, Niklas Scheuler², Patric Rommel², Jörg Main², and Harald Giessen³ — ¹Institut für Physik, Universität Rostock, 18059 Rostock — ²Institut für Theoretische Physik II, Universität Stuttgart, 70569 Stuttgart — ³4th Physics Institute and Research Center SCoPE, Universität Stuttgart, 70569 Stuttgart

Due to quantum confinement, electron-hole pairs in finite-size crystals behave rather differently than in bulk materials: in addition to features of the band structure, in the energy spectrum each quantum-confinement subband produces a proper series of Rydberg levels. The lowest series is attributed to bound electron-hole states, i.e. the exciton states. Moreover, due to the Coulomb coupling of upper subbands to the continuum of lower subbands, electron-hole resonant states appear above the electron-hole scattering threshold. We investigate the dependence of exciton energies on the strength of the quantum confinement. In our study, the energy spectrum of hydrogen-like excitons in Cu₂O-based rectangular quantum wells (QWs) is numerically obtained from the solution of the three-dimensional Schrödinger equation. Various crossings and avoided crossings of energy levels as functions of the QW width are observed and categorized based on the symmetry properties of the exciton wave functions. Particular attention is paid to the limiting cases of narrow and wide QWs. Moreover, energies and linewidths of the electron-hole resonant states are obtained by both the stabilization method and the complex scaling technique.

Keywords: exciton; quantum well; cuprous oxide; confinement; spectrum