Electron-electron (e-e) and electron-hole (e-h) interactions are often associated with many exotic phenomena in correlated electron systems. Here, we report an observation of anomalous excitons at 3.75, 4.67, and 6.11 eV at 4.2 K in bulk SrTiO3. Fully supported by ab initio GW Bethe-Salpeter equation calculations, these excitons are due to strong e-h and e-e interactions with different characters: 4.67 and 6.11 eV are resonant excitons and 3.75 eV is a bound Wannier-like exciton with an unexpectedly higher level of delocalization. Measurements and calculations on SrTi1-xNbxO3 for 0.0001≤x≤0.005 further show that the energy and spectral-weight of the excitonic peaks vary as a function of electron doping (x) and temperature, which are attributed to screening effects. Our results show the importance of e-h and e-e interactions yielding to anomalous excitons and thus bring out a new fundamental perspective in SrTiO3.
Anomalous excitons and screenings unveiling strong electronic correlations in SrTi1-x Nbx O3 (0≤x≤0.005) ANOMALOUS EXCITONS and SCREENINGS UNVEILING ... PRANJAL KUMAR GOGOI et al
Trevisanutto P. E.;
2015-01-01
Abstract
Electron-electron (e-e) and electron-hole (e-h) interactions are often associated with many exotic phenomena in correlated electron systems. Here, we report an observation of anomalous excitons at 3.75, 4.67, and 6.11 eV at 4.2 K in bulk SrTiO3. Fully supported by ab initio GW Bethe-Salpeter equation calculations, these excitons are due to strong e-h and e-e interactions with different characters: 4.67 and 6.11 eV are resonant excitons and 3.75 eV is a bound Wannier-like exciton with an unexpectedly higher level of delocalization. Measurements and calculations on SrTi1-xNbxO3 for 0.0001≤x≤0.005 further show that the energy and spectral-weight of the excitonic peaks vary as a function of electron doping (x) and temperature, which are attributed to screening effects. Our results show the importance of e-h and e-e interactions yielding to anomalous excitons and thus bring out a new fundamental perspective in SrTiO3.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
