Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 72: Poster Session: Correlated Electrons
TT 72.94: Poster
Mittwoch, 14. März 2018, 15:00–19:00, Poster B
Non-linear optical response in SrCuO2 — •Philipp Warzanowski1, Eva Benckiser2, Dalila Bounoua3, Paul H. M. van Loosdrecht1, Christian Hess4, and Markus Grüninger1 — 1II. Physikalisches Institut, Universität zu Köln — 2Max Planck Institute for Solid State Research, Stuttgart — 3ICMMO-Université Paris Sud — 4Leibniz-Institute for Solid State and Materials Research, IFW-Dresden
SrCuO2 is regarded as a model system realizing a 1D S=1/2 antiferromagnetic Heisenberg chain with a charge-transfer gap of about 1.6 eV and a large exchange constant of J>0.2 eV. Optical spectroscopy allows us to study spinons by means of phonon-assisted absorption. We find J=225 meV, in good agreement with neutron scattering
results [1]. At low temperatures, the optical data reveal an additional non-linear absorption feature around 0.8 eV which originates from photoexcited states and depends on the incident light intensity. From time-resolved measurements we observe the temporal dynamics for the saturation and relaxation of this feature in the order of seconds to minutes. Above 160 K, this feature vanishes. Based on a three-level scheme, we describe the intensity dependence and time dependence in terms of rate equations. Similar findings in LaSrAlO4 by Demsar et al. [2] suggest a scenario of excited carriers trapped in long-lived states related to oxygen vacancies.
I. A. Zaliznyak et al., Phys. Rev. Lett. 93, 087202 (2004)
J. Demsar et al., Phys. Rev. B 76, 054304 (2007)