title: Two-colour spin noise spectroscopy and fluctuation correlations reveal homogeneous linewidths within quantum-dot ensembles.
abstract: 'Spin noise spectroscopy' is an optical technique for probing electron and hole spin dynamics that is based on detecting their intrinsic fluctuations while in thermal equilibrium. Here we show that fluctuation correlations can be further exploited in multi-probe noise studies to reveal information that in general cannot be accessed by conventional linear optical spectroscopy, such as the underlying homogeneous linewidths of individual constituents within inhomogeneously broadened systems. This is demonstrated in singly charged (In,Ga)As quantum-dot ensembles using two weak probe lasers: When the lasers have similar wavelengths, they probe the same quantum dots in the ensemble and show correlated spin fluctuations. In contrast, mutually detuned probe lasers measure different subsets of quantum dots, giving uncorrelated fluctuations. The noise correlation versus laser detuning directly reveals the quantum dot homogeneous linewidth even in the presence of a strong inhomogeneous broadening. Such noise-based correlation techniques are not limited to semiconductor spin systems, but are applicable to any system with measurable intrinsic fluctuations.
authors.affiliation: National High Magnetic Field Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Luyi
authors.initials: L
authors.lastname: Yang
authors.affiliation: Experimentelle Physik 2, Technische Universität Dortmund, D-44227 Dortmund, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Glasenapp
authors.affiliation: Experimentelle Physik 2, Technische Universität Dortmund, D-44227 Dortmund, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Greilich
authors.affiliation: Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Reuter
authors.affiliation: Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
authors.forename: A D
authors.initials: AD
authors.lastname: Wieck
authors.affiliation: 1] Experimentelle Physik 2, Technische Universität Dortmund, D-44227 Dortmund, Germany [2] Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St Petersburg, Russia.
authors.forename: D R
authors.initials: DR
authors.lastname: Yakovlev
authors.affiliation: 1] Experimentelle Physik 2, Technische Universität Dortmund, D-44227 Dortmund, Germany [2] Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St Petersburg, Russia.
authors.forename: M
authors.initials: M
authors.lastname: Bayer
authors.affiliation: National High Magnetic Field Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Crooker