Feb 20 – 25, 2017
Fairmont Chateau Lake Louise
Canada/Mountain timezone

Coherent spin physics in OLEDs

Feb 24, 2017, 5:30 PM
36m
Mount Temple A (Fairmont Chateau Lake Louise)

Mount Temple A

Fairmont Chateau Lake Louise

Lake Louise, AB, CANADA
Invited Talk

Speaker

Prof. John Lupton

Description

The ability of some animals to navigate using Earth’s magnetic field is truly perplexing. How can tiny fields of one Gauss induce physiologically relevant reactions when Zeeman shifts are over a million times smaller than kT? The secret appears to lie in field-induced modifications to the effect of hyperfine interactions which become relevant because of the exceptionally long spin coherence times of radical pairs. OLEDs provide an unrivaled proving ground to explore the interplay between spin coherence, spin correlations and external fields through spin-dependent transport and luminescence.

Spin-lattice relaxation in OLEDs is virtually independent of temperature and very slow. Spin dephasing over microseconds can be quantified by pulsed magnetic resonance using conventional echo schemes. Slow spin dephasing enables the direct observation of spin-Rabi flopping of both electron and hole species, which, under suitable resonance conditions, couple with each other to give spin beating. Such signals are, in principle, sensitive down to the single carrier within the OLED, since the measurement reports on spin permutation symmetry rather than on thermal spin polarization. As the sole parameter determining the resonance condition is the g-factor, compact OLED-based low-frequency resonance circuits can be designed to serve as versatile magnetometers. With novel dual singlet-triplet emitters, singlet-triplet oscillations in the radical-pair can now also be probed directly by a color change in emission.

Recent highlights in exploiting coherent singlet-triplet oscillations in OLEDs include the demonstration of direct control of the hyperfine interaction by room-temperature NMR, quantification of the zero-field splitting of intermolecular carrier-pair species, and the direct manifestation of the elusive ac-Zeeman and spin-Dicke effects.

Primary author

Prof. John Lupton

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