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This is a repository copy of Chiral topological photonics with an embedded quantum emitter.

We have used time-resolved scanning Kerr microscopy (TRSKM) and micromagnetic simulations to demonstrate that, when driven by spatially uniform microwave field, the edges of patterned magnetic samples represent both efficient and highly tunable sources of propagating spin waves. The excitation is due to the local enhancement of the resonance frequency induced by the non-uniform dynamic demagnetizing field generated by precessing magnetization aligned with the edges. Our findings represent a crucial step forward in the design of nanoscale spin-wave sources for magnonic architectures, and are also highly relevant to the understanding and interpretation of magnetization dynamics driven by spatially-uniform magnetic fields in patterned magnetic samples.

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Article:Mehrabad, M.J., Foster, A.P. orcid.org/0000-0002-5817-0008, Dost, R. orcid.org/0000-0002-8578-0389 et al. (6 more authors)

We implement the “time-of-flight” (TOF) method for charge carrier mobility (μ) measurements in organic field-effect transistors (OFETs) by applying voltage steps, VS, to OFETs. We use the electric scheme for OFET-TOF introduced by Dunn et al. [Appl. Phys. Lett. 88, 063507 (2006)]. Our investigation of a series of low-threshold poly(triaryl amine) OFETs with different channel lengths, L, suggests that in the OFET-TOF setup, the effective voltage driving carriers across the channel, VTOF, is reduced from VS by a constant voltage that coincides with the OFET’s threshold voltage, VT: VTOF=VS−VT. Under this assumption, TOFs scale as expected from theory with both VS and channel length, L, and the extracted dynamically acquired μ agrees excellently between different samples, and experimental protocols (variation of VS / variation of L). However, “dynamic” μ is higher than the “static” μ conventionally extracted from saturated transfer characteristics, which is also less consistent between samples. Also, we observe that the TOF in OFETs switching from OFF→ON is longer than the TOF in the same OFET switching ON→OFF under the same VS. We rationalize this difference by trap filling in the populated OFET channel.

We present a novel organic field-effect transistor (OFET) characterization scheme that allows for the rapid measurement of both, mobility and threshold voltage, in OFETs. The scheme uses a simple measurement algorithm and is based on cheap, standard electronic components. Results agree excellently with conventional characterization, even for moderate mobilities. The algorithm can be easily automated, which is believed to make it the method of choice where fast response is required, e.g. when OFETs are used as sensors.