Electric current noise in mesoscopic organic semiconductors

TL;DR

This paper shows that nuclear spin fluctuations cause electric current noise in mesoscopic organic semiconductors, revealing the nuclear role in magnetoresistance through spectral analysis influenced by magnetic fields.

Contribution

It demonstrates the connection between nuclear spin fluctuations and current noise in organic semiconductors, providing experimental evidence for nuclei's role in magnetoresistance.

Findings

Current noise spectrum has high and low frequency peaks related to nuclear spin dynamics.

External magnetic and radiofrequency fields alter the noise spectrum shape.

Nuclear spins significantly influence magnetoresistance in organic semiconductors.

Abstract

We demonstrate that nuclear spin fluctuations lead to the electric current noise in the mesoscopic samples of organic semiconductors showing the pronounced magnetoresistance in weak fields. For the bipolaron and electron-hole mechanisms of organic magnetoresistance, the current noise spectrum consists of the high frequency peak related to the nuclear spin precession in the Knight field of the charge carriers and the low frequency peak related to the nuclear spin relaxation. The shape of the spectrum depends on the external magnetic and radiofrequency fields, which allows one to prove the role of nuclei in magnetoresistance experimentally.