Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 19: Spin-controlled Transport I

HL 19.13: Talk

Tuesday, March 23, 2010, 12:45–13:00, H14

Fourth-order frequency correlation spectroscopy at radio-frequencies — •Sebastian Starosielec, Rachel Fainblat, Jörg Rudolph, and Daniel Hägele — AG Spektroskopie der kondensierten Materie, Ruhr-Universität Bochum, Germany

The study of fluctuations, like e.g. Spin Noise Spectroscopy has proved to be a valuable tool for determining intrinsic properties of dynamical systems even in thermal equilibrium. The measurement of higher order correlations, like the “noise of the noise”, promises the access to additional hidden dynamics in the fluctuating signals. We find that higher order correlations are useful for characterizing e.g. the dynamics of a noise-driven nonlinear system or the critical dynamics of systems around a phase transition. The measurement of the covariance of noise intensity at different frequencies is especially appealing, since recent developments in parallel computing on commercially available graphics hardware allow the calculation of two-dimensional correlation spectra of fourth order. Depending on frequency range and resolution, high coverage rates up to real-time processing may be achieved at sample rates up to 180 MHz. As a demonstration, we find strong correlations in frequency modulated radio signals and investigate thermal resistor noise. We envision application to the study of magnetic phase transitions, incoherent spin waves, spin noise in semiconductors, and 1/f noise in various devices. The latter is of high interest since the origin of 1/f noise is still debated, and higher order correlations might distinguish between proposed mechanisms.