Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 13: Transport: Poster Session

TT 13.46: Poster

Montag, 26. März 2012, 15:00–19:00, Poster B

Strong coupling of paramagnetic spins to a superconducting microwave resonator — •Moritz Greifenstein¹, Christoph Zollitsch¹, Johannes Lotze¹, Fredrik Hocke¹, Rudolf Gross^1,2, Sebastian T.B. Goennenwein¹, and Hans Huebl¹ — ¹Walther-Meissner-Institut (WMI), Garching, Germany — ²Physik-Department, TU München, Garching, Germany

Under application of an external magnetic field, non-interacting electron spins behave as an ensemble of identical two-level-systems with tuneable transition frequency. When such an ensemble collectively interacts with a single mode of an electromagnetic resonator, the entire system can be described as two coupled quantum harmonic oscillators. The criterion for the observation of the so-called strong coupling regime is that the collective coupling strength g exceeds both the loss rate of the resonator κ and of the spin ensemble γ.

In our experiment we realize a coupled spin-photon-system by introducing the spin marker DPPH (2,2-diphenyl-1-picrylhydrazyl) into the mode volume of a superconducting coplanar microwave resonator and investigate the interaction at 2.5, 5.0 and 7.5 GHz. For tuning the resonance, we apply an in-plane magnetic field and observe interaction at around ±90, ±180 and ±270 mT. While the coupling with the fundamental mode and the first harmonic mode of the resonator is identified as weak, the second harmonic shows g=21 MHz, κ=6 MHz and γ=5 MHz, i.e. the strong coupling regime. We further investigate the dependence of g on temperature and on microwave input power. This work is financially supported by DFG via SFB 631.