Controlling the spin of electrons on ultrashort time scales has been at the heart of fundamental quantum physics as well as future memory and spintronic devices. In a collaboration with our partners from Fritz Haber Institute, Berlin, the University of Bonn, and AMOLF in Amsterdam, we have now discovered a direct pathway to the spin world, reaching unprecedented speed: We exploit the magnetic field component of intense terahertz transients from our high-field source to twist the electron spins in antiferromagnetic nickel oxide and coherently switch on and off a collective spin dance. Unlike visible or near-infrared light, terahertz pulses selectively couple to the spin degree of freedom in essentially all terahertz transparent matter with unprecedented speed, while leaving the system in its electronic ground state. Our findings are expected to enable new possibilities in ultrafast materials science and may inspire novel ideas for future information processing.

The full story has been published in Nature Photonics.

Press releases are provided in English and German.

In a festive ceremony held at University of Konstanz on February 8, 2010, the Rudolf Kaiser Foundation awarded Rupert Huber with the Rudolf Kaiser Prize 2009 for his pioneering contributions to physics on ultrashort time scales. Utilizing highly intense single cycles of light in the infrared and THz regime of the electromagnetic spectrum, the team of the laureate gained fundamentally new insight into the microscopic dynamics of electrons and ions in solids. The findings are equally relevant for basic science as well as applications in next-generation electronics and information processing.
The Rudolf Kaiser Prize is conferred annually to an outstanding young German researcher in the field of experimental physics. With a monetary award of € 35 000, it is one of the most prestigious prizes for young investigators in all natural sciences.

A detailed press release may be found here.

Manipulating photons and electrons on a sub-wavelength scale has enabled exciting avenues in modern quantum physics. We have now managed to extend this level of control also into the fourth dimension – time. Our idea may provide insights into yet unobserved quantum electrodynamic phenomena, such as black hole radiation.
Together with our collaboration partners from Pisa, Trieste, and Paris, we have developed an optical switch based on a semiconductor nanostructure in which extremely strong light–matter coupling can be activated within less than one cycle of light. Femtosecond laser pulses allow us to directly resolve how bare photons morph into hybrid particles of mixed light–matter character.

The full story has been published in Nature.

Please, read the excellent News and Views article by Claire Gmachl and the Editor's Summary for more information.

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Excitons in semiconductors are atom-like pairs of one electron bound to one hole (defect electron). Due to their bosonic nature, excitons are expected to possibly undergo Bose-Einstein condensation (BEC) at low temperatures and high densities. We establish a novel control scheme which may pave the way to systematic laser cooling of excitons analogously to atomic vapors.
In collaboration with our partners from Berlin and Marburg, we use intense multi-terahertz fields of order MV/cm to coherently promote optically dark and dense para excitons in cuprous oxide from the 1s into the 2p state. The experimental results are analyzed with a microscopic many-body theory, identifying up to two internal Rabi cycles.

Read the full story in Physical Review Letters.

E-meet the contributors to this work on these pages.

We have developed a novel high-field terahertz source that allows us to generate what are to our knowledge the most intense phase-locked terahertz transients to date: Peak electric fields of 108 MV/cm and center frequencies continuously tunable from 10 to 72 THz are possible. The table-top facility thus exceeds previous records of THz fields by two orders of magnitude. Free space electro-optic sampling with 8-fs gating pulses from a multi-branch Er:fiber laser allows us to monitor all transients directly in the time domain. The system is used to apply unprecedented electric fields with femtosecond precision and thus opens a new research area of high-field physics of condensed matter.

The full story has been published in Optics Letters.

Rupert Huber and his team have received the European THz Young Investigator Award by the European Optical Society (EOS) for "exciting research performed in the area of terahertz science and technology, namely THz quantum optics". The award ceremenony took place in the framework of the EOS Annual Meeting 2008 in Paris where Dr. Huber presented the latest results of the group in an invited talk. The first prize comes with 1000 € sponsored by Femtolasers.

Read more about the group and recent research efforts in an interview Im Gespräch