@article{DziomShuvaevPimenovetal.2017,
  author    = {Dziom, V. and Shuvaev, A. and Pimenov, A. and Astakhov, G.V. and Ames, C. and Bendias, K. and B{\"o}ttcher, J. and Tkachov, G. and Hankiewicz, E.M. and Br{\"u}ne, C. and Buhmann, H. and Molenkamp, L.W.},
  title     = {Observation of the universal magnetoelectric effect in a 3D topological insulator},
  series = {Nature Communications},
  volume    = {8},
  journal   = {Nature Communications},
  number    = {15197},
  doi       = {10.1038/ncomms15197},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170875},
  year      = {2017},
  abstract  = {The electrodynamics of topological insulators (TIs) is described by modified Maxwell's equations, which contain additional terms that couple an electric field to a magnetization and a magnetic field to a polarization of the medium, such that the coupling coefficient is quantized in odd multiples of α/4π per surface. Here we report on the observation of this so-called topological magnetoelectric effect. We use monochromatic terahertz (THz) spectroscopy of TI structures equipped with a semitransparent gate to selectively address surface states. In high external magnetic fields, we observe a universal Faraday rotation angle equal to the fine structure constant α=e\(^{2}\)/2E\(_{0}\)hc (in SI units) when a linearly polarized THz radiation of a certain frequency passes through the two surfaces of a strained HgTe 3D TI. These experiments give insight into axion electrodynamics of TIs and may potentially be used for a metrological definition of the three basic physical constants.},
  language  = {en}
}
@article{KnorrRudolfNuernberger2013,
  author    = {Knorr, Johannes and Rudolf, Philipp and Nuernberger, Patrick},
  title     = {A comparative study on chirped-pulse upconversion and direct multichannel MCT detection},
  doi       = {10.1364/OE.21.030693},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-111334},
  year      = {2013},
  abstract  = {A comparative study is carried out on two spectroscopic techniques employed to detect ultrafast absorption changes in the mid-infrared spectral range, namely direct multichannel detection via HgCdTe (MCT) photodiode arrays and the newly established technique of chirped-pulse upconversion (CPU). Whereas both methods are meanwhile individually used in a routine manner, we directly juxtapose their applicability in femtosecond pump-probe experiments based on 1 kHz shot-to-shot data acquisition. Additionally, we examine different phase-matching conditions in the CPU scheme for a given mid-infrared spectrum, thereby simultaneously detecting signals which are separated by more than 200 cm-1.},
  language  = {en}
}