Quantum-optical spectroscopy of semiconductor nanostructures

• Applicant: Professor Dr. Stephan W. Koch, since 9/2016 (†)
• Subject Area: Theoretical Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2011 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 201125783

• Final Report Year: 2018

Final Report Abstract

We identified and investigated various interesting nonlinear processes in different kinds of semiconductor materials which are caused by extremely short and very strong light pulses in the THz spectral range. These phenomena range from high-harmonic and high-order sideband generation in bulk and monolayer materials to the nonlinear response of a two dimensional electron gas. Such processes are at the heart of ultrashort pulse synthesis, as well as of great interest in the development of lightwave electronics and quantum computing. In detail, we analyzed the polarization dependence of high-harmonic frequency combs emitted from semiconducting GaSe and introduced a conceptually simple model based on our quantum mechanical theory in order to explain the observations and to identify the underlying physical processes. Our study provides direct access to the carrier wave of the emitted high-energy radiation providing valuable inputs for the creation and control of arbitrarily shaped ultrashort pulses. Furthermore, we studied THz driven collisions between electrons and holes in bulk and a monolayer of WSe2. Comparing our microscopic quantum theory with sophisticated experiments, we showed that the high-energy sideband radiation which is emitted during collision events carries information about the material as well as the colliding quasiparticles. On this basis, we introduced the concept of a quasiparticle collider in analogy to large scale particle colliders where the high-energy radiation produced by collisions of ions provides information about the fundamental building blocks of matter. At the same time, the underlying ultrafast coherent wavepacket dynamics are of great interest for the development of lightwave electronics operating at optical clockrates. Furthermore, we demonstrated the concept of lightwave valleytronics where a strong THz field transports optically created valley coherence between two inequivalent energy minima in a monolayer of WSe2. This may serve as the basis for quantum logic operations based on monolayer materials. Moreover, we identified similar capabilities in a THz-induced nonlinear response of Landau quantized electrons in a two-dimensional electron gas. Our research provides promising prospects for the creation and control of attosecond pulses from solids, as well for realizing lightwave electronics and identifies suitable platforms for quantum information processing. A one page feature article was published on 21.05.2018 in the regional daily newspaper Oberhessische Presse, titled "Marburger ebnen Weg zum Quantencomputer". A newspaper article, titled "Rasante Talfahrt" was published in Rhein-Neckar-Zeitung Nr. 148, June 30/July 1, 2018 (http://www.euroscience.net/2018/RNZ20180630.pdf).

Publications

• "High-harmonic generation in solids", Proc. SPIE 9746, 974607-974618 (2016)
  U. Huttner, M. Hohenleutner, F. Langer, O. Schubert, M. Knorr, R. Huber, S. W. Koch, and M. Kira
  
• "Lightwave-driven quasiparticle collisions on a subcycle timescale", Nature 533, 225-229 (2016)
  F. Langer, M. Hohenleutner, C. P. Schmid, C. Poellmann, P. Nagler, T. Korn, C. Schüller, M. S. Sherwin, U. Huttner, J. T. Steiner, S. W. Koch, M. Kira, and R. Huber
  
• „Coherent cyclotron motion beyond Kohn's theorem", Nature Physics 12,119-123 (2016)
  T. Maag, A. Bayer, S. Baierl, M. Hohenleutner, T. Korn, C. Schüller, D. Schuh, D. Bougeard, C. Lange, R. Huber, M. Mootz, J. E. Sipe, S. W. Koch & M. Kira
  
• "Symmetry controlled temporal structure of high-harmonic carrier fields from a bulk crystat'. Nature Photonics 11, 227-231 (2017)
  F. Langer, M. Hohenleutner, U. Huttner, S.W. Koch, M. Kira, and R. Huber
  
• "Ultrahigh off-resonant field effects in semiconductors", Laser & Photonics Reviews 11,1700049 (2017)
  U. Huttner, M. Kira, and S. W. Koch
  
• "Lightwave valleytronics in a monolayer of tungsten diselenide". Nature 557, 76-80 (2018)
  F. Langer, C. P. Schmid, S. Schlauderer, M. Gmitra, J. Fabian, P. Nagler, C. Schüller, T. Korn, P. G. Hawkins, J. T. Steiner, U. Huttner, S. W. Koch, M. Kira, and R. Huber