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MO: Fachverband Molekülphysik

MO 16: In Memoriam of Hermann Haken (joint session Q/MO)

MO 16.1: Invited Talk

Wednesday, March 12, 2025, 11:00–11:30, HS I PI

Haken's quantum field theoretical understanding of semiconductors and lasers and its present-day impact — •Cun-Zheng Ning — Shenzhen Technology University, China

Prof. Haken was among the earliest few who applied the then-new quantum field theory (QFT) to understand physical processes in semiconductors in the 1950s and lasers in the 1960s. The first decade of his scientific career was devoted to the QFT treatment of non-metallic solids. His long-lasting impacts are reflected by popular terms such as the Haken Potential for excitons and Feynman-Haken Path Integral for calculating the ground-state energy of polarons. The second decade of his career started at Stuttgart. It was devoted to the newly invented laser whose fundamental understanding, as he quickly realized, required extending the known QFT to include noise and dissipation. In the process, he established the full quantum theory for open systems and laid the foundation for Synergetics. His laser theory not only explained or predicted many phenomena in lasers but also provided a general framework for the understanding of problems whenever light-matter interaction is involved. While his first two decades focused on the QFT treatment of semiconductors or light field respectively, a proper description of semiconductor optics requires the QFT treatment of both semiconductors and optical field self-consistently. This task turns out to be as challenging as it is rewarding when Coulomb interaction is included and remains an active field of research today, continued by generations of his students. This talk will cover aspects of Prof Haken's early contributions and some recent progress.

Keywords: semiconductors; lasers; excitons; high order correlation; many-body effects