泓理论坛第五十五期

地点：西安交通大学仲英楼B241 （兴庆校区）

时间：2026年6月30日（周二）下午17:00

主办单位：西安交通大学物理学院

报告人：Prof. Klaus Müller-Dethlefs, University of Manchester

报告主题：A Periodic Many-body Quantum Matter Produced in an Ultra-cold Quantum Degenerate Plasma: Direct Observation of Fractional Elementary Charges

报告简介：

We report the experimental observation of a very striking periodicity in an ultra-cold plasma. A long life-time (>0.3 ms) quantum degenerate molecular Rydberg plasma is generated in the high-density region of a pulsed supersonic jet expansion by two-colour resonant excitation of nitric oxide (10%) in neon (10bar) into the high-n Rydberg threshold region close to the ionization limit. Experimentally, two synchronous UV laser pulses produce the plasma about a mm away from the jet nozzle. For plasma densities of > 10¹⁶ cm^–3 reached in our experiments the electrons should become quantum degenerate, i.e. the electron de Broglie wavelength becomes larger than the Wigner-Seitz radius a relevant to describe the mean distance between the particles. A time-of-flight (ToF) mass spectrometer collinearly with the jet expansion is used to analyse the plasma by applying two successive high-voltage pulses of 3.6 kV with a 0.2 s gap. A very astonishing periodic ToF distribution of 12 very sharp peaks is observed! This observed progression follows fractions derived from the so-called Jain Series describing the filling factors for the Fractional Quantum Hall Effect which is typically observed in solid-state semiconductors close to zero K and in a high magnetic field. An interpretation for the observations presented here is the initial formation of a Wigner-Abrikosov Ion Crystal in the quantum degenerate plasma, i.e. a Solid State! The application of the very fast (10ns) rising and falling high electric field pulses then produces the planar topological bodies which are showing very surprising, but clearly evidenced features of the Jain Series of the Fractional Quantum Hall Effect that one would not necessarily expect to observe in a “gas-phase supersonic jet experiment” at twelve orders of magnitude lower density than solid state.

个人简介：Klaus Muller-Dethlefs now is the Emeritus Professor of the University of Manchester. He established research centers for laser spectroscopy, photochemistry, and photonics at the University of York and the University of Manchester. He was the joint Chair professor of Physics and Chemistry at the University of Manchester. His research fields is about high-excitation-state and non-covalent interactions in laser spectroscopy. He has published more than 120 papers in peer-reviewed journals, with an H-factor of 40, totaling approximately 7,000 citations, including a single paper with up to 1,669 citations and 12 papers each receiving over 100 citations. He has chaired numerous international conferences, including two Gordon Scientific Conferences. He is the academician of the British Physical Society. He also was awarded the 1994 Rudolf-Kaiser Prize for Physicists for his invention of zero-electron kinetic energy spectroscopy (ZEKE spectroscopy) and his contributions to nonlinear laser spectroscopy, and became the first recipient of Canada's Herzberg Memorial Award and Scholarship in 2000–2001. He also served as an editorial board member for internationally renowned journals such as Chemical Physics Letters and Journal of Physics B: Atomic, Molecular and Optical Physics.