Electrons, when excited and manipulated, emit light across various energy levels. This light allows scientists to explore phenomena beyond the capabilities of conventional microscopes, revealing the intricate structures of molecules and driving advancements in fields like drug development and computer chip manufacturing. Large facilities like synchrotrons and linear accelerators harness this power, but their size and cost limit accessibility. A new study published in Nature Photonics suggests a revolutionary alternative: quasiparticles.
These quasiparticles, essentially groups of electrons behaving as a single unit, could potentially serve as compact, powerful light sources, democratizing access to cutting-edge research tools. The research team, led by physicists at the Instituto Superior Técnico in Portugal, proposes that these quasiparticles can generate coherent light comparable to that of large free electron lasers, but within smaller laboratory settings.
The key lies in the collective behavior of electrons within the quasiparticle. While no individual electron exceeds the speed of light, the features within the group can, as explained by John Palastro, a physicist at the University of Rochester and co-author of the study. This seemingly paradoxical behavior doesn’t violate any laws of physics, but rather exploits the collective dynamics of the electron group.
An aerial photo of LCLS, a two-mile-long linear accelerator at SLAC National Accelerator Laboratory.An aerial view of the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory. This two-mile-long facility represents the current state-of-the-art in linear accelerator technology. Image Credit: SLAC National Accelerator Laboratory
Current large-scale linear accelerators, such as the recently upgraded LCLS-II at SLAC National Accelerator Laboratory, achieve remarkable brightness by precisely controlling the movement of electrons using powerful magnets. These accelerators generate incredibly bright X-ray pulses, enabling scientists to observe phenomena at unprecedented detail. However, this level of control requires massive infrastructure and significant resources.
The researchers’ approach with quasiparticles offers a different paradigm. Instead of requiring every electron to move in perfect unison, as in a traditional accelerator, the collective behavior of the quasiparticle generates the desired light emission. Bernardo Malaca, lead author of the study, explains that while no single electron undulates, the quasiparticle as a whole produces an “undulator-like spectrum,” mimicking the effect of traditional undulators in large accelerators.
This collective behavior is likened to the “Mexican wave” in a sports stadium. While no individual moves laterally, the sequential rising and sitting creates the illusion of a wave traversing the stadium, potentially faster than any single person could run. Similarly, the collective dynamics of the quasiparticle can exhibit “superluminal” effects, meaning features of the wave appear to travel faster than light, although no individual particle does.
This superluminal behavior, while counterintuitive, is a real phenomenon with measurable effects. The researchers emphasize that the quasiparticle’s effective speed is dependent on the wavelengths involved, with faster-than-light effects occurring when the wavelengths are larger than the quasiparticle itself.
The potential of quasiparticles lies in their ability to generate bright, coherent light without the stringent requirements of large-scale facilities. This could pave the way for “table-top” light sources, enabling researchers to conduct experiments on-site, eliminating the need for access to limited and expensive national facilities.
This breakthrough research offers a glimpse into a future where powerful light sources become more widely available, accelerating scientific discovery and innovation across various fields. The team’s simulations, run on supercomputers provided by the European High Performance Computing Joint Undertaking (EuroHPC JU), demonstrate the feasibility of this approach, suggesting that quasiparticle-based light sources could become a reality in the near future.
