Discovery of New Quasiparticles May Expand Understanding of Quantum Solvents


Quasiparticles may hold the key to understanding the quantum scale mechanisms that explain macroscale movements. Image Source: Flickr User: NASA Goddard Photo and Video

Understanding how superfluid helium (liquid helium with zero viscosity) interacts with other molecules has been a formidable challenge. After decades of jumping hurdles, researchers have determined that the rotation of molecules within superfluid helium is due to the formation of quasiparticles called angulons.1 Although this may sound like it has a narrow scope, the implications for this recent discovery stretch well beyond helium, possibly giving us insight into new superfluids or how manufacturers and scientists generally approach solvents. There are many steps to understanding what is occurring at the molecular level in superfluid helium, and as this area of science leaps forward, a comprehensive computer software will be crucial to moving this research into new realms.

Helium, A Noble Gas

Helium gas becomes a liquid at -269℃, and below -271℃, it loses all internal friction and becomes a superfluid. In this state, helium has a host of odd properties—among them the ability to crawl up walls and an aversion to mixing with impurities. To that end, only its hydrodynamic properties were explored until the 1990’s, when researchers discovered that atoms and molecules could be enveloped by superfluid helium should the latter form droplets containing around 1000 helium atoms.

Researchers continued exploring these nanodroplets (or nanocrystals) for molecular spectroscopy, as it allowed investigators to isolate a molecule in a cold environment away from external stimuli. While the helium doesn’t substantially affect spectroscopy, it does disrupt natural molecular rotation; this causes a warping in the moment of inertia value. This rotational shift could be explained using the adiabatic following model, but this model fails to take into account a number of strange problems arising from quantum many-body physics. Therefore, a newer, quantum-inclusive approach is needed. Nanoscale research is hard enough, but the bulk of the initial research on superfluid helium was done with a pen set to paper. This adds unnecessary challenges when researchers wish to re-evaluate findings, as such info may be challenging to find. In addition, analysis needs to start elsewhere, which can be difficult if results are not housed in a comprehensive program that easily integrates with analytical software. Innovative lab software can assist researchers in finding and accounting for these molecular level shifts in motion or spectroscopy.

Quasiparticles: Many-particle Answers

The concept of quasiparticles is used in physics to simplify the description of a many-particle system. By identifying the foundational components of a system—rather than assessing trillions of interactions between molecules one by one—it is easier to get the root of what is occurring. For example, if you were assessing bubbles rising through water, it would be tiresome to analyze the precise position and motion of all the water molecules when you could treat the bubbles as their own particle (a quasiparticle) and assess their actions. This simplifies the system and allows for straightforward analysis, the data for which can be housed and analyzed using computer software. In the case of superfluid helium, enrobed impurities form the angulon quasiparticle. The authors assessed 25 different molecules—including methane, carbon dioxide, and ammonia—and each time, angulons formed. For some of the heavier molecules, the strong-coupling regime—in conjunction with macroscopic deformation of the superfluid—caused renormalization of the molecular moments of inertia and redistribution of the angular momentum between the molecule and the excitations in helium. For lighter species, the change occurs via virtual single-phonon excitations.

As authors seek to prove the above calculations experimentally, perhaps they’ll be able to touch upon a couple other odd behaviors observed in superfluid helium, such as vortices.2  While spraying liquid helium through a fine nozzle into a vacuum chamber in conjunction with an x-ray laser blast, researchers observed that many of the droplets that formed were not spherical. In fact, many appeared drawn-out or wheel-like. Tiny vortices formed, much like nanoscale tornadoes. Currently, there is no explanation for this behavior, but through further experimentation and analysis with modern lab software—taking into account recent discoveries—there may be a solution. Superfluid helium is used alongside a number of superconducting magnets, such as those found in magnetic resonance imaging (MRI) machines. If this concept contributes to wear and tear, we should work to understand the underlying mechanisms and put the uncertainty to rest.

There is an abundance of raw data that may show these peculiar behaviors and attributes on the nanoscale, both in your lab and within literature. BIOVIA Electronic Laboratory Notebooks can help by reducing time spent looking for data by 50%, reducing repeat experiments by 25%, and improving productivity by 25% while removing all non-value added manual activities and errors. In your pursuit of new technological innovations, the clues may be deep within your own data; let BIOVIA alleviate those concerns by housing it all in one space so it can be more cohesively analyzed. Please contact us today to learn more about how our software options can support your lab’s efforts.

  1. “Quasiparticle Approach to Molecules Interacting with Quantum Solvents,” February 27, 2017,
  2.  “Shapes and vorticities of superfluid helium nanodroplets,” August 22, 2014,