You might think that given how basic and ubiquitous photosynthesis is, we’d long ago figured out how it works. Instead, the main parts of the process remain a mystery. New research suggests that one of these phases has striking similarities to exciton capacitors, something physicists have had to go to great lengths to produce in the lab.
Professor David Mazzotti of the University of Chicago heads a lab that uses computer modeling to try to understand the way atoms and molecules interact in important chemical processes. Few of these reactions are as vital and common as photosynthesis, in which plants and algae use energy from sunlight to make sugars and starches.
The process begins with photons hitting the loose electrons in the leaves, allowing both the electron and the “hole” where the charge was to move through the chromophyll (chlorophyll molecule), carrying solar energy. Although this has been known for a long time, Mazziotti and colleagues report that groups of electrons, holes, and holes don’t always move like individuals.
Together, an electron and its hole are known as an exciton, and when viewed together, an electron has different quantum properties than each on its own. An exciton is a boson, for example, while an electron and a hole are both fermions. By modeling the behavior of many excitons, rather than each one individually, the researchers realized how similar their behavior was to a Bose-Einstein condensate, which is sometimes known as the “fifth state of matter” after conventional solids, liquids, gases and plasmas.
Bose-Einstein condensates allow large groups of atoms to exhibit the kind of mind-bending quantum behavior normally seen only at the subatomic level. Not only can they dispense with universal phenomena such as friction, but they can also engage in exotic quantum activities such as combining wave and particle behaviour.
To make Bose-Einstein condensates, scientists need to cool ordered materials to temperatures just above absolute zero, but plants are doing something similar outside your window right now (if it’s daylight). “The photonic light is harvested in a system at room temperature and what’s more, its structure is unstructured — unlike the original amorphous materials and cold temperatures you use to make exciton condensers,” said Anna Skotin, first graduate student on the study. a statement.
The discovery was not made earlier, in part because vegetative excitons are short-lived, and usually quickly recombine. In addition to low temperatures, exciton recombination can be delayed with strong magnetic fields, but of course, plants don’t have these either.
“As far as we know [photosynthesis and exciton condensates] The connection hadn’t been done before, so we found this very compelling and exciting,” Mazziotti said.
Perhaps even more surprisingly, excitons that are colored by chromophores do not become capacitor-like all together. Instead, the spots, which the authors call an “island” shape. However, these islands are not an unrelated curiosity.
A leafy group of excitons. The paper notes that it “may lack some of the properties associated with macroscopic exciton condensation,” but “it is likely to retain many advantages, including efficient transfer of energy.” If so, it would make photosynthesis more efficient, contributing to life’s richness and abundance. Indeed, under ideal conditions, an exciton condensate might double the rate of energy transfer compared to what would otherwise be possible.
Even supercomputers struggle to model the complexity of atomic and subatomic behavior during photosynthesis, so the models become more simplistic than many other scientific scenarios. However, Mazziotti cautions that group behavior is something that should not be ruled out. “We think the local correlation of electrons is essential to capture how nature works in reality,” he said.
The study is open access at PRX Energy
“Devoted student. Bacon advocate. Beer scholar. Troublemaker. Falls down a lot. Typical coffee enthusiast.”