alt Hacker NewsIt is an exotic nucleus composed of two protons, one neutron, and one lambda particle (which is a type of hyperon -fermions with three quarks- containing a strange quark). This configuration distinguishes it from regular helium-4, which consists solely of protons and neutrons. The inclusion of a lambda particle introduces "strangeness" into the nucleus, making it a hypernucleus [1].
PS: By exotic here it I use the term as used by particle physicists which just mean not your ordinary stuff discussed in the "popular" working groups. Not the linguistic meaning of the word exotic.
Exotic is defined in the Cambridge Dictionary as:
"unusual and exciting because of coming (or seeming to come) from far away, especially a tropical country"
That doesn't seem too far from the use of it in physics. The "tropical country" part is clearly optional but could be replaced by "especially a special group of scientists".