The triplet state (total spin of two electrons S=1) is unbound in the absence of an additional potential or sufficiently strong magnetic field.
Trion states were predicted theoretically in 1958;[1] First time they were observed experimentally in 1993 in CdTe/Cd1−xZnxTe quantum wells by Ronald Cox and co-authors,[2] and later in various other semiconductor structures.
[12][13][14] In such materials, the interaction between the charge carriers is enhanced many times over due to the weakening of the screening [15] An important property of a trion is that its ground state is a singlet.
As a result, in a sufficiently large magnetic field, when all the electrons appear spin-polarised, trions are born under the action of light of only one circular polarization.
[17] In ExCR, an incident photon creates an exciton, which forces an additional electron to transfer between Landau level s. The reverse process is called "shake-up".