Hydrogen-like excitons in a high magnetic field

Abstract
A high magnetic field, such that the distance between the Landau levels exceeds the binding energy of an exciton, gives an opportunity to create various new states of matter, i.e., exciton crystal, excitonic molecular complexes, Bose-Einstein condensate of an exciton gas in semiconductors. We found that for the magnetic fields below 4.2. 10⁴T the ground state of hydrogen molecule is the strongly bound singlet state (¹∑_g), for magnetic fields stronger than 3.10⁶T the ground state of the molecule is the strongly bound triplet ( ¹∑_a) , and for magnetic fields between 4.2 .10⁴T and 3.10⁶T symmetry of the ground state is the triplet state (¹∑_u ) , which is characterized by repulsion at intermediate internuclear distances and by weak quadrupole-quadrupole interaction between atoms at large internuclear separation. In this region of magnetic field strength the hydrogen molecule is bound weakly, if at all, the hydrogen behaves like a weakly nonideal Bose gas and can form superfluid phase predicted in earlier works [l , 2]. As was found in recently reported experiments with the uniaxially deformed germanium in a magnetic field, sufficiently strong intensity of the applied magnetic field results in the appearance of a new line in the optical spectrum. The new spectral line in the luminescence spectra may be attributed to the formation of strongly bound biexcitonic molecules in the quantum triplet state. The possibility of the electron-hole liquid formation is also considered.