Exciton nature of plasma phase transition in warm dense fluid hydrogen

Abstract: The transition of a warm dense fluid hydrogen from insulator to a conducting state at pressures of the order of 20-300 GPa and temperatures of 1000-5000 K has been the subject of active scientific research over the past few decades. The use of various experimental methods has not yet led to obtaining reliable consistent results, and despite numerous attempts, theoretical methods have not yet been able to explain the existing discrepancies, as well as the microscopic nature of the mechanism for the transition of hydrogen fluid to a conducting state. In this work, we have discovered a key mechanism of the transition associated with formation and dissociation of exciton pairs, which allows to explain several stages of the transition of hydrogen from molecular state to plasma. This mechanism is able to give quantitative description of several experimental results as well as to resolve the discrepancies between different experimental studies.