Metal to insulator transition (MIT) is accompanied by huge changes in physical responses by the control and tuning of experimental parameters like doping, pressure, chemical composition, and magnetic field. Here, we study the magnetic field-driven MIT for two pnictides in their elemental form, namely, arsenic and bismuth. At low temperatures, bismuth shows an unusual behavior of a re-entrant insulator–metal transition (IMT) at high fields in addition to a higher temperature MIT at smaller fields. However, arsenic shows the commonly observed single MIT. Shubnikov–de Haas oscillations are observed for both As and Bi below 10 K. Giant magnetoresistance of the order of ∼105 magnetoresistance (MR)% is observed for both crystals at 2 K and the 14 T transverse magnetic field. The unusual Kohler scaling behavior of MR at low temperature indicates the presence of increased carrier density attributed to the melting of excitons. Based on a microscopic model, the microscopic processes underpinning the unusual features of a field-driven MIT and re-entrant IMT, along with the relevance of both excitonic and Bose metal correlations near these incipient instabilities, are qualitatively described in the framework of field-driven excitonic condensate and Das–Doniach preformed pair scenarios in one single picture.
Karn et al. (Thu,) studied this question.