Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

In insulators, the longitudinal resistivity becomes infinitely large at zero temperature. For classical insulators, the Hall conductivity becomes zero at the same time. However, there are special systems, such as two-dimensional quantum Hall insulators, in which a more complex scenario is observed at high magnetic fields. Here, we report experimental evidence for a quasiquantized Hall insulator in the quantum limit of the three-dimensional compound SrSi₂. Our measurements reveal a magnetic-field range, in which the longitudinal resistivity diverges with decreasing temperature, while the Hall conductivity approaches a quasiquantized value that is given only by the conductance quantum and the Fermi wave vector in the field direction. The quasiquantized Hall insulator appears in a magnetic field induced insulating ground state of three-dimensional materials and is deeply rooted in quantum Hall physics.