Zeeman splitting and dynamical mass generation in Dirac semimetal ZrTe5

Dirac semimetals have attracted extensive attentions in recent years. It has been theoretically suggested that many-body interactions may drive exotic phase transitions, spontaneously generating a Dirac mass for the nominally massless Dirac electrons. So far, signature of interaction-driven transition has been lacking. In this work, we report high-magnetic-field transport measurements of the Dirac semimetal candidate ZrTe 5 . Owing to the large g factor in ZrTe 5 , the Zeeman splitting can be observed at magnetic field as low as 3 T. Most prominently, high pulsed magnetic field up to 60 T drives the system into the ultra-quantum limit, where we observe abrupt changes in the magnetoresistance, indicating field-induced phase transitions. This is interpreted as an interaction-induced spontaneous mass generation of the Dirac fermions, which bears resemblance to the dynamical mass generation of nucleons in high-energy physics. Our work establishes Dirac semimetals as ideal platforms for investigating emerging correlation effects in topological matters. It has been predicted that the presence of strong electronic correlations may generate new phases in materials with topologically non-trivial band structure. Here, the authors demonstrate the generation of Dirac mass in the correlated Dirac semimetal candidate ZrTe 5 under high magnetic fields.