Robust orbital diamagnetism in correlated Dirac fermions

We study orbital diamagnetism at zero temperature in (2 + 1)-dimensional Dirac fermions with a short-range interaction which exhibits a quantum phase transition to a charge density wave (CDW) phase. We introduce orbital magnetic fields into spinless Dirac fermions on the pi-flux square lattice, and analyze them by using infinite density matrix renormalization group. It is found that the diamagnetism remains intact in the Dirac semimetal regime, while it is monotonically suppressed in the CDW regime. Around the quantum critical point of the CDW phase transition, we find a scaling behavior of the diamagnetism characteristic of the chiral Ising universality class. Besides, the scaling analysis implies that the robust orbital diamagnetism at weak magnetic fields in a Dirac semimetal regime would hold not only in our model but also in other interacting Dirac fermion systems as long as scaling regions are wide enough. The scaling behavior may also be regarded as a quantum, magnetic analogue of the critical Casimir effect which has been widely studied for classical phase transitions.

Automated summary

We investigate the orbital diamagnetism at zero temperature in (2 + 1)-dimensional Dirac fermions with a short-range interaction that undergoes a quantum phase transition to a charge density wave (CDW) phase. By introducing orbital magnetic fields into spinless Dirac fermions on the pi-flux square lattice and utilizing the infinite density matrix renormalization group, we observe that diamagnetism is preserved in the Dirac semimetal regime and gradually suppressed in the CDW regime. Near the quantum critical point of the CDW phase transition, we identify a scaling behavior of the diamagnetism characteristic of the chiral Ising universality class. Additionally, the scaling analysis suggests that the robust orbital diamagnetism at weak magnetic fields in a Dirac semimetal regime holds not only in our model but also in other interacting Dirac fermion systems as long as the scaling regions are sufficiently wide. This scaling behavior can also be regarded as a quantum, magnetic equivalent of the critical Casimir effect, which has been extensively studied for classical phase transitions.