Altermagnetic phases and phase transitions in Lieb-$5$ Hubbard model

TL;DR

This paper investigates altermagnetic phases in a Lieb-5 Hubbard model, revealing phase transitions from nonmagnetic to altermagnetic metallic states driven by electron interactions and hopping parameters, with stability against spin-orbit coupling and temperature.

Contribution

It introduces and characterizes altermagnetic order in the Lieb-5 Hubbard model, identifying new metallic phases and phase transitions driven by Hubbard interactions and hopping terms.

Findings

Identification of a unique altermagnetic isolated band metal phase (AMIM).

Discovery of an intermediate altermagnetic metallic phase (AMM).

Demonstration of phase stability against spin-orbit coupling and temperature.

Abstract

The emergence of altermagnetism, the collinear magnetic phase characterized by momentum-dependent spin-split bands but zero net magnetization, has fundamentally reshaped the classification of magnetic order. We propose an altermagnetic (AM) order in a repulsive Hubbard model on the Lieb-$5$ lattice. Considering only nearest-neighbor hoppings within the lattice, we show a phase transition from the nonmagnetic to a unique AM isolated band metal phase (AMIM), allowing clear identification of spin-split states. Additionally, the AM metallic phase (AMM) is also shown to appear as an intermediate phase during the transition from the normal metal to the AMIM in the presence of the diagonal hopping within each unit cell of the Lieb-$5$ lattice. The manifestation of distinct AM phases and the phase transitions, driven by Hubbard interaction and hopping integrals, have been explored in terms of spin-resolved band structure, spectral function, and the behavior of the AM order parameter. The stability of these AM phases against the spin-orbit coupling and temperature is also established.