Juan Morales

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Altermagnets combine compensated magnetic order with spin-split electronic bands even in the absence of spin–orbit coupling. Since these electronic signatures are tied to the underlying magnetic order, a natural question is what phases can emerge when frustration and quantum fluctuations destabilize it. In this talk, I investigate competing valence-bond states in a spin-1/2 checkerboard Heisenberg model relevant to two-dimensional altermagnetism. Working directly with SU(2) spins, I use a fermionic parton representation and decouple the exchange interactions in the bond-singlet channel. I obtain mean-field solutions within two different unit cells, restricting the search to the sector with vanishing Lagrange multipliers. These solutions include competing dimer and plaquette configurations with degeneracies at the mean-field level. Incorporating Gaussian fluctuations lifts these degeneracies and selects particular valence-bond patterns. Comparing their corrected energies then yields a phase diagram within this set of VBS states, revealing how fluctuations shape the competition between nonmagnetic orders in this model.

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University of Stuttgart
0.03
Contact: Urban Seifert