Abstract
Recent experiments have examined the impact of a magnetic field on ferroquadrupolar orders in the intermetallic Kondo material PrTi$_2$Al$_{20}$. Motivated by this, we use extensive Monte Carlo simulations to study a diamond lattice XY model of non-Kramers pseudospin-$1/2$ Pr$^{3+}$ moments which crucially incorporates three-spin interactions. This model supports a thermal $Z_3$ Potts ordering transition upon cooling from the paramagnetic phase into the ferroquadrupolar phase. An applied magnetic field along the [110] direction leads to a thermal Ising transition out of the quadrupolar ordered phase. A magnetic field along the [001] direction leads to only thermal crossovers, but supports a spinodal transition out of metastable domains which could be strongly pinned by coupling to elastic lattice deformations. We propose noise measurements as a potential probe to "hear" the spinodal transition. Our work highlights the importance of multispin interactions in Kondo materials near the small-to-large Fermi surface transition.
Highlights
The famous Doniach picture of Kondo lattice compounds suggests a scenario for the small-to-large Fermi surface (FS) transition in Kondo lattice materials
A magnetic field along the [001] direction leads to only thermal crossovers, but supports a spinodal transition out of metastable domains which could be strongly pinned by coupling to elastic lattice deformations
Weak Kondo coupling leads to two-spin Ruderman-Kittel-KasuyaYosida (RKKY) interactions which drive rare-earth local moment ordering and a small FS, while strong Kondo coupling leads to the local moments hybridizing with the conduction electrons resulting in a heavy Fermi liquid with a large FS [1,2,3,4,5,6]
Summary
The famous Doniach picture of Kondo lattice compounds suggests a scenario for the small-to-large Fermi surface (FS) transition in Kondo lattice materials. As the Kondo coupling in heavy fermion materials increases, we expect that multispin interactions can arise from higher-order perturbation theory beyond the simple RKKY limit. We argue here that such experiments could potentially probe spinodal transitions out of metastable ground states; such metastable states do exist in the model and may be rendered visible by the strong coupling between the quadrupolar order and elastic lattice deformations. We consider a simple low-energy diamond lattice model for the pseudospin-1/2 non-Kramers doublets, ignoring higher crystal field levels which are split off by a relatively big energy scale ∼50 K, which is much larger than the observed ferroquadrupolar transition temperature. Clocklike anisotropy for pseudospin-1/2 cases must necessarily arise from multisite couplings at the lattice scale We note that this multispin interaction allows for the τz eigenvalue to change in steps of ±3, which cannot arise in any RKKY-type two-spin exchange model. It would be interesting in the future to examine the impact of quantum spin fluctuations in this model
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