Bibliographic record
Abstract
In heavy fermion materials, the interplay between conduction electrons and localized moments can yield a variety of exotic phases of matter. This includes non-Fermi liquids, magnetism, unconventional superconductivity, and quantum spin liquids. Recent experiments on rare earth metallic compounds such as \ce{Pr(Ti,V)2Al20} and \ce{Ce3Pd20Si6} have revealed rich phase diagrams. For the case of \ce{Pr(Ti,V)2Al20}, the phase diagram exhibits non-Fermi liquid behaviour, and multipolar order. In \ce{Ce3Pd20Si6}, dipolar and quadrupolar ordering has been observed, along with quantum phase transitions between these phases. At each transition the size of the Fermi surface appears to change sharply at each critical point. Common to both of these systems are multipolar local moments, arising from spin orbit coupling and crystal field effects. These moments hybridize with conduction electrons in highly anisotropic ways, leading to unconventional Kondo interactions, enabling the formation of the aforementioned exotic states. In this thesis, we will study the multipolar Kondo impurity problem and the local approximation of the corresponding Kondo lattice problem to uncover properties of of non-Fermi liquid and multipolar ordered states related to \ce{Pr(Ti,V)2Al20} and \ce{Ce3Pd20Si6}. We will construct simple symmetry allowed models, and then apply renormalization group techniques to extract the essential physics. In the case of \ce{Pr(Ti,V)2Al20}, we find various non-Fermi liquid phases, with resistivity $\rho \sim T^{\Delta}$ and heat capacity $C_V\sim T^{2\Delta}$, with $\Delta = 1/2,1/3,1/5$ taking various values, depending on actual microscopic parameters. We also find a quantum phase transition into a quadrupolar and octupolar ordered states, and compute the critical exponents for susceptibilities at the transition. For \ce{Ce3Pd20Si6}, we find two quantum phase transitions, as one goes between a coexisting dipolar/quadrupolar order, pure quadrupolar order, and a paramagnetic metal. At both transitions the Fermi surface jumps dramatically in size, consistent with recent experiments on the system. Overall, these works advance our understanding of the Kondo effect in multipolar heavy fermion compounds, and present new avenues for further study in an exciting class of materials.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".