Two-Peak Heat Capacity Accounts for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>R</mml:mi> <mml:mi>ln</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mn>2</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> Entropy and Ground State Access in the Dipole-Octupole Pyrochlore <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>Ce</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> <mml:msub> <mml:mrow> <mml:mtext>Hf</mml:mtext> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">O</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>7</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math>
Bibliographic record
Abstract
Magnetic heat capacity measurements of a high-quality single crystal of the dipole-octupole pyrochlore Ce_{2}Hf_{2}O_{7} down to a temperature of T=0.02 K are reported. These show a two-peaked structure, with a Schottky-like peak at T_{1}∼0.065 K, similar to what is observed in its sister Ce pyrochlores Ce_{2}Zr_{2}O_{7} and Ce_{2}Sn_{2}O_{7}. However, a second sharper peak is observed at T_{2}∼0.025 K, signifying the entrance to the ground state. The ground state appears to have gapped excitations, as even the most abrupt extrapolation to C_{P}=0 at T=0 K fully accounts for the Rln(2) entropy associated with the pseudospin-1/2 doublet for Ce^{3+} in this environment. The ground state could be conventionally ordered, although theory predicts a much larger anomaly in C_{P} at much higher temperatures than the measured T_{2} for expectations from an all-in, all-out ground state of the XYZ Hamiltonian for Ce_{2}Hf_{2}O_{7}. The sharp low-temperature peak could also signify a crossover from a classical spin liquid to a quantum spin liquid (QSL). For both scenarios, comparison of the measured C_{P} with NLC calculations suggests that weak interactions beyond the nearest-neighbor XYZ Hamiltonian become relevant below T∼0.25 K. The diffuse magnetic neutron scattering observed from Ce_{2}Hf_{2}O_{7} at low temperatures between T_{2} and T_{1} resembles that observed from Ce_{2}Zr_{2}O_{7}, which is well established as a π-flux quantum spin ice (QSI). Together with the peak in the heat capacity at T_{2}, this diffuse scattering from Ce_{2}Hf_{2}O_{7} is suggestive of a classical spin liquid regime above T_{2} that is distinct from the zero-entropy quantum ground state below T_{2}.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.013 | 0.009 |
| Meta-epidemiology (narrow) | 0.006 | 0.012 |
| Meta-epidemiology (broad) | 0.003 | 0.012 |
| Bibliometrics | 0.004 | 0.007 |
| Science and technology studies | 0.008 | 0.011 |
| Scholarly communication | 0.012 | 0.010 |
| Open science | 0.016 | 0.014 |
| Research integrity | 0.011 | 0.011 |
| Insufficient payload (model declined to judge) | 0.769 | 0.010 |
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; both teacher heads agree on what is shown here.
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".