arXiv subjects

Clifford Hicks

Publications and source records attributed to Clifford Hicks.

4 recordsLinked to original sources

arXiv2023

Constraints on the superconducting state of Sr$_2$RuO$_4$ from elastocaloric measurements

Strontium ruthenate Sr$_2$RuO$_4$ is an unconventional superconductor whose pairing symmetry has not been fully clarified, despite more than two decades of intensive research. Recent NMR Knight shift experiments have rekindled the Sr$_2$RuO$_4$ pairing debate by giving strong evidence against all odd-parity pairing states, including chiral $p$-wave pairing that was for a long time the leading pairing candidate. Here, we exclude additional pairing states by analyzing recent elastocaloric measurements [YS. Li et al., Nature 607, 276--280 (2022)]. To be able to explain the elastocaloric experiment, we find that unconventional even-parity pairings must include either large $d_{x^2 - y^2}$-wave or large $\{d_{xz} \mid d_{yz}\}$-wave admixtures, where the latter possibility arises because of the body-centered point group symmetry. These $\{d_{xz} \mid d_{yz}\}$-wave admixtures take the form of distinctively body-centered-periodic harmonics that have horizontal line nodes. Hence $g_{xy(x^2-y^2)}$-wave and $d_{xy}$-wave pairings are excluded as possible dominant even pairing states.

cond-mat.supr-con↗

arXiv2023

Constraints on a split superconducting transition under uniaxial strain in Sr$_2$RuO$_4$ from scanning SQUID microscopy

More than two decades after the discovery of superconductivity in Sr$_2$RuO$_4$, it is still unclear whether the order parameter has a single component or two degenerate components. For any two-component scenario, application of uniaxial strain is expected to lift the degeneracy, generating two distinct phase transitions. The presence of a second (lower-temperature) transition may be observable by probes that are sensitive to changes in the London penetration depth, $λ$, as a function of temperature, $T$. Here, we use scanning SQUID microscopy combined with a uniaxial strain device to test for a second transition under strain. We only observe a single transition. Within the temperature range where a second transition has been suggested by $μ$SR measurements, we further place a tight upper bound of less than 1% on the change in the zero temperature superfluid density $n_s\proptoλ^{-2}(0)$ due to a second transition, suggesting that such a transition does not occur. These results constrain theories of the order parameter in Sr$_2$RuO$_4$.

cond-mat.supr-con↗

arXiv2022

Tuning the Fermi Liquid Crossover in Sr$_2$RuO$_4$ with Uniaxial Stress

We perform nuclear magnetic resonance (NMR) measurements of the oxygen-17 Knight shifts for Sr$_2$RuO$_4$, while subjected to uniaxial stress applied along [100] direction. The resulting strain is associated with a strong variation of the temperature and magnetic field dependence of the inferred magnetic response. A quasi-particle description based on density-functional theory calculations, supplemented by many-body renormalizations, is found to reproduce our experimental results, and highlights the key role of a van-Hove singularity. The Fermi liquid coherence scale is shown to be tunable by strain, and driven to low values as the associated Lifshitz transition is approached.

cond-mat.str-el↗

arXiv2016

Strain and Vector-Magnetic-Field Tuning of the Anomalous Phase in Sr3Ru2O7

Symmetry is a basic paradigm for analysis of problems in solid state physics, and to controllably break point-group symmetries is a powerful probe of novel forms of order. In this work, we apply two methods, controlled lattice strain and vector magnetic field, to study a well-known correlated electron phase that appears at low temperatures in the layered material Sr3Ru2O7. This phase responds strongly to C4-symmetry-breaking fields, suggesting spontaneous C4 symmetry breaking. However, in this work we find that the data are more easily explained with microscopic coexistence of two orthogonal order parameter components than spontaneous symmetry breaking. The techniques presented in this work will be relevant for other systems where spontaneous C4 symmetry breaking is suspected.

cond-mat.str-el↗