The elastocaloric effect in correlated electron systems

In recent years there has been a surge of interest in the elastic properties of strongly interacting electron materials, in which the strong electron correlations are almost always accompanied by a strong electron-lattice coupling. Tuning the lattice by externally applied stress has been shown to be a highly effective way of introducing controlled modifications to the electronic structure [1], with profound effects on collective many-body states such as superconductivity [2] or electronic liquid crystals [3]. 

For any material whose entropy depends on the strain that it experiences, there will be an elastocaloric signal: an adiabatic change of strain will be accompanied by a change in temperature. If this can be measured sufficiently precisely, the data can be used to identify phase changes and obtain thermodynamic information of profound importance to the understanding of quantum criticality [4]. 

As a result of very recent studies conducted in our Institute, we have realised that elastocaloric measurements supported by finite element simulations will be hugely important both in their own right [5], complementing heat-capacity data [6] and in combination with spectroscopic experiments. Obtaining simultaneous spectroscopic and thermodynamic information from the same sample is no longer a dream but a concrete possibility.  In this project you will work with us to unlock the full potential of this exciting new technique, a taste of which can be seen in this on-line conference talk:


[1] V. Sunko, E. Abarca Morales, I. Marković, M.E. Barber, D. Milosavljević, F. Mazzola, D.A. Sokolov, N. Kikugawa, C. Cacho, P. Dudin, H. Rosner, C.W. Hicks, P.D.C. King, and A.P. Mackenzie
Direct observation of a uniaxial stress-driven Lifshitz transition in Sr2RuO4
npj Quantum Materials 4, 46 (2019)
[2] A. Steppke, L. Zhao, M.E. Barber, T. Scaffidi, F. Jerzembeck, H. Rosner, A.S. Gibbs, Y. Maeno, S.H. Simon, A.P. Mackenzie, C.W. Hicks
Strong peak in Tc of Sr2RuO4 under uniaxial pressure
Science 355, aaf9398 (2017)
[3] J.-H. Chu, H.-H. Kuo, J.G. Analytis, I.R. Fisher
Divergent Nematic Susceptibility in an Iron Arsenide Superconductor
Science 337, 710 (2012)
[4] M.S. Ikeda, J.A.W. Straquadine, A.T. Hristov, T. Worasaran, J.C. Palmstrom, M. Sorensen, P. Walmsley, and I.R. Fisher
AC elastocaloric effect as a probe for thermodynamic signatures of continuous phase transitions
Rev. Sci. Inst. 90, 083902 (2019)
[5] Y. S. Li, M. Garst, J. Schmalian, S. Ghosh, N. Kikugawa, D. A. Sokolov, C. W. Hicks, F. Jerzembeck, M. S. Ikeda, Z. H. Hu, B. J. Ramshaw, A. W. Rost, M. Nicklas, and A. P. Mackenzie
Elastocaloric determination of the phase diagram of Sr2RuO4
Nature 607, 276 (2022).
[6] Y.-S. Li, N. Kikugawa, D.A. Sokolov, F. Jerzembeck, A.S. Gibbs, Y. Maeno, C.W. Hicks, J. Schmalian, M. Nicklas, and A.P. Mackenzie
High-Sensitivity Heat-Capacity Measurements on Sr2RuO4 under Uniaxial Pressure
PNAS 118, e2020492118 (2021)
[7] Y.-S. Li, R. Borth, C.W. Hicks, A.P. Mackenzie, and M. Nicklas
Heat-capacity measurements under uniaxial pressure using a piezo-driven device
Rev. Sci. Instr. 91, 103903 (2020)

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