Complementary Approaches to Stress and Strain

Datum: 24.02.2026
Uhrzeit: 10:00 - 12:00
Vortragende(r): Maximilian Pelly
University of St. Andrews (UK)
Ort: MPI CPfS
Raum: Seminarraum 1 + 2

Since the development of high-quality cryogenic stress cells a decade or so ago uniaxial stress has proved an extremely powerful tool for tuning and accessing interesting quantum phases. However, despite significant progress in cell design during the intervening years, these experiments remain incredibly difficult, especially if one wants to go beyond basic transport or bulk thermodynamic measurements. Additionally their uniaxial design fundamentally limits the type of strain modes that can be directly accessed.

I will discuss two complementary techniques that can aid with these issues, starting with our development of an ultra-high-resolution dilatometer. Being the conjugate variable to stress, the evolution of a material's strain contains a lot of information about how observables responds to uniaxial stress, encoded for example in the Maxwell, Clausius–Clapeyron and Ehrenfest relations. Most interesting though are quantum oscillations in strain, which can be used to extract the linear response of Fermi surface pockets to applied stress, something we demonstrate using Sr2RuO4.

This however remains limited to uniaxial modes, but there is no fundamental reason why these should couple the most, or even at all, to the properties we wish to tune. To go further and control internal modes we must turn to chemistry and isovalent doping. If done carefully this allows selective activation of internal strain modes while having minimal effects on other interactions in the crystal. We demonstrate that this can be used for band structure engineering in Sr3Ru2O7, and also hints at possible deeper lattice involvement in many quantum phase transitions, easily missed due to the difficulty in resolving internal modes without careful neutron diffraction.