Strain as a Tuning Parameter of the Superconducting Transition in Nb-doped SrTiO₃

The perovskite semiconductor SrTiO₃ is a quantum paraelectric tunable towards a ferroelectric transition by either ¹⁸O substitution [1] or strain [2] via a quantum critical phase transition and shows a superconducting dome when doped by n-type carriers (Nb or O-deficiency) [3]. The interplay of superconductivity with the unconventional dielectric properties due to the ferroelectric quantum phase transition is a longstanding question [4]. Recent experiments showed that strain can tune T_C [5]. Here we will report on magnetotransport studies on strained single crystals of SrTi_1-xNb_xO₃ in the underdoped, optimally doped and overdoped regimes with a superconducting dome with tensile strain observed when underdoped. This is discussed in relation to the ferroelectric quantum phase transition.

[1] Itoh, M., Wang, R., Appl. Phys. Lett., 76, 221, 2000
[2] Haeni, J. H., et al, Nature, 430, 758, 2004
[3] Lin, X., et al, Phys. Rev. X, 3, 021002, 2013
[4] Edge, J. M., et al, Phys. Rev. Lett. 115, 247002, 2015
[5] Herrera, C., et al, Phys. Rev. Materials, 3, 124801, 2019