The phase diagram of (111) SrTiO3/LaAlO3 interfaces

The two dimensional electron liquid formed at the (111) interface between SrTiO3 and LaAlO3 is
a laboratory for studying electronic properties in tunable correlated hexagonal systems.
Symmetry changes imposed by the interface and by various structural transitions in the bulk can
affect the electronic properties at the interface. In addition, this system can be smoothly tuned
from the superconductor deep into the insulator regime.
The normal state properties of the (111) LaAlO3/SrTiO3 interface are indicative of contributions
from electron-type and hole-type charge carriers. The latter are also consistent with the polar
structure of this interface. Upon applying gate voltage to add electrons, a band with a higherspin
state gets populated, resulting in a six-fold anisotropic magnetoresistance [1].
Superconductivity is observed in a dome-shaped region in the carrier density – temperature

phase diagram. The upper critical field is strongly anisotropic and exceeds the Clogston-
Chandrasekhar limit. This suggests strong spin-orbit interaction so. Surprisingly, so is also

nonmonotonic as a function of gate voltage as found both from analysis of the superconducting
properties and of the weak antilocalization measurements [2].
Finally, in the depleted region we can probe the highly insulating regime, where the sheet
resistance is significantly larger than the quantum one. Despite the large resistance, the
interface exhibits the sharp increase in resistance under applied magnetic field characteristic of
a superconductor to insulator transition. By use of electrostatic gating and magnetic fields, the
sample is tuned from the metallic region, where supeconductivity is fully manifested, deep into
the insulating state. Through examination of the field dependence of the sheet resistance and
comparison of the response to fields in different orientations we show that vortex-like
fluctuations are responsible for the transition in this material and that these fluctuations persist
deep into the insulating state [3].

[1] P.K. Rout, I. Agireen, E. Maniv, M. Goldstein, Y. Dagan Physical Review B 95 (24), 241107
[2] P.K. Rout, E. Maniv, Y. Dagan, arXiv:1706.01717 (Accepted in Phys. Rev. Lett.)
[3] M. Mograbi et al. To be published somewhere but not in Nature.