A Surface-Tailored, Purely Electronic, Mott Metal-to-Insulator Transition
R. G. Moore,1
Jiandi Zhang,2,3
V. B. Nascimento,1
R. Jin,3
Jiandong Guo,1
G.T. Wang,4
Z. Fang,4
D. Mandrus,3
E. W. Plummer1,3
Mott transitions, which are metal-insulator transitions (MITs)
driven by electron-electron interactions, are usually accompanied
in bulk by structural phase transitions. In the layered perovskite
Ca
1.9Sr
0.1RuO
4, such a first-order Mott MIT occurs in the bulk
at a temperature of 154 kelvin on cooling. In contrast, at the
surface, an unusual inherent Mott MIT is observed at 130 kelvin,
also on cooling but without a simultaneous lattice distortion.
The broken translational symmetry at the surface causes a compressional
stress that results in a 150% increase in the buckling of the
Ca/Sr-O surface plane as compared to the bulk. The Ca/Sr ions
are pulled toward the bulk, which stabilizes a phase more amenable
to a Mott insulator ground state than does the bulk structure
and also energetically prohibits the structural transition that
accompanies the bulk MIT.
2 Department of Physics, Florida International University, Miami, FL 33199, USA.
3 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
4 National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China.
