"Exploration and manipulation of the insulator-metal transition through low-temperature nano-optics" by Alexander McLeod (Columbia University)

Wednesday, March 20, 2019 - 4:00pm to 5:00pm
Condensed Matter Physics Seminar

Exploration and manipulation of the insulator-metal transition through low-temperature nano-optics

Alexander McLeod

Columbia University


Bypassing the diffraction limit of conventional limit of light, near-field microscopy has emerged as an invaluable tool for nanometer-resolved optical investigations of inhomogeneous materials.  Recent instrumental developments have brought this technique to cryogenic temperatures (down to T=20K), a regime where quantum phase transitions such as the insulator-to-metal transition (IMT) can emerge among so-called correlated electron materials.   Using external stimuli including temperature, strain, and even light, here I explore universal phenomenologies and the opportunities for nano-scale control over the IMT among representative correlated electron materials.  I first reveal how spatial morphologies of insulator and metal domains provide clues to short-ranged interactions between coupled order parameters in the rare-earth nickelate NdNiO$_3$, selectively driving the IMT at nanometer scales [1].  On the other hand, I demonstrate how long-ranged interactions with strain produce nano-textured percolation and growth of striped insulator and metal domains in thin films of the “canonical Mott insulator” V$_2$O$_3$ [2].   By tuning the energetic landscape controlling the transition, I demonstrate active manipulation of these textures through nano-imaging of the IMT in layered ruthenate single-crystals under in situ application of uniaxial strain and electrical current.  Lastly, nano-imaging of an epitaxial manganite reveals how a unique combination of coupled order parameters and strain susceptibility create conditions for a metastable IMT both “activated” through optical excitation and “deactivated” through locally applied pressure [3].  These examples highlight the singular capabilities of infrared nano-imaging deployed at cryogenic temperatures, promising expansive opportunities for the future investigation of quantum phase transitions in correlated electron materials.


[1] K.W. Post*, A.S. McLeod*, M. Hepting, M. Bluschke, Y. Wang, G. Cristiani, … & D.N. Basov. Coexisting first- and second-order electronic phase transitions in a correlated oxide. Nature Physics, 1–6. (2018) https://doi.org/10.1038/s41567-018-0201-1.  *These authors contributed equally.

[2] A.S. McLeod, E. Van Heumen, J.G. Ramirez, S. Wang, T. Saerbeck, S. Guenon, … I.K. Schuller, & D.N. Basov. Nanotextured phase coexistence in the correlated insulator V$_2$O$_3$. Nature Physics. (2017) https://doi.org/10.1038/nphys3882

[3] A.S. McLeod*, J.D. Zhang*, M.Q. Gu, … W.B. Wu, J. Rondinelli, R.D. Averitt, & D.N. Basov. Multi-messenger nano-probes of hidden magnetism in a strained manganite.  In submission. (2019) *These authors contributed equally.

4-330 PAB