Monday, March 29, 2021
Molecular-beam epitaxy (MBE) is renowned for preparing semiconductor heterostructures with high purity, high mobility, and exquisite control of layer thickness at the atomic-layer level. In recent decades it has become the definitive method for the preparation of oxide quantum materials as well. In this talk I will describe the use of MBE to prepare and tune the band structure of ruthenates. The focus of this talk will be on superconductivity in two ruthenates, Sr2RuO4 and RuO2, that includes the effect of biaxial strain on their band structure. The band structure of the strained ruthenate films is revealed by angle-resolved photoemission (ARPES) on pristine as-grown surfaces made possible by a direct ultra-high vacuum connection between MBE and ARPES.[1] Sr2RuO4 is an unconventional superconductor that is extremely sensitive to disorder; it took more than 15 years after the discovery of superconducting Sr2RuO4 single crystals to achieve superconductivity in a single thin film and this result took nearly another decade to reproduce. Using thermodynamics we have identified appropriate conditions for the growth of Sr2RuO4 by MBE,[2] enabling us to synthesize superconducting Sr2RuO4 films reproducibly and with Tc nearly twice as high as other groups in the world.[3] They exhibit quantum oscillations and a mean free path comparable to superconducting Sr2RuO4 single crystals.[4] Our MBE+ARPES studies[5] have enabled theorists to predict ways of raising the superconducting transition of Sr2RuO4 while retaining its (possibly) odd-parity superconducting state. I will also show that RuO2 can be transmuted into a superconductor using epitaxial strain.[6] Our work demonstrates possibilities for utilizing strain engineering as a disorder-free means to manipulate emergent properties and many-body interactions in quantum materials.
https://berkeley.zoom.us/s/98262274858
Meeting ID: 982 6227 4858
Passcode: 279538
SIP: 98262274858@zoomcrc.com
Passcode: 279538
Location: virtual (zoom)
Speaker: Darrell Schlom
Affiliation: Cornell, MBE of Correlated Oxides