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Extreme magnetoresistance at high-mobility oxide heterointerfaces with dynamic defect tunability.
D V Christensen1, T S Steegemans2, T D Pomar2
1Department of Energy Conversion and Storage, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark. dechr@dtu.dk.
Nature Communications
|May 18, 2024
Summary
Extreme magnetoresistance (XMR) was observed at the interface of γ-Al2O3/SrTiO3 oxides. This phenomenon arises from electron motion influenced by disorder, not band structure, and can be tuned by dynamic defect engineering.
Area of Science:
- Condensed matter physics
- Materials science
- Solid-state physics
Background:
- Magnetoresistance (MR) quantifies changes in electrical resistance under magnetic fields, offering insights into electronic and magnetic properties.
- Extreme magnetoresistance (XMR) is a significant phenomenon observed in specific materials, characterized by a non-saturating resistance increase (10^3-10^8%) in high magnetic fields.
- XMR is typically associated with materials exhibiting gapless band structures, steep bands, and charge compensation.
Purpose of the Study:
- To investigate the emergence of XMR at the interface between large band-gap oxides γ-Al2O3 and SrTiO3.
- To elucidate the underlying physical mechanisms responsible for XMR in this oxide heterostructure.
- To explore the potential for dynamic defect engineering to tune XMR properties.
Main Methods:
- Magnetotransport measurements were conducted to characterize the electrical resistance under varying magnetic fields and temperatures.
- Microscopic current imaging was employed to visualize charge transport pathways.
- Momentum-resolved band structure calculations provided insights into the electronic properties of the interface.
Main Results:
- A linear XMR of 80,000% at 15 T and 2 K was observed at the γ-Al2O3/SrTiO3 interface.
- The temperature/field phase diagrams showed similarities to known XMR semimetals, despite the dissimilar material environment.
- XMR was attributed to weak disorder-induced squeezed guiding center motion of electrons, rather than band structure features.
- Dynamic self-enhancement of XMR was observed through the redistribution of oxygen vacancies.
Conclusions:
- XMR can occur in oxide interfaces, expanding the range of materials exhibiting this phenomenon.
- The mechanism of XMR in γ-Al2O3/SrTiO3 is primarily governed by electron scattering from disorder, challenging conventional explanations linked to band structure.
- Dynamic defect engineering, specifically oxygen vacancy redistribution, offers a novel pathway for tuning and controlling XMR effects.
