News Release

Evidence of time-reversal symmetry-protected transport discovered at correlated oxide interfaces

Peer-Reviewed Publication

Science China Press

Evidence of Time-Reversal Symmetry-Protected Transport Discovered at Correlated Oxide Interfaces

image: 

Figure 1: An anomalous quantum oscillation at the ultrahigh-mobility (m+n) unit cell LaAlO₃/SrTiO₃ oxide interface.

view more 

Credit: ©Science China Press

Recently, a research team led by Prof. Guanglei Cheng from the CAS Key Laboratory of Microscale Magnetic Resonance at the University of Science and Technology of China (USTC) achieved a breakthrough in correlated oxide interfaces. For the first time, they discovered an anomalous low-field quantum oscillation at ultraclean LaAlO₃/SrTiO₃ (LAO/STO) oxide interfaces, revealing evidence of an electron subband with an extremely light effective mass (~ 0.03 mₑ). All findings collectively support a scenario of time-reversal symmetry (TRS) protected transport on the quasi-1D ferroelastic domain walls (FDWs) at the interface, driven by a giant Rashba spin-orbit coupling on FDWs. This discovery provides a new platform for designing and engineering novel quantum states. Their findings have been published in National Science Review (NSR), 2025, issue 6, under "Time-Reversal Symmetry Protected Transport at Correlated Oxide Interfaces".

TRS is a fundamental physical symmetry, stating that the physical laws remain invariant when the flow of time is reversed. In materials with strong spin-orbit coupling, such as topological insulators, TRS typically manifests as spin-momentum locking, which effectively suppresses electron backscattering. Although TRS plays a crucial role in topological materials, its integration with electron correlations has remained challenging and could potentially enable exotic quantum states of matter, e.g., the Majorana zero mode.

This idea is particularly appealing in correlated oxide interfaces. On one hand, correlated oxide interfaces usually exhibit rich phenomena like superconductivity and Rashba spin-orbit coupling. On the other hand, the role of TRS in quantum coherent transport behavior at these interfaces remains unclear. Understanding the mechanisms of TRS in correlated oxide interfaces is key to exploring the possibilities of designing and engineering novel quantum states.

The research team introduced a novel growth method utilizing a precisely designed (m+n) modulation doping method to suppress the formation of oxygen vacancies at the interface and successfully grew LAO/STO oxide interfaces with unprecedented mobility.
In these oxygen vacancy-free samples, they observed an anomalous quantum oscillation transport phenomenon at ultralow magnetic fields (~0.3 T) for the first time. The associated carriers have extremely light effective masses, which are rarely reported in STO-based electron systems after extensive study over the past half-century. Additionally, these oscillations exhibited clear aperiodicity and high sensitivity to magnetic fields. Further analysis suggests these oscillations were related to a TRS-protected subband arising from quasi-one-dimensional FDWs in STO. These domain walls exhibited an exceptionally strong Rashba spin-orbit coupling effect, two orders of magnitude higher than conventional correlated oxide interfaces and comparable to typical topological insulator materials.

Moreover, the team discovered that this subband could be effectively tuned by back gate voltage and was closely related to phenomena like multiband transport and superconductivity. They proposed a quantum-corrected multiband model to phenomenologically describe the anomalous back gate modification of this subband. This research provides important experimental evidence for exploring the role of TRS at correlated oxide interfaces and further expands the potential applications of correlated oxide interfaces in quantum engineering.

The first author of this paper is Dr. Mengke Ha from the University of Science and Technology of China (USTC), with Mr. Qing Xiao as the co-first author. Prof. Yang Gao and Prof. Chang-kui Duan supported the development of the theory. Prof. Wei-Tao Liu from Fudan University and Prof. Kecheng Cao from ShanghaiTech University provided experimental characterizations for this study. This research was supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, the CAS Project for Young Scientists in Basic Research, and the Fundamental Research Funds for Central Universities.


Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.