Light‐Induced Mott‐Insulator‐to‐Metal Phase Transition in Ultrathin Intermediate‐Spin Ferromagnetic Perovskite Ruthenates

Abstract

Light control of emergent quantum phenomena is a widely used external stimulus for quantum materials. Generally, perovskite strontium ruthenate SrRuO3 has an itinerant ferromagnetism with a low‐spin state. However, the phase of intermediate‐spin (IS) ferromagnetic metallic state has never been seen. Here, by means of UV‐light irradiation, a photocarrier‐doping‐induced Mott‐insulator‐to‐metal phase transition is shown in a few atomic layers of perovskite IS ferromagnetic SrRuO3−δ. This new metastable IS metallic phase can be reversibly regulated due to the convenient photocharge transfer from SrTiO3 substrates to SrRuO3−δ ultrathin films. These dynamical mean‐field theory calculations further verify such photoinduced electronic phase transformation, owing to oxygen vacancies and orbital reconstruction. The optical manipulation of charge‐transfer finesse is an alternative pathway toward discovering novel metastable phases in strongly correlated systems and facilitates potential light‐controlled device applications in optoelectronics and spintronics.

Strain- and Oxygen-Modulated Anomalous Hall Effect in the SrRuO3/Sr3Al2O6 Heterostructure

“… Therefore, the in situ oxygen annealing enhances the domain I-dominated Hall signal, forming a considerable competition of two domains (domain I and domain II) as well as the appearance of a hump-like anomalous Hall signal. Similar oxygen vacancy-induced two domains, which can be reversibly manipulated by the external electric field and light illumination, has been observed in the previous studies. , Therefore, we claim that the hump-like AHE is mainly related to the oxygen vacancy and strain-modulated domain I and domain II, which is closely bonded to the nontrivial band structure of SRO.…”

“…Similar oxygen vacancy-induced two domains, which can be reversibly manipulated by the external electric field and light illumination, has been observed in the previous studies. 65,66 Therefore, we claim that the hump-like AHE is mainly related to the oxygen vacancy and strain-modulated domain I and domain II, which is closely bonded to the nontrivial band structure of SRO.…”

Perspectives: Light Control of Magnetism and Device Development

“…Liu et al, found that ultraviolet (UV) light exposure can initiate a reversible transition from a Mott insulator to a metallic state in a few atomic layers of intermediate-spin (IS) ferromagnetic strontium ruthenate (SrRuO 3−δ ), as shown in Figure d and Figure e. The process involves photocarrier doping, which suggests that light stimulation can be used to achieve room-temperature ferromagnetism and potentially other quantum phases, like unconventional superconductivity .…”

Nanoelectronics Using Metal–Insulator Transition

“…In the condensed matter system, various types of DOF, including spin, lattice electron, and orbital, interact and compete (Figure 4a), which consequently results in the Mott insulator being susceptible to external stimuli. Among various functionalities in the strongly correlated oxides (Figure 4b), the MIT behaviors are triggered by external perturbations such as light, [55,56] electric field, [57][58][59] temperature, [60,61] and lattice strain (Figure 4c). [62,63] It means that Mott insulators can exhibit MIT behaviors in response to various types of external stimuli, making them applicable in diverse and multifunctional nanoelectronics.…”