Photoinduced metastable dd-exciton-driven metal-insulator transitions in quasi-one-dimensional transition metal oxides

Teguh Citra Asmara,Tao Zhu,Caozheng Diao,Florian Biebl,Dongyang Wan,Ping Yang,Angga Dito Fauzi,Benjamin Grimm-Lebsanft,Michael Rübhausen,T Venkatesan,Mark B H Breese,Philipp Lenzen,Andrivo Rusydi,Sören Buchenau,Frank Lichtenberg,Muhammad Avicenna Naradipa,Paolo E Trevisanutto,Pranab Kumar Das

doi:10.1038/s42005-020-00451-w

Abstract

Photoinduced phase transitions in matters have gained tremendous attention over the past few years. However, their ultrashort lifetime makes their study and possible control very challenging. Here, we report on highly anisotropic d-d excitonic excitations yielding photoinduced metal-insulator transitions (MITs) in quasi-one-dimensional metals Sr1-yNbOx using Mueller-Matrix spectroscopic ellipsometry, transient ultraviolet Raman spectroscopy, transient mid-infrared reflectivity and angular-resolved photoemission spectroscopy supported with density functional theory. Interestingly, the MITs are driven by photo-pumping of d-d excitons, causing the metallic a-axis to become insulating while the insulating b- and c-axis concomitantly become a correlated metal. We assign these effects to an interplay between the melting of charge and lattice orderings along the different anisotropic optical axes and Bose-Einstein-like condensation of the photoinduced excitons. The long lifetime in the order of several seconds of the metastable MITs gives greater flexibility to study and manipulate the transient excitonic state for potential applications in exciton-based optoelectronic devices.

Highlights

1234567890():,; Photoinduced phase transitions in matters have gained tremendous attention over the past few years
High-density excitons created by high-intensity photoexcitation can potentially condense into transient Bose–Einstein condensates[10,11,12] (BECs), similar to what has been demonstrated by photoinduced magnon Bose–Einstein condensates10–12 (BECs) transition driven by high-intensity microwave pumping[13]
The d–d exciton pumping is found to drive complementary metal-insulator transitions (MITs) along different optical axes, where the metallic axis switches to become insulating while the insulating axis concomitantly becomes more metallic by rearranging their charge and lattice orderings

Summary

Introduction

1234567890():,; Photoinduced phase transitions in matters have gained tremendous attention over the past few years. The MITs are driven by photo-pumping of d-d excitons, causing the metallic a-axis to become insulating while the insulating b- and c-axis concomitantly become a correlated metal We assign these effects to an interplay between the melting of charge and lattice orderings along the different anisotropic optical axes and Bose-Einstein-like condensation of the photoinduced excitons. The excited state is metastable with an extremely long lifetime of several seconds, caused by the slow recovery of the changes in lattice orderings and possible emergence of BEC-like excitonic phase. This long lifetime gives greater flexibility in manipulating the pumped state for both fundamental research and practical applications

Methods

Results

Conclusion