Robust Excitonic‐Insulating States in Cu‐Substituted Ta2NiSe5. Issue 12 (27th March 2023)

• Record Type: Journal Article
• Authors: Song, Junseong; Jung, Eilho; Cho, Byeong Wook; Song, Bumsub; Kim, Jae Woo; Kim, Hyeonbeom; Kim, Ki Kang; Son, Byoungchul; Lee, Jouhahn; Hwang, Jungseek; Lee, Young Hee
• Is Part Of: Advanced materials interfaces. Volume 10:Issue 12(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-03-27
• Subjects: charge doping -- electrical transport -- excitonic insulator -- optical conductivity -- semiconductor; Materials science -- Periodicals; 620.11
• DOI: 10.1002/admi.202300010
• Languages: English
• ISSNs: 2196-7350

Abstract

Abstract: Excitonic insulators exhibit intriguing quantum phases that further attract numerous interests in engineering the electrical and optical properties of Ta2 NiSe5 . However, tuning the electronic properties such as spin‐orbit coupling strength and orbital repulsion via pressure in Ta2 NiSe5 are always accompanied with electron‐hole pair breaking, which is a bottleneck for further applications. Here, the robust excitonic‐insulating states invariant with electron‐doping concentrations in Ta2 NiSe5 are demonstrated. The electron doping is conducted by substituting Cu into Ni site (Ta2 Ni1‐ x Cu x Se5 ). The majority carrier of pristine sample is a hole‐type and is converted to electron‐type with a doping concentration over x = 0.01, whose carrier density can be controlled by varying the Cu concentration. The excitonic transition temperature ( T c ) does not significantly alter with electron‐doping concentrations, which is stark contrast with the declining T c as the hole‐type dopant of Fe or Co increases. The optical conductivity data also demonstrate the invariant excitonic‐insulating states in Cu‐doped Ta2 NiSe5 . The findings of invariant excitonic‐insulating states in n ‐type Cu‐substituted Ta2 NiSe5 can be utilized for further electronic device applications by using excitons. Abstract : Here, the robust excitonic‐insulating state in electron‐doped Ta2 NiSe5 excitonic insulator is discovered. By substituting Cu on Ni site, electrons are injected into the Ta2 NiSe5 system and by performing electrical transport measurements, the robustness of excitonic‐insulating state is confirmed. The optical conductivity measurements clearly visualize the condensation of exciton when the temperature is lowering than the excitonic transition temperature.