Creating macroscopically spin-correlated quantum matter via Kondo cloud condensation
일 시 : 2023년 10월 11일 수요일 17:00
연 사 : 임 현 식 교수 (동국대학교)
장 소 : 자연과학관 B117호
HOST : 정 문 석 교수님
초 록
When a magnetic moment is embedded in a metal, it captures itinerant electrons to form the Kondo cloud with a size of a few micrometres [1]. For a metal where magnetic impurities are reasonably dense that the spacing of their magnetic moments is comparable to the size of the Kondo clouds, the Kondo clouds overlap each other to form a correlated ground state [2]. Here, I present electrical transport and tunneling DOS spectroscopy measurements in a crystalline silicon metal where localized magnetic moments exist. We detect the Kondo effect in the resistivity of the Si metal and an exotic BCS-like pseudogap in the DOS near the Fermi energy. The BCS-like DOS structure is tuned by applying an external magnetic field and transformed into a paramagnetic Coulomb gap. This phenomenon is interpreted as the formation of a correlated ground state of overlapping Kondo clouds (Kondo cloud condensate). I also discuss the interplay between the Kondo condensate and BCS-superconductor in the DOS spectrum of a Si:P-SiO2-Al tunnel junction where some interesting features are observed (i.e., Andreev reflection and particle-hole asymmetry like behavior). Our experimental findings demonstrate the observation of the magnetic version of BCS pair condensation and will be useful for understanding complex Kondo systems.
keywords : Kondo cloud, condensation, strongly correlated quantum matter
[1] I. Borzenets et al., Nature 579, 210 (2020).
[2] H. Im et al., Nature Physics 19, 676 (2023).