Strain-tunable Berry curvature in quasi-two-dimensional chromium telluride

Abstract

Magnetic transition metal chalcogenides form an emerging platform for exploring spin-orbit driven Berry phase phenomena owing to the nontrivial interplay between topology and magnetism. Here we show that the anomalous Hall effect in pristine Cr2Te3 thin films manifests a unique temperature-dependent sign reversal at nonzero magnetization, resulting from the momentum-space Berry curvature as established by first-principles simulations. The sign change is strain tunable, enabled by the sharp and well-defined substrate/film interface in the quasi-two-dimensional Cr2Te3 epitaxial films, revealed by scanning transmission electron microscopy and depth-sensitive polarized neutron reflectometry. This Berry phase effect further introduces hump-shaped Hall peaks in pristine Cr2Te3 near the coercive field during the magnetization switching process, owing to the presence of strain-modulated magnetic layers/domains. The versatile interface tunability of Berry curvature in Cr2Te3 thin films offers new opportunities for topological electronics.

From Stoner to local moment magnetism in atomically thin Cr2Te3

“…Temperature-dependent magnetization of 6 ML sample was measured by superconducting quantum interference device (SQUID) in Supplementary Fig. 2 , showing the same T C as that in literatures 25 , 26 . However, the elusive ferromagnetic signal of 1 ML sample requires a technique of better sensitivity than that provided by conventional SQUID.…”

“…In addition, neutron scattering measurements show −0.14 , 2.78 and 2.53 for Cr 1 , Cr 2 , and Cr 3 , indicating the essential role of the Cr-filled layer in driving the long-range ferromagnetic order in Cr 2 Te 3 . Cr 2 Te 3 thin films have been fabricated by molecular beam epitaxy (MBE) method on silicon and sapphire substrates 25 , 26 , displaying a comparable T C to the single crystals as the film thickness exceeds 4 nm. However, to our best knowledge, there is no exploration of the ferromagnetism in the atomically thin 2D limit.…”

Amorphous Ferromagnetic Metal in van der Waals Materials

“…Moreover, the sign of anomalous Hall resistivity for Cr─Te crystalline alloys changes sensitively depending on their composition [ 32 ] and strain. [ 33 ] This could explain the two anomalous Hall components observed in the heavily irradiated CrGeTe 3 .…”

Gate‐tunable Berry curvature in van der Waals itinerant ferromagnetic Cr7Te8

“…In this regard, the itinerant ferromagnetic (FM) semimetal Cr 1+δ Te 2 , whose band‐crossing based on spin–orbit coupling together with the long‐range magnetic order can lead to a large local Berry curvature in the band structure, 21–24 could serve as an ideal material platform for studying the AHE and other various topological transport phenomena 25,26 . Examples of the Berry curvature and resultant AHE modulation via chemical doping (δ of Cr 1+δ Te 2 ) or strain engineering have been demonstrated in the magnetic semimetal Cr 1+δ Te 2 family 27,28 . However, the AHE modulation by these strategies are usually irreversible, making it difficult to realize switchable control of the AHE and the resultant spintronic applications.…”