Programming correlated magnetic states with gate-controlled moiré geometry

Abstract

The ability to control the underlying lattice geometry of a system may enable transitions between emergent quantum ground states. Here, we report in-situ gate switching between honeycomb and triangular lattice geometries of an electron many-body Hamiltonian in R-stacked MoTe 2 moiré bilayers, resulting in switchable magnetic exchange interactions. At zero electric field, we observe a correlated ferromagnetic insulator near one hole per moiré unit cell with a widely tunable Curie temperature up to 14K. Applying an electric field switches the system into a half-filled triangular lattice with antiferromagnetic interactions; further doping this layer-polarized superlattice tunes the antiferromagnetic exchange interaction back to ferromagnetic. Our work demonstrates R-stacked MoTe 2 moirés to be a laboratory for engineering correlated states with nontrivial topology.

Ferroic Phases in Two-Dimensional Materials

“…282−284 The tunable ferromagnetism could be achieved by adjusting the twist angle, 285−290 moirécarrier filling, 291,292 and interlayer coupling. 289 The experimental modulation of ferromagnetic/ antiferromagnetic properties has been reported in homolayers such as magic-angle 2L graphene, 287−290 WSe 2 , 293 AAstacked 294 and ABC-stacked 295 MoTe 2 . Additionally, the ferromagnetism also arises in vdW heterojunctions such as 2L graphene integrating with h-BN, 284,296 WSe 2 /WS 2 , 291,292,297 in near-60-degree-twisted (or AB-stacked) MoTe 2 /WSe 2 .…”

“…In the vdW moiré superlattices, the spin alignment is a result of many-body correlations, where the electronic interactions induced gaps and spontaneous symmetry breaking at specific integer fill factors. − The tunable ferromagnetism could be achieved by adjusting the twist angle, − moiré carrier filling, , and interlayer coupling . The experimental modulation of ferromagnetic/antiferromagnetic properties has been reported in homolayers such as magic-angle 2L graphene, − WSe 2 , AA-stacked and ABC-stacked MoTe 2 . Additionally, the ferromagnetism also arises in vdW heterojunctions such as 2L graphene integrating with h-BN, , WSe 2 /WS 2 , ,, in near-60-degree-twisted (or AB-stacked) MoTe 2 /WSe 2 .…”

Raman‐Active Interlayer Phonons and Moiré Phonons in Twisted Thin‐Layer MoTe2

“…However, research on twisted bilayer MoTe 2 has been scarce [19,20] until very recently, because of challenges associated with producing high-quality samples. Although the occurrence of the quantum anomalous Hall effect [20] and the Mott insulating state [21] has been demonstrated in twisted bilayer MoTe 2 using methods such as magnetic circular dichroism and transport measurements, the characterization of interlayer phonons and Moiré phonons in twisted bilayer MoTe 2 remains unexplored experimentally. Raman spectroscopy, a fast and non-contact optical technique, offers a simple method for characterizing phonon modes in 2D crystals.…”

Directionally-Resolved Phononic Properties of Monolayer 2D Molybdenum Ditelluride (MoTe2) under Uniaxial Elastic Strain

“…In particular, molybdenum ditelluride (MoTe 2 ) is of great interest for its ambient-stable yet readily and reversibly tunable polymorphs, each with drastically different multiphysical and highly layer-dependent intrinsic properties. Evidence of exotic phenomena such as Rydberg excitons, edge supercurrents, , switchable ferromagnetic domains, and fractional quantum anomalous Hall states have also been discovered in various phases of MoTe 2 . The most stable polymorph of MoTe 2 is the semiconducting 2H phase, with an indirect band gap of ∼0.9 eV in its few-layered (2H-) form and a direct band gap of ∼1.1 eV in its monolayer (1H-) form. − This 2H-phase exhibits a trigonal-prismatic crystal structure with the space group P 6 3 / mmc and point group D 3 h . , Additionally, the other polymorphs of MoTe 2 include 1T, 1T′, T d , and 3R phases. , These diverse MoTe 2 polymorphs, each with unique crystal structures, symmetries, and intrinsic properties, allow a myriad of potential applications spanning optoelectronics, superconductors, chemical sensors, neuromorphic elements, and quantum devices. ,− …”

“…In particular, molybdenum ditelluride (MoTe 2 ) is of great interest for its ambient-stable yet readily and reversibly tunable polymorphs, each with drastically different multiphysical and highly layer-dependent intrinsic properties. Evidence of exotic phenomena such as Rydberg excitons, 1 edge supercurrents, 2,3 switchable ferromagnetic domains, 4 and fractional quantum anomalous Hall states 5 have also been discovered in various phases of MoTe 2 . The most stable polymorph of MoTe 2 is the semiconducting 2H phase, with an indirect band gap of ∼0.9 eV in its few-layered (2H-) form and a direct band gap of ∼1.1 eV in its monolayer (1H-) form.…”