Charge transfer excitations, pair density waves, and superconductivity in moire materials

Article

关键词: HIGH-TC SUPERCONDUCTIVITY;    CORRELATED STATES;    MODEL;    INSULATOR;    MOTT;   

DOI  :  10.1103/PhysRevB.102.235423

来源: SCIE

【 摘 要 】

Transition-metal dichalcogenide (TMD) bilayers are a new class of tunable moire systems attracting interest as quantum simulators of strongly interacting electrons in two dimensions. In particular, recent theory predicts that the correlated insulator observed in WSe2/WS2 at half filling is a charge-transfer insulator similar to cuprates and, upon further hole doping, exhibits a transfer of charge from anionlike to cationlike orbitals at different locations in the moire unit cell. In this work, we demonstrate that in this doped charge-transfer insulator, tightly bound charge-2e excitations can form to lower the total electrostatic repulsion. This composite excitation, which we dub a trimer, consists of a pair of holes bound to a charge-transfer exciton. When the bandwidth of doped holes is small, trimers crystallize into insulating pair density waves at a sequence of commensurate doping levels. When the bandwidth becomes comparable to the pair binding energy, itinerant holes and charge-2e trimers interact resonantly, leading to unconventional superconductivity similar to superfluidity in an ultracold Fermi gas near Feshbach resonance. Our theory is broadly applicable to strongly interacting charge-transfer insulators, such as WSe2/WS2 or TMD homobilayers under an applied electric field.

【 授权许可】

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