Zhiyu Dong

Sep 13, 2024 | link.aps.org | Zhiyu Dong |Leonid S. Levitov

Stoner magnetism in bands endowed with Berry curvature is shown to be influenced by the coupling between spin-chirality density s·(∂xs×∂ys) and Berry's orbital magnetization. The key effect is that carriers moving in the presence of a spin texture see it as a source of a geometric magnetic field coupled to the carrier's orbital motion through a spin-dependent Aharonov-Bohm effect. This interaction was recently predicted to enable chiral magnons propagating along system boundaries.

Oct 13, 2023 | link.aps.org | Zhiyu Dong |Leonid S. Levitov |Andrey Chubukov

Spin excitations that soften near the onset of magnetic order have long been known to act as “paramagnon” pairing glue that can drive superconductivity. Recent findings of superconductivity in graphene bilayers and trilayers, occurring in the proximity of different itinerant ordered phases polarized in isospin (spin and valley), have motivated us to conduct a comprehensive study of an isospin extension of the paramagnon pairing mechanism in the vicinity of different isospin orders.

May 16, 2023 | link.aps.org | Zhiyu Dong |Olumakinde Ogunnaike |Leonid S. Levitov

Abstract We argue that spin- and valley-polarized metallic phases recently observed in graphene bilayers and trilayers support chiral edge modes that allow spin waves to propagate ballistically along system boundaries without backscattering. The chiral edge behavior originates from the interplay between the momentum-space Berry curvature in Dirac bands and the geometric phase of a spin texture in position space.

May 11, 2023 | link.aps.org | Zhiyu Dong |Andrey Chubukov |Leonid S. Levitov

Abstract We consider the origin of superconductivity found recently in Bernal bilayer graphene at the onset of isospin-polarized order, trying to infer the pairing mechanism and superconducting order from the measurements available to date. The superconductivity is induced by a parallel magnetic field and persists well above the Pauli limit, indicating an unconventional scenario of quantum-critical pairing, where soft fluctuations of isospin give rise to spin-triplet superconductivity.