Magnetoresistance(MR) provides rich information about Fermi surface, carrier scatterings, and exotic phases for a given electronic system. Here, we report a study of the magnetoresistance for the metallic states in tw...Magnetoresistance(MR) provides rich information about Fermi surface, carrier scatterings, and exotic phases for a given electronic system. Here, we report a study of the magnetoresistance for the metallic states in twisted double bilayer graphene(TDBG). We observe quadratic magnetoresistance in both Moiré valence band(VB) and Moiré conduction band(CB). The scaling analysis shows validity of Kohler's rule in the Moiré valence band. On the other hand, the quadratic magnetoresistance appears near the halo structure in the Moiré conduction band, and it violates Kohler's rule, demonstrating the MR scaling related to band structure in TDBG. We also propose an alternative scaling near the halo structure. Further analysis implies that the observed quadratic magnetoresistance and alternative scaling in conduction band are related to the halo boundary. Our results may inspire investigation on MR in twisted 2D materials and provide new knowledge for MR study in condensed matter physics.展开更多
We theoretically study the band structures and the valley Chern numbers of the AB-AB and AB-BA stacked twisted double bilayer graphene under heterostrain effect.In the absence of heterostrain,due to the constrains by ...We theoretically study the band structures and the valley Chern numbers of the AB-AB and AB-BA stacked twisted double bilayer graphene under heterostrain effect.In the absence of heterostrain,due to the constrains by the spatial symmetries,the central two flat bands of the AB-AB are topological trivial bands,while in the AB-BA they have a finite Chern number.The heterostrain breaks all the point group symmetries and the constrains are lifted,hence the topological properties of the two arrangements can be tuned by different strain magnitudesεand directionsφ.The heterostrain has dissimilar impacts on the Chern numbers of the AB-AB and AB-BA,owing to their different band gaps,and these gaps can be modified by a vertical electric field.Our results show that the topological transitions for both arrangements occur in theεrange of 0.1%-0.4%,which can be realized in the graphene-based sample.展开更多
This paper gives a complete classification of (Δ)-finite twisted double incidence algebras of posets in the case where the Hasse quivers of posets are of type An.
基金supported by the National Key Research and Development Program of China (Grant No. 2020YFA0309600)the National Natural Science Foundation of China (Grant Nos. 61888102, 11834017, and 12074413)+3 种基金the Strategic Priority Research Program of CAS (Grant Nos. XDB30000000 and XDB33000000)the Key-Area Research and Development Program of Guangdong Province (Grant No. 2020B0101340001)supported by the Elemental Strategy Initiative conducted by the MEXT, Japan, Grant Number JPMXP0112101001, JSPS KAKENHI (Grant No. JP20H00354)A3 Foresight by JSPS。
文摘Magnetoresistance(MR) provides rich information about Fermi surface, carrier scatterings, and exotic phases for a given electronic system. Here, we report a study of the magnetoresistance for the metallic states in twisted double bilayer graphene(TDBG). We observe quadratic magnetoresistance in both Moiré valence band(VB) and Moiré conduction band(CB). The scaling analysis shows validity of Kohler's rule in the Moiré valence band. On the other hand, the quadratic magnetoresistance appears near the halo structure in the Moiré conduction band, and it violates Kohler's rule, demonstrating the MR scaling related to band structure in TDBG. We also propose an alternative scaling near the halo structure. Further analysis implies that the observed quadratic magnetoresistance and alternative scaling in conduction band are related to the halo boundary. Our results may inspire investigation on MR in twisted 2D materials and provide new knowledge for MR study in condensed matter physics.
基金the National Natural Science Foundation of China for the support(Grant No.11874271).
文摘We theoretically study the band structures and the valley Chern numbers of the AB-AB and AB-BA stacked twisted double bilayer graphene under heterostrain effect.In the absence of heterostrain,due to the constrains by the spatial symmetries,the central two flat bands of the AB-AB are topological trivial bands,while in the AB-BA they have a finite Chern number.The heterostrain breaks all the point group symmetries and the constrains are lifted,hence the topological properties of the two arrangements can be tuned by different strain magnitudesεand directionsφ.The heterostrain has dissimilar impacts on the Chern numbers of the AB-AB and AB-BA,owing to their different band gaps,and these gaps can be modified by a vertical electric field.Our results show that the topological transitions for both arrangements occur in theεrange of 0.1%-0.4%,which can be realized in the graphene-based sample.
文摘This paper gives a complete classification of (Δ)-finite twisted double incidence algebras of posets in the case where the Hasse quivers of posets are of type An.
