Unusual magnetotransport in twisted bilayer graphene from strain-induced open Fermi surfaces.
Unusual magnetotransport in twisted bilayer graphene from strain-induced open Fermi surfaces.
复制标题
DOI：
10.1073/pnas.2307151120
复制
发表时间：
2023-08-22
影响因子：
11.1
通讯作者：
Goldhaber-Gordon, David
中科院分区：
文献类型：
--
作者：
Wang, Xiaoyu;Finney, Joe;Sharpe, Aaron L.;Rodenbach, Linsey K.;Hsueh, Connie L.;Watanabe, Kenji;Taniguchi, Takashi;Kastner, M. A.;Vafek, Oskar;Goldhaber-Gordon, David
近魔角扭曲双层石墨烯（TBG）由于其丰富的关联相阵列而吸引了凝聚态物理界的注意力。大的莫尔条纹长度尺度不仅促进了相互作用相关的效应，而且还允许诸如应变之类的外在因素发挥主要作用。在以前的工作中，我们提出了测量TBG设备的几个不寻常的行为在磁输运和apertured，单轴应变可以解释我们的测量。在这里，我们的模型磁输运TBG通过将单轴异应变的Bistritzer-麦克唐纳哈密顿。该理论不仅再现了以前工作中的不寻常现象，而且还预测了以前未注意到的其他特征。因此，我们的工作证明了异质应变在TBG器件中的关键作用。玩具Hofstadter模型中的各向异性跳跃最近被用来解释在远离魔角的扭曲双层石墨烯中测量到的丰富而令人惊讶的朗道光谱。怀疑这种各向异性可能会产生意外的单轴应变，我们扩展了Bistritzer-麦克唐纳模型，包括单轴异质应变，并提出了详细的分析其对能带结构和磁输运的影响。我们发现，这种应变强烈影响能带结构，移动三个否则简并货车霍韦点到不同的能量。再加上玻尔兹曼磁输运计算，这再现了以前无法解释的非饱和磁阻在宽范围的密度附近填充和预测微妙的功能，没有注意到在实验数据。与纵向电阻率的这些独特特征相反，霍尔系数几乎不受应变的影响，以至于它在电荷中性点的每一侧仍然显示出单个符号变化-令人惊讶的是，这种符号变化不再发生在货车霍韦点。该理论还预测了一个显着的旋转的电传输主轴填充的功能，即使是固定的应变和刚性带。因此，可以更仔细地检查扭曲双层石墨烯中相互作用诱导的有序度与应变效应。
Because of its rich array of correlated phases, twisted bilayer graphene (TBG) near the magic angle has captivated the condensed matter physics world. The large moiré length scale not only promotes interaction-related effects but also allows for extrinsic factors such as strain to play a major role. In a previous work, we presented measurements of a TBG device with several unusual behaviors in magnetotransport and conjectured that uniaxial strain could explain our measurements. Here, we model magnetotransport in TBG by incorporating uniaxial heterostrain into the Bistritzer–MacDonald Hamiltonian. The theory not only reproduces the unusual phenomena from the previous work but also predicts additional features unnoticed before. Our work therefore demonstrates the crucial role of heterostrain in TBG devices. Anisotropic hopping in a toy Hofstadter model was recently invoked to explain a rich and surprising Landau spectrum measured in twisted bilayer graphene away from the magic angle. Suspecting that such anisotropy could arise from unintended uniaxial strain, we extend the Bistritzer–MacDonald model to include uniaxial heterostrain and present a detailed analysis of its impact on band structure and magnetotransport. We find that such strain strongly influences band structure, shifting the three otherwise-degenerate van Hove points to different energies. Coupled to a Boltzmann magnetotransport calculation, this reproduces previously unexplained nonsaturating magnetoresistance over broad ranges of density near filling and predicts subtler features that had not been noticed in the experimental data. In contrast to these distinctive signatures in longitudinal resistivity, the Hall coefficient is barely influenced by strain, to the extent that it still shows a single sign change on each side of the charge neutrality point—surprisingly, this sign change no longer occurs at a van Hove point. The theory also predicts a marked rotation of the electrical transport principal axes as a function of filling even for fixed strain and for rigid bands. More careful examination of interaction-induced nematic order versus strain effects in twisted bilayer graphene could thus be in order.
登录
查看更多内容
影响因子：
8.6
作者：
Efetov, Dmitri K.;Kim, Philip
通讯作者：
Kim, Philip
影响因子：
3.7
作者：
Goerbig, M. O.;Fuchs, J. -N.;Piechon, F.
通讯作者：
Piechon, F.
影响因子：
3.7
作者：
Cea, Tommaso;Guinea, Francisco
通讯作者：
Guinea, Francisco
DOI：
10.1073/pnas.2118482119
发表时间：
2022-04-19
影响因子：
11.1
作者：
Finney, Joe;Sharpe, Aaron L.;Fox, Eli J.;Hsueh, Connie L.;Parker, Daniel E.;Yankowitz, Matthew;Chen, Shaowen;Watanabe, Kenji;Taniguchi, Takashi;Dean, Cory R.;Vishwanath, Ashvin;Kastner, M. A.;Goldhaber-Gordon, David
通讯作者：
Goldhaber-Gordon, David
影响因子：
8.6
作者：
Cao, Y.;Luo, J. Y.;Jarillo-Herrero, P.
通讯作者：
Jarillo-Herrero, P.