Raman spectroscopy and low temperature magnetotransport studies on hybrid graphene devices

我们打算继续研究混合石墨烯器件的振动和低温磁输运特性，以提高我们对对称性破缺态、分数量子霍尔行为和玻色爱因斯坦凝聚等相关现象的理解和扫描。我们将依靠跨导方法，我们已经确定它在揭示间隙或不可压缩基态方面非常强大。我们将使用电解质门控将我们的输运研究扩展到高密度状态，以研究带结构中的van Hove奇点的后果，并验证最近的理论建议，即在足够高的静电掺杂下可能会在石墨烯中诱导超导性。这些研究将在石墨烯单层和双层上进行。它们将使用在第一个资助期间开发的精密转移技术放置在BN之上，以获得支持设备的最高质量。对于双层结构，将引入一个扭转角作为额外的自由度。扭转导致了一个依赖于角度的低能范霍夫奇点，因此代表了改变整个电子带结构的重要旋钮。在基于电解质门控的器件中，我们还将通过循环伏安法关注在高偏置电压下可能发生的电化学反应。尽管电化学通常被认为是不可取的，但我们认为这些测量本身很有趣，因为它们揭示了离子通过石墨烯片的渗透信息。在多层石墨烯的情况下，这可以被认为是电压驱动的嵌入。我们主要关注的是含锂电解质。

We intend to continue our investigations of the vibrational and low temperature magneto-transport properties of hybrid graphene devices in order to improve our understanding and scan for correlation phenomena such as broken symmetry states, fractional quantum Hall behaviour and Bose Einstein condensation. We will rely on the transconductance method, which we have identified as very powerful in disclosing gapped or incompressible ground states. We will extend our transport studies to the high density regime using electrolyte gating in order to investigate the consequences of the van Hove singularity in the band structure and verify recent theoretical suggestions that it may be possible to induce superconductivity in graphene at sufficiently high electrostatic doping. These studies will be performed on graphene mono- and bilayers. They will be placed on top of BN using the precision transfer technique developed during the first funding period in order to obtain the highest possible quality for supported devices. For bilayers a twist angle will be introduced as an additional degree of freedom. The twist causes an angle dependent low energy van Hove singularity and therefore represents an important knob to modify the overall electronic bandstructure.In devices based on electrolyte gating, we will also pay attention to electrochemical reactions that may occur at high bias voltages by performing cyclic voltammetry. Even though usually the electrochemistry is considered as undesirable, we consider such measurements interesting all by themselves as they reveal information about the permeation of ions through the graphene sheet. In the case of multilayer graphene, this may be considered as voltage driven intercalation. Our main focus will be on Lithium containing electrolytes.