Tunable magnetoresistance in thin-film graphite field-effect transistor by gate voltage
Tunable magnetoresistance in thin-film graphite field-effect transistor by gate voltage
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DOI：
10.1103/physrevb.98.155136
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发表时间：
2018-10
影响因子：
3.7
通讯作者：
T. Taen;K. Uchida;T. Osada;W. Kang
中科院分区：
文献类型：
--
作者：
T. Taen;K. Uchida;T. Osada;W. Kang
磁场诱导石墨的半金属-绝缘体相变引起了人们的关注，尽管其机理还不完全清楚。最近，在脉冲磁场下进行的研究发现，即使在100 nm量级的相对厚的系统中，该相变也依赖于厚度，并且表明绝缘相中的电子状态具有沿着堆叠方向的顺序。在这里，我们报告的直流磁场下观察到的厚度依赖性，这很好地再现了以前的结果下得到的脉冲磁场。为了研究控制相变的临界条件，还研究了场效应晶体管结构中的静电门控效应，因为它会沿堆叠方向沿着引入空间调制。磁阻，测得高达35 T，显着增强的栅极电压，尽管事实上，由于电荷屏蔽效应的基本电子状态没有很大的变化。另一方面，半金属-绝缘体转变的临界磁场被发现是不敏感的栅极电压，而其厚度依赖性是相当确认。通过施加正栅极电压，磁场中的周期性的突出振荡图案变得明显，其起源在此阶段尚不清楚。虽然在这项研究中没有实现相变的静电控制，但门电压可调性的发现将有助于确定石墨中量子极限的电子状态。
Magnetic-field-induced semimetal-insulator phase transition in graphite has regained attention, although its mechanism is not fully understood. Recently, a study performed under the pulsed magnetic field discovered that this phase transition depends on thickness even in a relatively thick system of the order of 100 nm and suggested that the electronic state in the insulating phase has an order along the stacking direction. Here we report the thickness dependence observed under dc magnetic fields, which nicely reproduces the previous results obtained under the pulsed magnetic field. In order to look into the critical condition to control the phase transition, the effect of electrostatic gating is also studied in a field-effect transistor structure since it will introduce a spatial modulation along the stacking direction. Magnetoresistance, measured up to 35 T, is prominently enhanced by the gate voltage in spite of the fact that the underlying electronic state is not largely changed owing to the charge-screening effect. On the other hand, the critical magnetic field of the semimetal-insulator transition is found to be insensitive to gate voltages, whereas its thickness dependence is fairly confirmed. By applying positive gate voltages, a prominent oscillation pattern, periodic in magnetic field, becomes apparent, the origin of which is not clear at this stage. Although electrostatic control of the phase transition is not realized in this study, the findings of gate-voltage tunability will help determine the electronic state in the quantum limit in graphite.