Controlling many-body states by the electric-field effect in a two-dimensional material
Controlling many-body states by the electric-field effect in a two-dimensional material
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DOI：
10.1038/nature18453
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发表时间：
2016-06
期刊：
影响因子：
64.8
通讯作者：
L. Li;E. O’Farrell;K. Loh;G. Eda;B. Özyilmaz;A. C. Neto
中科院分区：
文献类型：
--
作者：
L. Li;E. O’Farrell;K. Loh;G. Eda;B. Özyilmaz;A. C. Neto
为了理解具有强电子-电子相互作用的系统的复杂物理学，理想的方法是控制和监测其属性，同时调整施加到系统的外部电场（电场效应）。事实上，在强关联电子系统中对多体状态的完全电场控制是下一代凝聚态研究和设备的基础。然而，材料必须足够薄以避免屏蔽块状材料中的电场。二维材料不经历电屏蔽，并且它们的电荷载流子密度可以通过选通来控制。八面体二硒化钛（1 T-TiSe 2）是一种典型的二维材料，在其相图中显示出电荷密度波（CDW）和超导性，与其他层状系统（如氧化铜，铁磷属元素，稀土元素和锕系元素原子的晶体）有几处相似之处。通过研究厚度为10纳米或更小的1 T-TiSe 2单晶，封装在二维层的六方氮化硼中，我们实现了对CDW转变温度（从170开尔文调整到40开尔文）和超导转变温度（从0开尔文的量子临界点调整到3开尔文）的前所未有的控制。电驱动TiSe 2在不同的有序电子相，使我们能够研究的细节之间的相变多体状态。由Little-Parks效应引起的磁阻周期振荡的观测表明，超导性的出现与超导性序参量的振幅和相位的空间织构直接相关，对应于超导性的二维矩阵。我们推断，这种超导矩阵是由嵌入在公度CDW状态的非公度CDW状态的矩阵支持。我们的结果表明，空间调制的电子态是基本的二维超导电性的外观。
To understand the complex physics of a system with strong electron–electron interactions, the ideal is to control and monitor its properties while tuning an external electric field applied to the system (the electric-field effect). Indeed, complete electric-field control of many-body states in strongly correlated electron systems is fundamental to the next generation of condensed matter research and devices,,. However, the material must be thin enough to avoid shielding of the electric field in the bulk material. Two-dimensional materials do not experience electrical screening, and their charge-carrier density can be controlled by gating. Octahedral titanium diselenide (1T-TiSe2) is a prototypical two-dimensional material that reveals a charge-density wave (CDW) and superconductivity in its phase diagram, presenting several similarities with other layered systems such as copper oxides, iron pnictides, and crystals of rare-earth elements and actinide atoms. By studying 1T-TiSe2single crystals with thicknesses of 10 nanometres or less, encapsulated in two-dimensional layers of hexagonal boron nitride, we achieve unprecedented control over the CDW transition temperature (tuned from 170 kelvin to 40 kelvin), and over the superconductivity transition temperature (tuned from a quantum critical point at 0 kelvin up to 3 kelvin). Electrically driving TiSe2over different ordered electronic phases allows us to study the details of the phase transitions between many-body states. Observations of periodic oscillations of magnetoresistance induced by the Little–Parks effect show that the appearance of superconductivity is directly correlated with the spatial texturing of the amplitude and phase of the superconductivity order parameter, corresponding to a two-dimensional matrix of superconductivity. We infer that this superconductivity matrix is supported by a matrix of incommensurate CDW states embedded in the commensurate CDW states. Our results show that spatially modulated electronic states are fundamental to the appearance of two-dimensional superconductivity.