Emergence of charge density wave domain walls above the superconducting dome in 1T-TiSe2
Emergence of charge density wave domain walls above the superconducting dome in 1T-TiSe2
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DOI：
10.1038/nphys2935
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发表时间：
2014-06-01
期刊：
影响因子：
19.6
通讯作者：
Abbamonte, P.
中科院分区：
文献类型：
--
作者：
Joe, Y. I.;Chen, X. M.;Abbamonte, P.
在所谓的非常规超导体中，超导电性几乎总是存在于另一个有序状态的附近，例如反铁磁性、电荷密度波(CDW)或条带有序。这表明超导电性与其他序参数的涨落之间存在着根本的联系。为了更好地理解这种联系，我们利用高压X射线散射直接研究了层状二卤化物TiSe2中的CDW有序，以前的研究表明，当CDW被压力(1)或铜原子嵌入(2)抑制时，TiSe2表现出超导电性。我们成功地将CDW完全抑制到零温度，首次确定了在P-c=5.1+/-0.2 Gpa处存在水量子临界点(QCP)，该临界点位于超导区末端以外的1 Gpa以上。出乎意料的是，在P=3 GPA时，我们观察到了一个重入的弱一级无公度相，这表明在超导穹顶上方的某个地方存在一个Lifshitz三临界点。我们的研究表明，TiSe_2的超导电性可能不是与QCP本身有关，而是与CDW畴壁的形成有关。
Superconductivity in so-called unconventional superconductors is nearly always found in the vicinity of another ordered state, such as antiferromagnetism, charge density wave (CDW), or stripe order. This suggests a fundamental connection between superconductivity and fluctuations in some other order parameter. To better understand this connection, we used high-pressure X-ray scattering to directly study the CDW order in the layered dichalcogenide TiSe2, which was previously shown to exhibit superconductivity when the CDW is suppressed by pressure(1) or intercalation of Cu atoms(2). We succeeded in suppressing the CDW fully to zero temperature, establishing for the first time the existence of aquantum critical point (QCP) at P-c = 5.1 +/- 0.2 GPa, which is more than 1 GPa beyond the end of the superconducting region. Unexpectedly, at P = 3 GPa we observed a reentrant, weakly first order, incommensurate phase, indicating the presence of a Lifshitz tricritical point somewhere above the superconducting dome. Our study suggests that superconductivity in TiSe2 may not be connected to the QCP itself, but to the formation of CDW domain walls.