IrTe$_2$ with large spin-orbital coupling (SOC) shows a CDW-like first order structural phase transition from high-temperature trigonal phase to low-temperature monoclinic phase at 270 K, accompanying with a large jump in transport and magnetic measurement as well as in heat capacity. Here, the 3d element Ni has been doped into IrTe$_2$ by growing Ir$_{1-x}$Ni$_x$Te$_2$ single crystals. Both XRD and XPS results reveal that the Ni atoms have substituted for Ir, which is consistent with the calculation result. Like the CDW behaviour, the structural phase transition shows competition and coexistence with the superconductivity. The monoclinic phase transition has been suppressed gradually with the increase of the doping amount of Ni, at last giving rise to the stabilization of the trigonal phase with superconductivity. Within 0.1$\leq$x$\leq$0.2, Ir$_{1-x}$Ni$_x$Te$_2$ shows the superconductive behaviour with T$_c$ around 2.6K. The superconductivity shows anisotropy with dimensionless anisotropy parameter $γ$=$ξ_{//}$$/$$ξ_{\perp}$$\sim$ 2. Even Ni element shows ferromagnetic behaviour, Ir$_{1-x}$Ni$_x$Te$_2$ only shows weak paramagnetism, no ferromagnetic order is observed in it, which is coincident with the calculation result that their up and down spin density of states compensate each other well. In addition, for other 3d elements Fe, Co and Mn doped IrTe$_2$, only Ir$_{1-x}$Mn$_x$Te$_2$ owns magnetism with magnetic moment of 3.0$μ$$_B$ to the supercell, theoretically.
Coexistence of Rashba and Ising Spin-Singlet Pairings in Two-Dimensional IrTe$_{2}$
Indian Association for the Cultivation of Science（印度科学文化研究所）；Indian Institute of Science（印度科学学院）；Dr. B. R. Ambedkar Institute of Technology（B.R. 安贝德卡尔理工学院）；S. N. Bose National Centre for Basic Sciences（S.N. 玻色基础科学国家中心）；Masaryk University（马萨里克大学）
Superconductivity in the vicinity of a competing electronic order often manifests itself with a superconducting dome, centred at a presumed quantum critical point in the phase diagram. This common feature, found in many unconventional superconductors, has supported a prevalent scenario that fluctuations or partial melting of a parent order are essential for inducing or enhancing superconductivity. Here we present a contrary example, found in IrTe2 nanoflakes of which the superconducting dome is identified well inside the parent stripe charge ordering phase in the thickness-dependent phase diag…
The interplay among various collective electronic states such as superconductivity (SC) and charge density wave (CDW) is of tremendous significance in low-dimensional transition metal dichalcogenides. Thus far, a consensus on the relationship between SC and CDW has not been established in IrTe2, where either competing or collaboration pictures have been suggested in the bulk or thick flakes. Here, we use the state-of-art Au-assisted exfoliation method to overcome the obstacle of interlayer Te-Te bonding, cleaving the IrTe2 down to monolayer for the first time. A striking feature revealed by an…
Structural phase transition in IrTe$_2$: A combined study of optical spectroscopy and band structure calculations
Ir $_{1-x}$ Pt $_x$ Te $_2$是一个有趣的体系，表现出结构不稳定性和超导电性之间的竞争现象。由于Ir和Te的大原子序数，自旋-轨道耦合在该系统中预计是强的，这可能导致非常规的超导性。我们生长了该系统的单晶样品，并研究了它们的电子性质。特别是，我们进行了光学光谱测量，结合密度函数计算，在努力阐明的起源在280 K的结构相变的未掺杂的化合物IrTe $_2$。测量结果表明，在相变以下的能带结构和导电载流子的显着减少的戏剧性重建。我们阐述了这种跃迁不是由密度波型不稳定性驱动的，而是由晶体场效应引起的，晶体场效应进一步分裂/分离了Te（p $_x$，p $_y$）和Te p $_z$带的能级.
This work presents the emergence of superconductivity in Ir - doped Weyl semimetal T$_d$ - MoTe$_{2}$ with broken inversion symmetry. Chiral anomaly induced planar Hall effect and anisotropic magneto-resistance confirm the topological semimetallic nature of Mo$_{1-x}$Ir$_{x}$Te$_{2}$. Observation of weak anisotropic, moderately coupled type-II superconductivity in T$_d$ -Mo$_{1-x}$Ir$_{x}$Te$_{2}$ makes it a promising candidate for topological superconductor.
Computational Materials Design for High Critical Temperature Superconductivity in Hole-Doped Delafossite CuAlO$_2$: Transparent Superconductors
基于第一性原理计算了空穴掺杂铜铁矿CuAlO $_2$的超导临界温度$T_c$。根据我们的计算，$0.2\sim0.3$空穴掺杂CuAlO $_2$可以成为声子介导的高$T_c$超导体，其$T_c\sim50$ K。在空穴掺杂的CuAlO $_2$中，拉伸O-Cu-O哑铃的A $_1$ L $_1$声子模与Cu 3d $_{3z^2-r^2}$的平带和O 2 p $_z$的反键$π$ -带的电子有很强的电子-声子相互作用.
Superconductivity in the new polymerized C60 fullerite clathrate doped with simple metals was investigated through density functional theory methods. The phonon dispersion curves were systematically computed for the clathrate structures containing the guest dopants (Li, Na, K, Be, Mg, Ca, Al, Ga, Ge) in one of the two distinct cages, fullerene-like C60 and sodalite-like C24, exhibited by this structure. Only four of these structures, Li@C24, Na@C24, Ga@C24 and Be@C60, are dynamically stable in the harmonic approximation. They all show superconducting behavior, although their critical temperatu…
Nuclear magnetic relaxation rates of unconventional superconductivity in doped topological insulators
我们研究了掺杂拓扑绝缘体$M$（$=$ Cu，Nb，Sr）$_{x}$ Bi $_{2}$ Se $_{3}$和Sn $_{1-x}$ In $_{x}$ Te中的核磁弛豫速率与温度的关系，以检测拓扑超导性的迹象。临界温度Tc以下的Hebel-Slichter相干效应依赖于掺杂拓扑绝缘体的最小模型所预测的超导态。在类似于$^{3}$ He中的ABM相的节点各向异性拓扑状态中，NMR速率在Tc以下具有常规的$s$波状相干峰。相比之下，在完全带隙的各向同性拓扑超导状态下，低于Tc的速率呈现出反峰轮廓。此外，在二重面内各向异性拓扑超导态中，不存在与手征$p$波态类似的相干效应。因此，我们揭示了NMR速率揭示了掺杂拓扑绝缘体的非常规超导性。
Adsorption of one-third monolayer of Sn on an atomically-clean Si(111) substrate produces a two-dimensional triangular adatom lattice with one unpaired electron per site. This dilute adatom reconstruction is an antiferromagnetic Mott insulator; however, the system can be modulation-doped and metallized using heavily-doped p-type Si(111) substrates. Here, we show that the hole-doped dilute adatom layer on a degenerately doped p-type Si(111) wafer is superconducting with a critical temperature of 4.7 +- 0.3 K. While a phonon-mediated coupling scenario would be consistent with the observed TC, Mo…
T-carbon has been proposed as a new carbon allotrope in 2011, which was successfully synthesized in recent experiments. Because of its fluffy structure, several kinds of atoms can be intercalated into T-carbon, making it a versatile candidate in various applications such as hydrogen storage, perovskite solar cells, lithium ion batteries, thermoelectrics, photocatalyst, etc. Here we show that superconductivity can appear in Na-doped T-carbon with superconducting transition temperature Tc of 11 K at ambient pressure, and Tc can be enhanced to 19 K under pressure of 14 GPa, which results from an …
Insight into why superconductivity in pristine and doped monolayer graphene seems strongly suppressed has been central for the recent years' various creative approaches to realize superconductivity in graphene and graphene-like systems. We provide further insight by studying electron-phonon coupling and superconductivity in doped monolayer graphene and hexagonal boron nitride based on intrinsic phonon modes. Solving the graphene gap equation using a detailed model for the effective attraction based on electron tight binding and phonon force constant models, the various system parameters can be…
Recent experiments on Nb-doped SrTiO$_3$ have shown that the superconducting energy gap to the transition temperature ratio maintains the Bardeen-Cooper-Schrieffer (BCS) value throughout its superconducting dome. Motivated by these and related studies, we show that the Cooper pairing mediated by a single soft transverse-optical phonon is the most natural mechanism for such a superconducting dome given experimental constraints, and present the microscopic theory for this pairing mechanism. Furthermore, we show that this mechanism is consistent with the $T^2$ resistivity in the normal state. Las…
Signature of proximity induced triplet superconductivity in junctions made of the doped topological insulator $\rm Bi_2Se_3$ and the s-wave superconductor NbN
Two-gap superconductivity in heavily n-doped graphene: ab initio Migdal-Eliashberg theory
石墨烯是从零维到三维材料的碳家族中唯一尚未观察到超导性的成员。目前尚不清楚对超导石墨烯的探索是否受到技术挑战的阻碍，或者是二维序参量的波动。在这一领域，从头计算是有用的，以指导实验工作，缩小搜索空间。本着这种精神，我们从第一原理研究了使用由Wannier-Fourier插值提供动力的完全各向异性Migdal-Eliashberg理论在掺杂石墨烯中诱导超导性的可能性。为了解决最好的情况下，我们考虑在高载流子密度的电子和空穴掺杂，以便对准费米能级的范霍夫奇点。在这些条件下，我们发现超导间隙的$s$波对称性，与轻微的各向异性引起的三角形翘曲，并在$n$掺杂的石墨烯的情况下，一个意想不到的两个间隙结构联想到MgB $_2$。我们的Migdal-Eliashberg计算表明，对于载流子密度超过$10^{15}$ cm $^{-2}$的$n$掺杂的石墨烯，在低温下观察到超导性应该是可能的。
