AxFe2Se2（A=K，Cs）中重电子掺杂的电子结构和各向同性超导能隙

重过掺杂（Bi，Pb）_2Sr_2CuO_6中Eliashberg函数的定量测定及电子与多声子模强耦合的证据

Quantitative Determination of Eliashberg Function and Evidence of Strong Electron Coupling with Multiple Phonon Modes in Heavily Over doped (Bi,Pb)2Sr2CuO6

用超高分辨激光角分辨光电子能谱测量了重掺杂（Bi，Pb）_2Sr_2CuO_6（Tc> 5K）超导体。利用准粒子色散在不同温度下的细微变化的高精度数据，我们开发了一个通用的程序来确定裸带色散和定量提取玻色子谱函数。我们的研究结果明确表明，70毫电子伏的节点扭结是由于电子耦合的多声子模式，具有很大的质量增强因子λ = 0.42，即使在重度过掺杂制度。

Enhanced superconductivity and moderate spin fluctuations suppressed at low energies in heavily electron-doped La1111-based superconductor

To elucidate the origin of re-enhanced high-$T_c$ phase in the heavily electron-doped Fe-pnictides, systematic $^{75}$As NMR studies are performed on heavily electron-doped LaFe$Pn$O$_{0.75}$H$_{0.25}$ by controlling the pnictogen height ($h_{Pn}$) from the Fe plane through the substitution at $Pn$(=As) site with Sb or P. The measurements of nuclear spin relaxation rate (1/$T_1$) and Knight shift ($K$) reveal that the moderate spin fluctuations at high temperatures are suppressed toward low temperatures. Such characteristic spin fluctuations with gap like feature at low energies are more enlar…

Effect of on-site Coulomb repulsion on ferromagnetic fluctuations in heavily over-doped cuprates

We theoretically study ferromagnetic (FM) fluctuations that are experimentally observed in the heavily overdoped region of cuprate superconductors. To explore the origin of FM fluctuations, we evaluate the spin susceptibilities of a single-band Hubbard model within the fluctuation exchange approximation. Model parameters are derived using the Wannierization technique and the constrained random phase approximation method based on the maximally localized Wannier functions. The constrained random phase approximation calculations reveal that the on-site Coulomb interaction decreases with an increa…

Andreev反射谱中重掺Zn的$YBa_2Cu_3O_{7-δ}$中s波配对的证据

Evidence of a s-Wave Pairing in Heavily Zn-doped $YBa_2Cu_3O_{7-δ}$ from Andreev Reflection Spectra

当在$YBa_2Cu_3O_{7-δ}$中通过Zn掺杂抑制$d_{x^2-y^2}$波配对时，发现一些Andreev反射光谱与常规超导体的s波光谱相似。能隙是相当可重复的（2.3-3.0meV）。它被低磁场（$H_C^{PC}=120-270mT$）抑制，这与d波谱（$H_C^{PC}>3T$）形成了很大的对比，具有相似的能隙值。我们假设s波配对发生在Zn杂质附近。

重掺硼（111）金刚石薄膜的超导电性优势

Advantage on Superconductivity of Heavily Boron-Doped (111) Diamond Films

在高硼掺杂浓度为8.4E21cm-3（4.7atomic%）的同质外延（111）金刚石薄膜上实现了目前金刚石中最高的超导转变温度Tc（onset）为11.4K，Tc（offset）为7.4K。在相同的硼浓度下，（111）金刚石薄膜的Tc值比（100）金刚石薄膜的Tc值高一倍以上。掺硼（111）金刚石的Tc随着硼含量的增加而增加，直到最大掺入浓度，并且与使用McMillan方程估计的值一致。（111）金刚石膜的有利Tc是由于较高的载流子浓度超过其硼浓度。

Superconductivity at 48 K of heavily hydrogen-doped SmFeAsO epitaxial films grown by topotactic chemical reaction using CaH2

High-critical-temperature (Tc) superconductivity at 48 K is reported for hydrogen-doped SmFeAsO epitaxial films on MgO single-crystal substrates. The key processes are pulsed laser deposition to grow undoped SmFeAsO epitaxial films and subsequent topotactic chemical reaction using CaH2 powders under evacuated silica-glass ampule atmosphere. Based on this post-deposition thermal annealing treatment that we have developed, a maximum hydrogen concentration x = ~0.35 was realized in SmFeAs(O1-xHx). Disordered hydrogen-substitution at O sites is experimentally confirmed directly by atomic-scale mic…

Quantum critical behavior in heavily doped LaFeAsO$_{1-x}$H$_x$ pnictide superconductors analyzed using nuclear magnetic resonance

We studied the quantum critical behavior of the second antiferromagnetic (AF) phase in the heavily electron-doped high-$T_c$ pnictide, LaFeAsO$_{1-x}$H$_x$ by using $^{75}$As and $^{1}$H nuclear-magnetic-resonance (NMR) technique. In the second AF phase, we observed a spatially modulated spin-density-wave-like state up to $x$=0.6 from the NMR spectral lineshape and detected a low-energy excitation gap from the nuclear relaxation time $T_1$ of $^{75}$As. The excitation gap closes at the AF quantum critical point (QCP) at $x \approx 0.49$. The superconducting (SC) phase in a lower-doping regime …

Pressure-induced quantum critical point in a heavily hydrogen-doped iron-based superconductor LaFeAsO

An iron-based superconductor LaFeAsO$_{1-x}$H$_x$ (0 $\leq x \leq$ 0.6) undergoes two antiferromagnetic (AF) phases upon H doping. We investigated the second AF phase ($x$=0.6) using NMR techniques under pressure. At pressures up to 2 GPa, the ground state is a spin-density-wave state with a large gap; however, the gap closes at 4.0 GPa, suggesting a pressure-induced quantum critical point. Interestingly, the gapped excitation coexists with gapless magnetic fluctuations at pressures between 2 and 4 GPa. This coexistence is attributable to the lift up of the $d_{xy}$ orbital to the Fermi level,…

High-Tc superconductivity up to 55 K under high pressure in the heavily electron doped Lix(NH3)yFe2Se2 single crystal

We report a high-pressure study on the heavily electron doped Lix(NH3)yFe2Se2 single crystal by using the cubic anvil cell apparatus. The superconducting transition temperature Tc = 44 K at ambient pressure is first suppressed to below 20 K upon increasing pressure to Pc = 2 GPa, above which the pressure dependence of Tc(P) reverses and Tc increases steadily to ca. 55 K at 11 GPa. These results thus evidenced a pressure-induced second high-Tc superconducting (SC-II) phase in Lix(NH3)yFe2Se2 with the highest Tcmax = 55K among the FeSe-based bulk materials. Hall data confirm that in the emergent…

重掺杂石墨烯的双能隙超导性：从头算Migdal-Eliashberg理论

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。

用核磁共振技术探测重掺杂LaFeAsO1-xHx磷属元素化物超导体中的反铁磁有序

Detection of antiferromagnetic ordering in heavily doped LaFeAsO1-xHx pnictide superconductors using nuclear-magnetic-resonance techniques

利用~（75）As-和~ 1H-核磁共振技术研究了LaFeAsO_（1-x）H_x中的双超导（SC）穹，意外地发现在进一步掺H时，在双SC穹之后出现了一个新的反铁磁（AF）相，在电子相图中形成了AF相和SC相的对称排列。我们证明了新的AF排序起源于电子口袋之间的嵌套，不像在大多数未掺杂的pnictides中看到的电子和空穴口袋之间的嵌套。新的AF排序是来自于共同的高Tc磷属元素化物的功能：然而，它还没有被报道，因为它们的电子掺杂能力差的其他高Tc磷属元素化物。

Irradiation induced modification of the superconducting properties of heavily boron doped diamond

Diamond, a wide band-gap semiconductor, can be engineered to exhibit superconductivity when doped heavily with boron. The phenomena has been demonstrated in samples grown by chemical vapour deposition where the boron concentration exceeds the critical concentration for the metal-to-insulator transition of $n_{MIT} \gtrsim 4\times10^{20}/\text{cm}^3$. While the threshold carrier concentration for superconductivity is generally well established in the literature, it is unclear how well correlated higher critical temperatures are with increased boron concentration. Previous studies have generally…

Quantum Phase transition under pressure in a heavily hydrogen-doped iron-based superconductor LaFeAsO

Hydrogen (H)-doped LaFeAsO is a prototypical iron-based superconductor. However, its phase diagram extends beyond the standard framework, where a superconducting (SC) phase follows an antiferromagnetic (AF) phase upon carrier doping; instead, the SC phase is sandwiched between two AF phases appearing in lightly and heavily H-doped regimes. We performed nuclear magnetic resonance (NMR) measurements under pressure, focusing on the second AF phase in the heavily H-doped regime. The second AF phase is strongly suppressed when a pressure of 3.0 GPa is applied, and apparently shifts to a highly H-do…

Zn掺杂和重欠掺杂YBa2Cu3O7-d低温下的异常电荷局域化

Unusual Charge Localization in Zn-doped and Heavily Underdoped YBa2Cu3O7-d at Low Temperatures

在磁场高达18 T的条件下，测量了Zn掺杂YBa_2Cu_3 O_（7-d）和重欠掺杂纯YBCO单晶的面内正常态电阻率。我们发现，正常态rho_ab的温度依赖性不服从log（1/T），在低温极限下不趋于发散。结果表明，YBCO正常态的"基态"是金属态.

Heavily Hydride-ion-doped 1111-type Iron-based Superconductors: Synthesis, Physical Properties and Electronic Structure

Iron-based superconductors have grown to be a new continent of high Tc superconductors comparable to cuprates. The optimal critical temperature (Tc) of 56 K in electron-doped 1111-type iron oxypnictides attracts considerable attention of physicists and chemists. Carrier doping is not only essential to induce superconductivity but also is a critical parameter that governs the electronic, magnetic, and crystallographic properties of ground states in high-Tc superconductors. Hydride ion (H-) which is an anionic state of hydrogen acts as an efficient electron donor in the 1111-type, leading to sev…

Pairing Mechanism of the Heavily Electron Doped FeSe Systems: Dynamical Tuning of the Pairing Cutoff Energy

We studied pairing mechanism of the heavily electron doped FeSe (HEDIS) systems, which commonly have one incipient hole band -- a band top below the Fermi level by a finite energy distance $ε_b$ -- at $Γ$ point and ordinary electron bands at $M$ points in Brillouin zone (BZ). We found that the system allows two degenerate superconducting solutions with the exactly same $T_c$ in clean limit: the incipient $s^{\pm}_{he}$-gap ($Δ_h^{-} \neq 0$, $Δ_e^{+} \neq 0$) and $s_{ee}^{++}$-gap ($Δ_h =0$, $Δ_e^{+} \neq 0$) solutions with different pairing cutoffs, $Λ_{sf}$ (spin fluctuation energy) and $ε_b…

Isotropic Quenched Disorder Triggers a Robust Nematic State in Electron-Doped Pnictides

The phase diagram of electron-doped pnictides is studied varying the temperature, electronic density, and isotropic quenched disorder strength by means of computational techniques applied to a three-orbital ($xz$, $yz$, $xy$) spin-fermion model with lattice degrees of freedom. In experiments, chemical doping introduces disorder but in theoretical studies the relationship between electronic doping and the randomly located dopants, with their associated quenched disorder, is difficult to address. In this publication, the use of computational techniques allows us to study independently the effect…

Extreme anisotropy and anomalous transport properties of heavily electron doped Lix(NH3)yFe2Se2 single crystals

The missing hole packets near the Brillouin zone center render unique electronic structures to the heavily electron doped FeSe-based superconductors with Tc above 40 K. It challenges the existing scenario accounting for the nature of superconductivity in the iron-based family. Yet, one hurdle that has to be overcome is the materials complexity in the rather limited number of compounds. Here we report the growth of heavily electron doped Li-NH3 intercalated FeSe single crystals that are free of such complexities and allow access to the intrinsic superconducting properties. Our results show extr…

Elastoresistivity of heavily hole doped 122 iron pnictides superconductors

Nematicity in the heavily hole-doped iron pnictide superconductors remains controversial. Sizeable nematic fluctuations and even nematic orders far from a magnetic instability were declared in RbFe$_2$As$_2$ and its sister compounds. Here we report a systematic elastoresistance study of series of isovalent- and electron-doped KFe$_2$As$_2$ crystals. We found divergent elastoresistance upon cooling for all the crystals along their [110] direction. The amplitude of elastoresistivity diverges if K is substituted with larger ions or if the system is driven towards a Lifshitz transition. However, w…

重掺硼硅外延层中Bardeen-Cooper-Schrieffer超导电性的亚开尔文隧道谱研究

Subkelvin tunneling spectroscopy showing Bardeen-Cooper-Schrieffer superconductivity in heavily boron-doped silicon epilayers

在亚开尔文温度范围内对掺硼的超导硅外延层进行了扫描隧道谱研究。由此产生的局部微分电导表现为均匀超导体的预期，能隙色散低于+/-10%。超导能隙的光谱形状、振幅和温度依赖性符合BCS模型，进一步支持了弱耦合极限下声子介导的空穴配对机制的假设.

重电子掺杂BaFe $_{1.7}$ Co $_{0.3}$ As $_2$电子结构的角分辨光电子能谱研究

Electronic structure of heavily electron-doped BaFe$_{1.7}$Co$_{0.3}$As$_2$ studied by angle-resolved photoemission

我们对重电子掺杂非超导BaFe $_{1.7}$ Co $_{0.3}$ As $_2$进行了高分辨角分辨光电子能谱研究。我们发现在空穴掺杂的超导体Ba $_{0.6}$ K $_{0.4}$ Fe $_2$ As $_2$中观察到的两个空穴费米面口袋在该化合物中不存在或非常小，而在M点处的两个电子口袋由于Co替代的电子掺杂而显著膨胀。非SC和SC样品的费米面的比较表明，通过反铁磁波矢连接的空穴和电子口袋的共存是实现铁基超导体的超导性机制的必要条件。

Observation of Double-Dome Superconductivity in Potassium-Doped FeSe Thin Films

We report on the emergence of two disconnected superconducting domes in alkali-metal potassium (K)-doped FeSe ultra-thin films grown on graphitized SiC(0001). The superconductivity exhibits hypersensitivity to K dosage in the lower-Tc dome, whereas in the heavily electron-doped higher-Tc dome it becomes spatially homogeneous and robust against disorder, supportive of a conventional Cooper-pairing mechanism. Furthermore, the heavily K-doped multilayer FeSe films all reveal a large superconducting gap of ~ 14 meV, irrespective of film thickness, verifying the higher-Tc superconductivity only in …

Orbital and Pauli limiting effects in heavily doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$

We investigated the thermodynamic properties of the Fe-based lightly disordered superconductor Ba$_{0.05}$K$_{0.95}$Fe$_2$As$_2$ in external magnetic field H applied along the FeAs layers (H//ab planes). The superconducting (SC) transition temperature for this doping level is T$_c$ = 6.6 K. Our analysis of the specific heat C(T,H) measured for T < T$_c$ implies a sign change of the superconducting order parameter across different Fermi pockets. We provide experimental evidence for the three components superconducting order parameter. We find that all three components have values which are comp…

重电子掺杂Li $_{1+x}$ FeAs中高能扭折结构的磁起源

Magnetic origin of high-energy kink structure in heavily electron-doped Li$_{1+x}$FeAs

我们报道了用三维角分辨光电子能谱观察到的重电子掺杂非超导Li $_{1+x}$ FeAs的高能扭结结构的起源。在布里渊区中心的$d_{xy}$轨道强烈重整化，表明更强的电子相关性，超过化学计量比的LiFeAs，尽管事实上，所有频带的轨道特征保持不变。在$d_{yz}$能带上发现了两种类型的扭折结构：在20 meV的结合能处的各向同性扭折和仅在（110）方向上观察到的位于100 meV处的另一种扭折。较高能量的扭结被认为是源于磁相互作用，因为峰值能量与自旋激发的能量一致。

重电子掺杂铁硒超导体中由多Q自旋涨落驱动的电荷序

Charge order driven by multiple-Q spin fluctuations in heavily electron-doped iron selenide superconductors

本文利用扫描隧道显微镜在Fe位缺陷抑制超导的重电子掺杂铁硒化物中发现短程棋盘状电荷序，并通过模拟证明其由多Q自旋密度波驱动，揭示了竞争序的存在及电荷序探测自旋涨落的潜力。

掺钴SrFe2As2外延薄膜中的准各向同性上临界场

Psuedo-isotropic upper critical field in cobalt-doped SrFe2As2 epitaxial films

本文报道了在Tc ~ 0.5 K范围内，在高达50 T的脉冲磁场中，掺钴SrFe_2As_2外延薄膜的上临界场（H_c ~ 2）随温度和角度的变化关系。对于H平行线c，Hc 2接近于温度的线性函数，而在垂直方向上存在显著的向下曲率，这导致Hc 2比率（γ = Hc 2（垂直）/Hc 2（平行））随温度几乎线性地减小，在Hc 2（0）= 47 T的低温下接近γ = 1。我们测量完整的上临界场相图，包括角度依赖性和模型的数据使用两个波段的理论，使我们能够确定两个波段的各向异性，它们的相对扩散系数，和BCS耦合常数矩阵元素之间的关系。我们发现一个不寻常的两个带的扩散系数之间的关系，有两个各向异性和相反的频带。这种关系是由观察到的局部最大值Hc 2（平行）在低温下。

重掺杂MoS2中的相互作用和超导电性

Interactions and superconductivity in heavily doped MoS2

我们分析了最近在MoS $_2$中观察到的超导相的微观起源和物理性质。我们展示了如何的导带的谷结构的组合，密度依赖的屏蔽的远程库仑相互作用，短程电子排斥，和相对薄弱的电子-声子相互作用，使得可能存在的超导序参量具有相反的符号在不同的山谷，类似的超导性中发现的pnictides和铜酸盐的相。

Evolution from $B_{2g}$ nematics to $B_{1g}$ nematics in heavily hole-doped iron-based superconductors

Recent experiments reported an unusual nematic behavior of heavily hole-doped pnictides $A$Fe$_{2}$As$_{2}$, with alkali $A$ = Rb, Cs. In contrast to the $B_{2g}$ nematic order of the parent $Ae$Fe$_{2}$As$_{2}$ compounds (with alkaline earth $Ae$ = Sr, Ba), characterized by unequal nearest-neighbor Fe-Fe bonds, in the hole-doped systems nematic order is observed in the $B_{1g}$ channel, characterized by unequal next-nearest-neighbor Fe-Fe (diagonal Fe-As-Fe) bonds. In this work, using density functional theory, we attribute this behavior to the evolution of the magnetic ground state along the…

Co取代NaFeAs的能带结构从最佳掺杂到重过掺杂的演化

Evolution of band structure from optimally doped to heavily overdoped Co-substituted NaFeAs

用角分辨光电子能谱研究了NaFe $_{1-x}$ Co $_x$ As从最佳掺杂超导化合物（$x=0.028$）到重过掺杂非超导化合物（$x=0.109$）的电子结构。与“122”型铁磷属元素化合物的情况类似，我们的数据表明，在NaFe $_{1-x}$ Co $_x$ As中的Co掺杂提供了额外的载流子，并相应地移动了费米能级。在$x=0.109$化合物中，围绕带中心$Γ$的空穴状带移动到更深的结合能，而出现电子口袋。在整个掺杂范围内，我们研究的整体能带重整化基本上保持不变，这表明局部磁/电子相关性不受载流子掺杂的影响。我们推测，流动载流子的巡游特性和局域相互作用之间的平衡可能对超导性起着重要的作用。

20 K superconductivity in heavily electron doped surface layer of FeSe bulk crystal

A superconducting transition temperature Tc as high as 100 K was recently discovered in 1 monolayer (1ML) FeSe grown on SrTiO3 (STO). The discovery immediately ignited efforts to identify the mechanism for the dramatically enhanced Tc from its bulk value of 7 K. Currently, there are two main views on the origin of the enhanced Tc; in the first view, the enhancement comes from an interfacial effect while in the other it is from excess electrons with strong correlation strength. The issue is controversial and there are evidences that support each view. Finding the origin of the Tc enhancement co…

重掺杂Ba $_{1-x}$ K $_{x}$ Mn $_{2}$ As $_{2}$中新的弱铁磁金属态

Novel weak-ferromagnetic metallic state in heavily doped Ba$_{1-x}$K$_{x}$Mn$_{2}$As$_{2}$

成功地生长了重掺杂Ba $_{1-x}$ K $_{x}$ Mn $_{2}$ As $_{2}$（$x$ =0.19和0.26）单晶，并对其电阻率和各向异性磁化率进行了测量。与未掺杂的BaMn $_{2}$ As $_{2}$的反铁磁绝缘基态相反，K掺杂的晶体在低于$\sim$ 50 K时显示出金属导电性，具有弱铁磁性，而在高于$\sim$ 50 K时显示出Curie-Weiss类面内磁化率。在高达6 GPa的高压下，低温金属性转变为以Kondo型电阻率最小值为特征的状态，而在2.5K以上没有任何超导性特征。使用$2\times2\times1$超晶胞对$x$ =0.25的电子结构计算再现了空穴掺杂金属态。费米能级处的态密度具有明显的As 4 $p$分量，表明4 $p$空穴是金属导电的主要原因.我们的研究结果表明，巡游4 $p$空穴和本地3 $d$矩之间的相互作用是主要负责的新的金属状态。

Structure of spin excitations in heavily electron-doped Li0.8Fe0.2ODFeSe superconductors

Heavily electron-doped iron-selenide (HEDIS) high-transition-temperature (high-$T_{\rm{c}}$) superconductors, which have no hole Fermi pockets, but have a notably high $T_{\rm{c}}$, have challenged the prevailing $s$$_\pm$ pairing scenario originally proposed for iron pnictides containing both electron and hole pockets. The microscopic mechanism underlying the enhanced superconductivity in HEDIS remains unclear. Here, we used neutron scattering to study the spin excitations of the HEDIS material Li$_{0.8}$Fe$_{0.2}$ODFeSe ($T_{\rm{c}}$ = 41 K). Our data revealed nearly ring-shaped magnetic res…

重空穴掺杂Ba0.1K 0.9Fe 2As 2中Lifshitz转变可能出现的节超导能隙

Possible nodal superconducting gap emerging at the Lifshitz transition in heavily hole-doped Ba0.1K0.9Fe2As2

利用高能量分辨率的ARPES方法研究了过掺杂Ba_（0.1）K_（0.9）Fe_2As_2（Tc = 9K）的晶体结构.这种材料的费米表面拓扑结构与KFe2As2相似，与掺杂量稍低的Ba0.3K0.7Fe2As2不同，这意味着在x=0.7和x=0.9之间发生了Lifshitz跃迁。尽管在出现的偏离M中心的费米面袋瓣尖端发现了一个垂直节点，但超导能隙结构与Ba 0.3K 0.7Fe 2As 2的超导能隙结构相似，表明配对相互作用不是由费米面拓扑结构驱动的。

用~（75）NQR和Specific Heat研究重空穴掺杂超导体KFe2As2中可能的线结多能隙超导性

Possible Multiple Gap Superconductivity with Line Nodes in Heavily Hole-Doped Superconductor KFe2As2 Studied by 75As-NQR and Specific Heat

报道了重空穴掺杂超导体KFe_2As_2（Tc = 3.5K）的~（75）As核四极共振（NQR）和比热测量结果。超导态的自旋-晶格弛豫速率1/T1表现出相当平缓的温度依赖性，在Tc以下没有相干峰。准粒子比热C_QP/T在低于Tc时有很小的比热跃变，约为电子比热系数的30%。此外，在最低测量温度T = 0.4 K \simeq Tc/10时，还存在低能准粒子激发.这些1/T1和C_QP/T的温度依赖性可以用多节超导能隙方案来解释，而不是简单能隙分析中的多个全能隙s_ \pm波方案。

Crystalline anisotropy induces a second antiferromagnetic phase in the absence of SDW in the heavily hydrogen-doped LaFeAsO$_{1-x}$H$_x$ $(x\sim0.5 )$

Electronic and magnetic properties of the heavily H-doped LaFeAsO$_{1-x}$H$_x$ $(x\sim0.5 )$ were studied in the framework of the density functional theory combined with the dynamical mean field theory (DFT+DMFT). We found a stripe-like-ordered structure of hydrogen and oxygen atoms, as a ground state, with the same configuration as the antiferromagnetic (AF) order. The new configuration could explain the existing experimental results related to the heavily H-doped LaFeAsO$_{1-x}$H$_x$, such as an in-plane electronic anisotropy and a non-uniform magnetic behavior. A significant anisotropy was …

Na掺杂Ca2CuO2Cl2单晶的角分辨光电子能谱：重欠掺杂超导体中磁性绝缘体的指纹

Angle-resolved photoemission spectroscopy of Na-doped Ca2CuO2Cl2 single crystals: Fingerprints of a magnetic insulator in a heavily underdoped superconductor

首次在高压下成功生长的四元Ca（1.9）Na（0.1）CuO（2）Cl（2）单晶的角分辨光电子能谱实验揭示了从反铁磁体到高温超导体的电子演化过程。在这种低掺杂的超导体中，我们发现了母体绝缘体的清晰指纹：阴影带和大的赝能隙。这些观察结果很可能被描述为“化学势位移”，这与从原型La（2-x）Sr（x）CuO（4）中了解到的“钉扎化学势”的流行观点形成鲜明对比，表明通往高Tc超导体的途径并不独特。

Signature of high Tc around 25K in higher quality heavily boron-doped diamond

Diamond has outstanding physical properties: the hardest known material, a wide band gap, the highest thermal conductivity, and a very high Debye temperature. In 2004, Ekimov et al. discovered that heavily boron-doped (B-doped) diamond becomes a superconductor around 4 K. Our group successfully controlled the boron concentration and synthesized homoepitaxially grown superconducting diamond films by a CVD method. By CVD method, we found that superconductivity appears when the boron concentration (nB) exceeds a metal-insulator transition concentration of 3.0x10^20 cm^-3 and its Tczero increases …

Extreme in-plane upper critical magnetic fields of heavily doped quasi-two-dimensional transition metal dichalcogenides

Extreme in-plane upper critical magnetic fields $B_{c2//ab}$ strongly violating the Pauli paramagnetic limit have been observed in the misfit layer $(LaSe)_{1.14}(NbSe_2)$ and $(LaSe)_{1.14}(NbSe_2)_2$ single crystals with $T_c$ = 1.23 K and 5.7 K, respectively. The crystals show a two-dimensional to three-dimensional transition at temperatures slightly below $T_c$ with an upturn in the temperature dependence of $B_{c2//ab}$, a temperature dependent huge superconducting anisotropy and a cusplike behavior of the angular dependence of $B_{c2}$. Both misfits are characterized by a strong charge t…

最佳电子掺杂的Nd_{1.85} Ce_{0.15} CuO $_{4-y}体材料中近各向同性s波带隙的非生物学证据

Unambiguous evidence for nearly isotropic s-wave gap in the bulk of optimally electron-doped Nd_{1.85}Ce_{0.15}CuO$_{4-y}

我们解决了一个重要的问题，无论是体敏感的数据的拉曼散射，光学电导率，磁穿透深度，定向点接触隧穿光谱，并在最佳的电子掺杂Nd_{1.85} Ce_{0.15} CuO_{4-y}的超导对断裂效应支持无节点的s波或d波超导能隙。我们数值计算拉曼强度，定向点接触隧穿光谱，和s-wave和d-wave间隙对称性方面的双破效应。我们发现，所有这些体积敏感的数据是在定量协议与近各向同性的s波间隙。T_{c}几乎与剩余电阻率无关的事实排除了任何d波间隙对称性。

重空穴掺杂Ba1-xKxFe2As2中空穴袋间符号反转的超导能隙

Superconducting gap with sign reversal between hole pockets in heavily hole-doped Ba1-xKxFe2As2

为了深入了解铁磷族元素化物的非常规超导性，没有电子口袋，我们测量了重空穴掺杂制度的Ba $_{1-x}$ K $_x$ Fe $_2$ As $_2$的热导率$κ$和穿透深度$λ$。剩余热导率$(κ/T)_{T \rightarrow 0\,{\rm K}}$和$λ$的$T$依赖性一致地表明在$x=0.76$处的完全带隙超导性和在较高空穴浓度处的（线）节超导性。在低温下的$\fracκ{T}\cdot T_c|_{T \rightarrow 0\,{\rm K}}$和$\frac{dλ}{d(T/T_c)}$的大小，这两者都是由低能量激发的性质决定的，表现出非常不寻常的非单调x依赖性。这些结果表明，在一个狭窄的掺杂范围内的节点特性的显着变化，表明掺杂交叉的s波状态之间的间隙函数与$Γ$中心的空穴袋之间的符号反转和没有。

重掺杂石墨烯的电子结构：外来原子态的作用

Electronic structure of heavily-doped graphene: the role of foreign atom states

利用密度泛函理论计算了掺杂原子对石墨烯电子结构的影响。我们证明，随着电荷转移到石墨烯层的增加，原始石墨烯片的能带结构受到很大影响。当Ca原子以CaC $_{6}$化学计量沉积在石墨烯上时，这特别相关。与超导石墨夹层化合物中发生的情况类似，Ca带出现在费米能级。其与C态的杂化在费米能级以下的$π^{*}$带之一中产生强非线性，其能量与石墨烯E $_{2g}$声子频率相当。这种强的非线性，而不是manybody效应，如先前提出的，解释了大的和各向异性的值的表观电子-声子耦合角分辨光电发射测量。

重掺杂块状单晶金刚石与石墨烯/金刚石异质结构中的超导性和金属行为

Superconductivity and metallic behavior in heavily doped bulk single crystal diamond and graphene/diamond heterostructure

该研究通过硼氮共掺杂制备高载流子浓度单晶超导金刚石，并揭示迁移率调控下的超导—金属转变，还利用石墨烯/金刚石异质结构使单层石墨烯超导。

电子掺杂铜氧化物超导体的角分辨光电子能谱：各向同性的电子-声子耦合

Angle-resolved photoemission spectroscopy of electron-doped cuprate superconductors: Isotropic electron-phonon coupling

我们对电子掺杂的铜酸盐超导体Sm_（2-x）CexCuO_4（x=0.10，0.15，0.18），Nd_（2-x）CexCuO_4（x=0.15）和Eu_（2-x）CexCuO_4（x=0.15）进行了高分辨角分辨光电子能谱（ARPES）研究。由于电子-玻色子模耦合，电子去除自能的虚部呈现阶梯状特征。的阶梯状功能被视为沿节点和反节点的方向，但在50和70毫电子伏的能量，分别独立的掺杂和稀土元素。这样的能量尺度可以理解为是由于半呼吸和全呼吸模式声子的优先耦合，揭示了扭结结构的声子起源。从自能估计的电子-声子耦合常数λ与掺杂和动量大致无关。的各向同性性质的λ进行了讨论，在比较与空穴掺杂的情况下，存在一个强的各向异性。

重过掺杂LaFeAsO-based超导体中反号s（+-）波库珀对态的相干效应：~（75）As核四极共振

Coherence Effect of Sign-Reversing s(+-)-wave Cooper Pair State in Heavily Overdoped LaFeAsO-based Superconductor: 75As-Nuclear Quadrupole Resonance

用~（75）As-核四极共振（NQR）方法研究了重电子掺杂LaFeAsO_（1-x）F_x（La_（1111））（Tc=5 K）晶体。核自旋弛豫速率（1/T1）测量表明，在电子过掺杂的情况下，Hebel-Slichter（HS）峰部分恢复，此时空穴和电子费米面（FS）的嵌套条件明显变差.这是在与最佳掺杂的La 1111与Tc=28 K，其中缺乏HS峰的报告先前的结果相反。结果表明，通过电子过掺杂，几乎消失的空穴FS强烈抑制了空穴和电子FS之间的带间散射。我们的研究结果强烈地表明，在不同的FS上的间隙函数的符号反转，即s（+-）波状态是实现在La 1111化合物。我们注意到，带间散射嵌套FS是必不可少的稳定的s（+-）波状态，并提高Tc到28 K的LaFeAsO基超导体。

高临界温度s±波超导性在重电子掺杂无限层镍酸盐中的可能性理论研究

Theoretical study on the possibility of high $T_c$ s$\pm$-wave superconductivity in the heavily hole-doped infinite layer nickelates

该研究探讨了在重电子掺杂无限层镍酸盐中实现高临界温度s±波超导性的可能性，通过电子构型和能带相互作用分析，发现超导性增强源于d_{x²−y²}带与其他轨道的能量偏移。

压力对Co掺杂NaFeAs超导性能的影响

Pressure effects on superconducting properties of single-crystalline Co doped NaFeAs

外压下的电阻率和磁化率的测量进行单晶NaFe 1-xCoxAs（x=0，0.01，0.028，0.075，0.109）。在欠掺杂和最佳掺杂的NaFe 1-xCoxAs中，由压力增强的最大Tc是相同的，高达31 K。x = 0.075的过掺杂样品也表现出对Tc的正压力效应，在2.3GPa的压力下，Tc提高了13 K。与Ba（Fe_（1-x）Co_x）_2As_2不同，所有样品都表现出较大的超导电性正压力系数。然而，在重过掺杂的非超导NaFe 0.891Co 0.109As中，压力不能诱导超导电性。这些结果提供了证据，超导和重过掺杂的非超导NaFe 1-xCoxAs之间的电子结构有很大的不同，与角分辨光电子能谱的观察是一致的。

重掺杂石墨烯中（d+id）波超导态的缺陷

Defects in the (d+id)-wave superconducting state in heavily doped graphene

一个手征时间反转对称性破缺（d+id）波超导态很可能出现在石墨烯掺杂接近范霍夫奇点。由于重掺杂程序预计将引入缺陷，我们在这里研究的（d+id）波超导状态在范霍夫奇点的微观缺陷的影响。我们发现，虽然超导秩序减少附近的缺陷，（d+id）波状态保持不变，并恢复在指数的方式远离缺陷。恢复长度被发现是一个晶格常数弱耦合的顺序。这与常规s波状态的恢复长度相当，表明非常规（d+id）波状态对缺陷具有相当的弹性。此外，我们发现一个单一的网站缺陷和更广泛的缺陷，如双空位之间没有显着的变化。虽然（d+id）波状态是完全带隙的，我们也表明，缺陷引入本地化的midgap状态与非零能量，这应该是通过扫描探针实验访问。

Specific heat和超导掺硼碳化硅的电子态

Specific heat and electronic states of superconducting boron-doped silicon carbide

2004年在重掺硼半导体杂质半导体金刚石（C：B）和2006年在硅（Si：B）中发现的超导电性重新引起了人们对杂质半导体超导态物理的兴趣。最近，我们发现在密切相关的“混合”系统重掺硼碳化硅（SiC：B）的超导性。有趣的是，后一种化合物是I型超导体，而上述两种材料是II型超导体。在本文中，我们提出了一个广泛的分析，我们最近的比热研究，以及能带结构和预期的费米面。我们观察到在超导状态下的电子比热表观的二次温度依赖性。可能的原因是节点间隙结构或由于样品的非超导部分而产生的剩余态密度。在Ginzburg-Landau框架下估计了基本的超导参数。我们比较和讨论我们的结果与那些报道的C：B和Si：B。最后，我们评论了SiC：B与两种“母体”材料C：B和Si：B相比，其超导电性差异的可能来源。

掺铝超导碳化硅的Specific heat

Specific heat of aluminium-doped superconducting silicon carbide

在重掺硼的金刚石、硅和碳化硅中发现的超导电性重新引起了人们对掺杂电荷载流子的宽禁带半导体的基态的兴趣。最近，碳化硅中的铝掺杂成功地产生了金属相，在高铝浓度下，超导性出现。在这里，我们提出了一个比热研究超导铝掺杂碳化硅。我们观察到一个明显的跳跃异常的超导转变温度为1.5 K，表明掺铝碳化硅是一个大块超导体。跳跃异常的分析表明，BCS类声子介导的超导在这个系统中。

Quasi-isotropic orbital magnetoresistance in lightly doped SrTiO$_{3}$

A magnetic field parallel to an electrical current does not produce a Lorentz force on the charge carriers. Therefore, orbital longitudinal magnetoresistance is unexpected. Here we report on the observation of a large and non saturating magnetoresistance in lightly doped SrTiO$_{3-x}$ independent of the relative orientation of current and magnetic field. We show that this quasi-isotropic magnetoresistance can be explained if the carrier mobility along all orientations smoothly decreases with magnetic field. This anomalous regime is restricted to low concentrations when the dipolar correlation …

Breakdown of single spin-fluid model in heavily hole-doped superconductor CsFe2As2

Although Fe-based superconductors are multiorbital correlated electronic systems, previous nuclei magnetic resonance (NMR) measurement suggests that a single spin-fluid model is sufficient to describe its spin behavior. Here, we firstly observed the breakdown of single spin-fluid model in a heavily hole-doped Fe-based superconductor CsFe2As2 by site-selective NMR measurement. At high temperature regime, both of Knight shift and nuclei spin-lattice relaxation at 133Cs and 75As nuclei exhibit distinct temperature-dependent behavior, suggesting the breakdown of single spin-fluid model in CsFe2As2…

Doping evolution of the superconducting gap structure in heavily hole-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$: heat transport study

We performed systematic thermal conductivity measurements on heavily hole-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$ single crystals with 0.747 $\leq x \leq$ 0.974. At $x$ = 0.747, the $κ_0/T$ is negligible, indicating nodeless superconducting gap. A small residual linear term $κ_0/T$ ($\approx$ 0.035 mW/K$^2$ cm) appears at $x$ = 0.826, and it increases slowly up to $x$ = 0.974, followed by a drastic increase of more than 20 times to the pure KFe$_2$As$_2$ ($x$ = 1.0). This doping dependence of $κ_0/T$ clearly shows that the nodal gap appears near $x = 0.8$, likely associated with the change of Fermi …

Competing electronic orders on a heavily doped honeycomb lattice with enhanced exchange coupling

Motivated by recent discovery of correlated insulating and superconducting behavior in twisted bilayer graphene, we revisit graphene's honeycomb lattice doped close to the van Hove singularity, using the truncated unity functional renormalization group approach. We consider an extended Hubbard model on the honeycomb lattice including on-site and nearest-neighbor Coulomb repulsions, and nearest-neighbor ferromagnetic exchange and pair hopping interactions. By varying the strength of the nearest-neighbor exchange coupling and Coulomb repulsion as free parameters, we present rich ground-state pha…

空穴过掺杂超导体KFe2As2中的无公度自旋涨落

Incommensurate spin fluctuations in hole-overdoped superconductor KFe2As2

重空穴过掺杂超导KFe $_2$ As $_2$的中子散射研究揭示了在[$π(1\pm2δ$），0]处定义良好的低能无公度自旋涨落，其中$δ$ = 0.16。该无公度结构不同于先前在低能量下在电子掺杂的$A$ Fe $_2$ As $_2$（$A$ = Ba、Ca或Sr）中观察到的公度峰。峰分裂的方向垂直于在Fe（Te，Se）或Ba（Fe，Co）$_2$ As $_2$中观察到的方向。能带结构计算表明，带间散射周围的$Γ$和X点的起源，这个不相称的峰。峰分裂的垂直方向可以在多轨道能带结构的框架内理解。结果表明，空穴掺杂样品中的自旋涨落比电子掺杂样品中的自旋涨落更强，这可能是重空穴掺杂样品中出现超导电性的原因.