结果表明，超导金属间化合物MgB_2具有狭窄的、部分填充的“超导带”，其能带结构具有特殊对称性的Wannier函数。这一结果证实了以前对许多超导体和非超导体的能带结构的观察，表明超导性显然总是与这些超导带联系在一起的。这些发现被解释在一个非绝热扩展的海森堡模型的框架。在这个新的群论模型的相关系统，库珀对稳定的约束力在狭窄的超导带的非绝热机制。超导带中库珀对的形成是由所考虑的材料中能量最低的玻色子激发介导的，该材料携带晶体自旋角动量1 x h-巴。这些晶体自旋1玻色子被提出来确定该材料是传统的低Tc还是高Tc超导体。这种解释提供了电子-声子机制，进入BCS理论在传统的超导体。
英文摘要：
It is shown that the superconducting intermetallic compound MgB2 possesses a narrow, partly filled "superconducting band" with Wannier functions of special symmetry in its band structure. This result corroborates previous observations about the band structures of numerous superconductors and non-superconductors showing that evidently superconductivity is always connected with such superconducting bands. These findings are interpreted in the framework of a nonadiabatic extension of the Heisenberg model. Within this new group-theoretical model of correlated systems, Cooper pairs are stabilized by a nonadiabatic mechanism of constraining forces effective in narrow superconducting bands. The formation of Cooper pairs in a superconducting band is mediated by the energetically lowest boson excitations in the considered material that carry the crystal spin-angular momentum 1 x h-bar. These crystal-spin-1 bosons are proposed to determine whether the material is a conventional low-Tc or a high-Tc superconductor. This interpretation provides the electron-phonon mechanism that enters the BCS theory in conventional superconductors.
As shown in former papers, the nonadiabatic Heisenberg model presents a novel mechanism of Cooper pair formation generated by the strongly correlated atomic-like motion of the electrons in narrow, roughly half-filled "superconducting bands". These are energy bands represented by optimally localized spin-dependent Wannier functions adapted to the symmetry of the material under consideration. The formation of Cooper pairs is not the result of an attractive electron-electron interaction but can be described in terms of quantum mechanical constraining forces constraining the electrons to form Coop…
Strontium ruthenate (Sr$_2$RuO$_4$) has long been thought to host a spin-triplet chiral $p$-wave superconducting state. However, the singletlike response observed in recent spin-susceptibility measurements casts serious doubts on this pairing state. Together with the evidence for broken time-reversal symmetry and a jump in the shear modulus $c_{66}$ at the superconducting transition temperature, the available experiments point towards an even-parity chiral superconductor with $k_z(k_x\pm ik_y)$-like $E_g$ symmetry, which has consistently been dismissed based on the quasi-two-dimensional electr…
Stabilizing and Tuning Superconductivity in La$_3$Ni$_2$O$_{7-δ}$ Films: Oxygen Recycling Protocol Reveals Hole-Doping Analogue
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所凝聚态物理国家实验室）；University of Chinese Academy of Sciences（中国科学院大学）；Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences（中国科学院上海高等研究院上海同步辐射光源）；Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；Songshan Lake Materials Laboratory（松山湖材料实验室）
We show that the presence of Majorana zero modes (2D), and chiral-dispersing Majorana modes (3D), in the vortex cores of superconductors are neither sufficient nor necessary conditions for one to conclude the superconductivity is topologically non-trivial. We discuss the relevance of this result to the proximity-induced superconductivity, in the presence of magnetic field, on the surface of topological insulators.
Non-equilibrium superconductivity in driven alkali-doped fullerides
本文研究了碱金属掺杂富勒烯A $_3$ C $_{60}$中非平衡超导态的形成。在这些材料的超导性的最小三轨道模型中，最近从理论上证明了相互作用的轨道依赖性不平衡导致平衡态下超导性的增强[M. Kim等人Phys.Rev.B94，155152（2016）]。我们调查的动态响应的时间周期性调制的这种相互作用的不平衡，并表明，它导致形成的瞬态超导状态的生存远远超过平衡临界温度$T_c$。对于一个特定的调制频率范围内，我们发现，驱动降低超导性时，施加到超导状态低于$T_c$，而仍然诱导超导状态时，初始温度大于$T_c$。这些发现加强了相关的相互作用不平衡机制作为一个可能的解释最近的实验观察光诱导的超导电性在碱掺杂富勒烯。
We report the magnetoresistance in the novel spin-triplet superconductor UTe2 under pressure close to the critical pressure Pc, where the superconducting phase terminates, for field along the three a, b and c-axes in the orthorhombic structure. The superconducting phase for H // a-axis just below Pc shows a field-reentrant behavior due to the competition with the emergence of magnetic order at low fields. The upper critical field Hc2 for H // c-axis shows a quasi-vertical increase in the H-T phase diagram just below Pc, indicating that superconductivity is reinforced by the strong fluctuations…
The weak-coupling renormalization group method is an asymptotically exact method to find superconducting instabilities of a lattice model of correlated electrons. Here we extend it to spin-orbit coupled lattice systems and study the emerging superconducting phases of the Rashba-Hubbard model. Since Rashba type spin-orbit coupling breaks inversion symmetry, the arising superconducting phases may be a mixture of spin-singlet and spin-triplet states. We study the two-dimensional square lattice as a paradigm and discuss the symmetry properties of the arising spin-orbit coupled superconducting stat…
Chiral superconductivity from spin polarized Chern band in twisted MoTe$_2$
University of Tennessee, Knoxville（田纳西大学诺克斯维尔分校）；Tsinghua University（清华大学）；Max Planck Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）；Shanghai Jiao Tong University（上海交通大学）；Center for Integrated Nanotechnologies (CINT)（综合纳米技术中心）；Min H. Kao Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville（田纳西大学诺克斯维尔分校闵H. Kao电气与计算机工程系）
Recently superconductivity was discovered in the Kagome metal AV3Sb5 (A = K, Rb, and Cs), which has an ideal Kagome lattice of vanadium. These V-based superconductors also host charge density wave (CDW) and topological nontrivial band structure. Here we report the ultralow-temperature thermal conductivity and high pressure resistance measurements on CsV3Sb5 with Tc = 2.5 K, the highest among AV3Sb5. A finite residual linear term of thermal conductivity at zero magnetic field and its rapid increase in fields suggest nodal superconductivity. By applying pressure, the Tc of CsV3Sb5 increases firs…
The new superconductivity theory that attributes the $U(1)$ superconductivity phase to a Berry phase arising from many-body wave functions is applied to the circuit quantization for superconducting qubits. The phase-charge duality required for the occurrence of superconductivity in the standard theory becomes irrelevant in the new theory, and the absence of a dissipative quantum phase transition in Josephson junctions is explained. It is shown that a charge-decaying term leads to the compact phase description, and the appearance of Shapiro steps is explained without introducing normal current.
On mechanism of high-temperature superconductivity in hydrogen sulfide at 200 GPa: transition into superconducting anti-adiabatic state in coupling to H-vibrations
$^{119}$Sn-NMR investigations on superconducting Ca$_3$Ir$_4$Sn$_{13}$: Evidence for multigap superconductivity
利用$^{119}$ Sn核磁共振实验研究了Ca $_3$ Ir $_4$ Sn $_{13}$的体超导电性. BCS超导的自旋-晶格弛豫速率（$1/T_1$）有两个经典特征，即$T_c$之下的Hebel-Slichter相干峰和超导相的指数衰减。$^{119}$ Sn Knight位移在低于$T_c$时的显著降低表明自旋单重态超导性。自旋晶格弛豫速率（$1/T_1$）的温度依赖性令人信服地描述了多间隙各向同性超导带隙。目前的核磁共振实验没有看到任何迹象，增强自旋波动的正常状态。
Electron pairing by dispersive phonons in altermagnets: re-entrant superconductivity and continuous transition to finite momentum superconducting state
研究交错磁体中色散声子介导的电子配对，发现热声子散射抑制交错磁性，导致超导电性随温度重入，并在低温稳定 FFLO 有限动量超导态，无需 d 波配对。
Reentrant superconductivity has been observed in the candidate spin-triplet superconductor UTe$_2$ as a function of the magnetic field applied along the hard axis. Resistivity measurements have shown, a broadened superconducting transition appears near the minimal $T_c$, highlighting the importance of superconducting fluctuations in this regime. We present a phenomenological study assuming a field-driven first-order transition between two superconducting states. We show that with quenched randomness, inhomogeneity-enhanced superconducting fluctuations near the transition could naturally accoun…
Topological materials which are also superconducting are of great current interest, since they may exhibit a non-trivial topologically-mediated superconducting phase. Although there have been many reports of pressure-tuned or chemical-doping-induced superconductivity in a variety of topological materials, there have been few examples of intrinsic, ambient pressure superconductivity in a topological system having a stoichiometric composition. Here, we report that the pure intermetallic CaSn3 not only exhibits topological fermion properties but also has a superconducting phase at 1.178 K under a…
SrTiO$_3$ is a unique example of a system which exhibits both quantum paraelectricity and superconductivity. Thus, it is expected that the superconducting state is closely related to the intrinsic ferroelectric instability. Indeed, recent experiments suggest existence of a coexistent phase of superconductivity and ferroelectricity in Ca-substituted SrTiO$_3$. In this paper, we propose that SrTiO$_3$ can be a platform of the ferroelectric superconductivity, which is characterized by a ferroelectric transition in the superconducting state. By analyzing a multiorbital model for $t_{2g}$ electrons…
