The theory of hole superconductivity proposes that superconductivity is driven by lowering of quantum kinetic energy and is associated with expansion of electronic orbits and expulsion of negative charge from the interior to the surface of superconductors and beyond. This physics provides a dynamical explanation of the Meissner effect. Here we propose that similar physics takes place in superfluid helium 4. Experimental manifestations of this physics in $^4He$ are the negative thermal expansion of $^4He$ below the $λ$ point and the "Onnes effect", the fact that superfluid helium will creep up the walls of the container and escape to the exterior. The Onnes effect and the Meissner effect are proposed to originate in macroscopic zero point rotational motion of the superfluids. It is proposed that this physics indicates a fundamental inadequacy of conventional quantum mechanics.
The transition mechanism of metal-insulator in metal oxides is discussed in detail, which is a part of the mechanism of superconductivity. Through the study of magic angle twisted bilayer graphene superconductor and other new findings on superconductivity, we further demonstrate that the physical mechanism of superconductivity proposed in Part I is the only correct way to handle the properties of superconductivity in various materials. We propose that superfluid helium consists of normal liquid helium mixed with high-energy helium atoms. Based on this new model, all peculiar features discovere…
A consistent microscopic theory of pseudogap phenomena and novel Bose-liquid superconductivity (superfluidity) is presented, based on the fact that in high-$T_c$ cuprates and related systems the energy $\varepsilon_A$ of the effective attraction between fermions is comparable with their Fermi energy $\varepsilon_F$ and the bosonic Cooper pairs are formed above $T_c$ and then a part of such Cooper pairs condense into a Bose superfluid at $T_c$. High-$T_c$ cuprates and other systems with low Fermi energies ($\varepsilon_F\sim\varepsilon_A$) are bosonic superconductors/superfluids and exhibit pse…
We utilize the Hubbard model to demonstrate that doping of the antiferromagnetic parent compounds of cuprate superconductors stabilizes a spin liquid state. Superconductivity in such a state emerges due to the spin-orbit coupling between charge current and superfluidity of spinon condensate, resulting in a chiral relation between the order parameter phase gradient and supercurrent. We propose simple experimental tests for the presented mechanism.
We show that two phenomena of superfluidity, superfluidity of weakly interacting bosons and superconductivity of the BCS model, are unified using the collective mode arising from the Berry connection for many-body wave functions. The superfluidity is attributed to the presence of this mode, which is stabilized by the interaction between particles that causes fluctuations of the number of particles participating in it. It is suggested that the existence of this collective mode and its stabilization is more fundamental to the occurrence of superconductivity than the electron-pair formation.
Designer 2D materials where the constituent layers are not aligned may result in band structures with dispersionless, "flat" bands. Twisted bilayer graphene has been found to show correlated phases as well as superconductivity related to such flat bands. In parallel, theory work has discovered that superconductivity and superfluidity is determined by the quantum geometry and topology of the band structure. These recent key developments are merging to a flourishing research topic: understanding the possible connection and ramifications of quantum geometry on the induced superconductivity and su…
We introduce a new and general mechanism for superconductivity in Fermi systems with strong repulsive interaction. Because kinetic terms are small compared to the bare repulsion, the dynamic of charge carriers is constrained by the the presence of other nearby carriers. By treating kinetic terms as a perturbation around the atomic limit, we show that pairing can be induced by correlated multi-particle tunneling processes that favor two itinerant carriers to be close together. Our analytically-controlled theory provides a quantitative formula relating $T_c$ to microscopic parameters, with maxim…
"Fragile superconductivity": a kinetic glass transition in the vortex matter of the high-temperature superconductor YBa2Cu3O7-d
在自然界中发现的许多不同种类的玻璃态中，自旋玻璃和结构玻璃（例如普通窗玻璃）可能受到最多的关注。关于玻璃态的中心问题之一是“玻璃”是否是不同于“液体”相的热力学相。据信，这实际上可能是自旋玻璃的情况，而结构玻璃中的玻璃化转变似乎主要是动力学性质的。然而，过冷结构液体表现出广泛的行为，可以使用Angell的“强-脆弱”方案进行分类，其中术语“强”和“脆弱”分别指Arrhenius和高度非Arrhenius松弛行为。对于极其脆弱的液体，不能排除玻璃化转变的热力学起源。然而，缺乏对导致不同程度的脆弱性和影响动力学玻璃化转变的复杂性的微观理解。此外，不同种类的玻璃态（自旋、结构等）之间的联系（如果有的话）还不清楚在这里，我们研究了一种新型的物质，即在高温超导体（HTSC）YBa 2 Cu 3 Ox的涡旋物质的玻璃态行为。
Non-equilibrium Enhancement of Cooper Pairing in Cold Fermion Systems
本文类比Eliashberg [G. M. Eliashberg，在“非平衡超导性”中，由D. N. Langenberg和A. I. Larkin（North-Holland，New York，1986）]关于微波对超导性的增强。通过由于与玻色子浴的热接触和/或蒸发冷却引起的热损失平衡的费米子的光学激发使得能够存在稳定的非平衡态。这种状态表现为准粒子谱向更高能量的移动，这种效应有效地提高了配对转变温度。作为一个例子，我们计算了有效的增强库珀配对和超流性的正常和超流相的混合物的Rb和Li在小偏离平衡的限制。有人认为，在实验中所希望的效果并不限于这样的小扰动和有效的配对温度的提高可能是相当大的。
The Ginzburg-Landau (GL) effective theory is a useful tool to study a superconductivity or superfluidity near the critical temperature, and usually the expansion up to the 4th order in terms of order parameters is sufficient for the description of the second-order phase transition. In this paper, we discuss the GL equation for the neutron $^{3}P_{2}$ superfluidity relevant for interior of neutron stars. We derive the GL expansion up to the 8th order in the condensates and find that this order is necessary for the system to have the unique ground state, unlike the ordinary cases. Starting from …
