Penson-Kolb模型中η对超导的热力学和电磁学性质
Thermodynamic and electromagnetic properties of the eta-pairing superconductivity in the Penson-Kolb model
摘要：
本文研究了Penson-Kolb（PK）模型的热力学和电磁学性质，紧束缚模型的费米子粒子与对跳跃相互作用$J$。我们重点讨论令人排斥的$J$的情况（即，$J<0$），其可以用库珀对质心动量$\vec{q}=\vec{Q}$、$\vec{Q}=(π/a$、$π/a$、\ldots）稳定η配对超导性。对几种$d$维超立方晶格：$d=2$（正方形晶格，SQ），$d=3$（简单立方晶格）和$d=\infty$超立方晶格（对于任意粒子浓度$0<n<2$和温度$T$）进行了数值计算.基态$J$与$n$相图和交叉的玻色-爱因斯坦凝聚制度进行了分析和超流特性的演变内（对称性破缺）的Hartree-Fock近似（HFA）检查。临界场，相干长度，伦敦穿透深度，和金斯堡比确定在$T=0$和$T>0$作为$n$和配对强度的函数。分析了Fock项对基态相界和所选PK模型特性的影响，并研究了相位涨落对η-配对超导性的影响。在Kosterlitz-plasterless情形下，对$d=2$ SQ晶格的临界温度$T_{KT} $进行了估算，并与HFA得到的临界温度$T_c$进行了比较.我们还确定了温度$T_m$在两个准粒子带之间的最小间隙消失在η相。我们对排斥性$J$的结果与先前对具有吸引性$J$的PK模型（即，$J>0$）。
英文摘要：
In the paper, we study the thermodynamic and electromagnetic properties of the Penson-Kolb (PK) model, i.e., the tight-binding model for fermionic particles with the pair-hopping interaction $J$. We focus on the case of repulsive $J$ (i.e., $J<0$), which can stabilize the eta-pairing superconductivity with Cooper-pair center-of-mass momentum $\vec{q}=\vec{Q}$, $\vec{Q}=(π/a$,$π/a$,\ldots). Numerical calculations are performed for several $d$-dimensional hypercubic lattices: $d=2$ (the square lattice, SQ), $d=3$ (the simple cubic lattice) and $d=\infty$ hypercubic lattice (for arbitrary particle concentration $0<n<2$ and temperature $T$). The ground state $J$ versus $n$ phase diagrams and the crossover to the Bose-Einstein condensation regime are analyzed and the evolution of the superfluid characteristics are examined within the (broken symmetry) Hartree-Fock approximation (HFA). The critical fields, the coherence length, the London penetration depth, and the Ginzburg ratio are determined at $T=0$ and $T>0$ as a function of $n$ and pairing strength. The analysis of the effects of the Fock term on the ground state phase boundaries and on selected PK model characteristics is performed as well as the influence of the phase fluctuations on the eta-pairing superconductivity is investigated. Within the Kosterlitz-Thouless scenario, the critical temperatures $T_{KT} $ are estimated for $d=2$ SQ lattice and compared with the critical temperature $T_c$ obtained from HFA. We also determine the temperature $T_m$ at which minimal gap between two quasiparticle bands vanishes in the eta-phase. Our results for repulsive $J$ are contrasted with those found earlier for the PK model with attractive $J$ (i.e., with $J>0$).
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