Theoretical Studies on Many-Band Effects in Superconductivity by Using Renormalization Group Approach

2003 ◽  
Vol 17 (10n12) ◽  
pp. 423-431 ◽  
Author(s):  
Hidemi Nagao ◽  
Hiroyuki Kawabe ◽  
Sergei P. Kruchinin ◽  
Dirk Manske ◽  
Kizashi Yamaguchi
Keyword(s):  
Renormalization Group ◽  
Phase Diagrams ◽  
Electron Interaction ◽  
Band Model ◽  
Theoretical Studies ◽  
Group Approach ◽  
Renormalization Group Approach ◽  
Two Band Model

We present a renormalization equations for two-band superconductivity by using a two-band model and present phase diagrams for the two-band superconductivity. In the framework of two-band model, the present results predict that superconductivity appears, even if electron-electron interaction is positive. We discuss the possibility of a cooperative mechanism in the two-band superconductivity in relation to high-Tc superconductivity.

Superconductivity in Two-Band Model by Renormalization Group Approach

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3373-3376
Author(s):  
Hidemi Nagao ◽  
Hiroyuki Kawabe ◽  
Sergei P. Kruchinin ◽  
Kizashi Yamaguchi
Keyword(s):  
Renormalization Group ◽  
Gap Function ◽  
Superconducting Gap ◽  
Band Model ◽  
Group Approach ◽  
Renormalization Group Approach ◽  
Two Band Model

We investigate the superconductivity in a two-band model by using the renormalization group approach. We discuss the superconducting gap function in the two-band model.

The mixed spin-3/2 and spin-2 Blume-Capel model by renormalization group approach

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Karima El Kihel ◽  
Hasnae Saadi ◽  
Rachid Aharrouch ◽  
Abdelmoumen El Antari ◽  
Nabil Hachem ◽  
...  
Keyword(s):  
Renormalization Group ◽  
Phase Diagrams ◽  
Low Temperatures ◽  
Real Space ◽  
Group Approach ◽  
Content Type ◽  
First Order ◽  
Mixed Spin ◽  
Real Space Renormalization Group ◽  
Renormalization Group Approach

PurposeThe authors investigate the magnetic properties of a mixed spin-3/2 and spin-2 Blume-Capel model on square and cubic lattices with two different single-ion anisotropies.Design/methodology/approachTo study the critical behavior of a mixed spin-3/2 and spin-2 system, the authors have used a real space renormalization group approximation and specifically the Migdal-Kadanoff technique. The authors give the phase diagrams for two different cases: (1) on the (Δ/|J|, 1/|J|) plane with ΔA = ΔB = Δ, and (2) on the (ΔA/|J|, 1/|J|) and (ΔB/|J|, 1/|J|) planes for selected values of ΔB/|J| and ΔA/|J|, respectively.FindingsThe phase diagrams obtained show that the system exhibits both second- and first-order phase transitions as well as tricritical points for some values of the anisotropies. Moreover, using the variation of the free energy and its derivative at low temperatures, the authors have seen the appearance of first-order transitions at very low temperatures.Originality/valueFew investigations of mixed spin-3/2 and spin-2 systems with crystal field have been realized. For this reason, the authors use the renormalization group approach to complete the work done on these systems. In absence of an exact solution, this contributes to the synthesis of the approximation results on mixed spins models.

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