Itinerant Spin Dynamics in Structures of ... - Jacobs University

Itinerant Spin Dynamics in Structures of ... - Jacobs University Itinerant Spin Dynamics in Structures of ... - Jacobs University

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Appendix E Summation over the Fermi Surface The Cooperon Hamiltonian in the 2D case is given by H c = τv 2 {〈cos 2 (ϕ)〉(Q+2m e a.S) 2 x +〈sin 2 (ϕ)〉(Q+2m e a.S) 2 y +4m 2 e γ Dv 2 〈cos 2 (ϕ)sin 2 (ϕ)〉(Q+2m e a.S) x .S x −4m 2 eγ D v 2 〈sin 2 (ϕ)cos 2 (ϕ)〉(Q+2m e a.S) y .S y +(2m 3 e γ Dv 2 ) 2 (〈cos 2 (ϕ)sin 4 (ϕ)〉Sx 2 +〈sin 2 (ϕ)cos 4 (ϕ)〉S 2 y)}, (E.1) with wave vector Q. We set m e ≡ 1, f 1 := 〈sin 2 (ϕ)〉, f 2 := 〈cos 2 (ϕ)〉, f 3 := 〈sin 2 (ϕ)cos 2 (ϕ)〉, f 4 := 〈sin 4 (ϕ)cos 2 (ϕ)〉, f 5 := 〈sin 2 (ϕ)cos 4 (ϕ)〉. (E.2) (E.3) (E.4) (E.5) (E.6) (E.7) Using the Matsubara trick we write ∫ 2π 0 dϕ 2π = 2 πN N∑ 1 √ 1− ( ) . (E.8) s 2 N s=1 148

Appendix E: Summation over the Fermi Surface 149 This gives us f 1 = 2 N−1 ∑ πN s=1 f 2 = 2 πN f 3 = 2 πN f 4 = 2 πN f 5 = 2 πN s 2 N √1− ( ) , (E.9) 2 s 2 N √ N∑ ( s ) 2, 1− (E.10) N s=1 N∑ ( s ) √ 2 ( s ) 2, 1− (E.11) N N s=1 N∑ ( s ) √ 4 ( s ) 2, 1− (E.12) N N s=1 N∑ s=1 Writing Eq.(E.1) in a compact way gives us Eq.(4.49). ( ( )3 s 2 ( s 2 2 1− . (E.13) N) N)

Appendix E: Summation over the Fermi Surface 149<br />

This gives us<br />

f 1 = 2 N−1<br />

∑<br />

πN<br />

s=1<br />

f 2 = 2<br />

πN<br />

f 3 = 2<br />

πN<br />

f 4 = 2<br />

πN<br />

f 5 = 2<br />

πN<br />

s 2<br />

N<br />

√1− ( ) , (E.9)<br />

2 s 2<br />

N<br />

√ N∑ ( s<br />

) 2,<br />

1−<br />

(E.10)<br />

N<br />

s=1<br />

N∑ ( s<br />

)<br />

√<br />

2 ( s<br />

) 2,<br />

1−<br />

(E.11)<br />

N N<br />

s=1<br />

N∑ ( s<br />

)<br />

√<br />

4 ( s<br />

) 2,<br />

1−<br />

(E.12)<br />

N N<br />

s=1<br />

N∑<br />

s=1<br />

Writ<strong>in</strong>g Eq.(E.1) <strong>in</strong> a compact way gives us Eq.(4.49).<br />

( ( )3<br />

s 2 ( s 2 2<br />

1− . (E.13)<br />

N)<br />

N)

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