N ov 2 00 1 SPIN COHERENT - STATE PATH INTEGRALS AND THE INSTANTON CALCULUS ANUPAM GARG
نویسنده
چکیده
We use an instanton approximation to the continuous-time spin coherentstate path integral to obtain the tunnel splitting of classically degenerate ground states. We show that provided the fluctuation determinant is carefully evaluated, the path integral expression is accurate to order O(1/j). We apply the method to the LMG model and to the molecular magnet Fe8 in a transverse field. This paper is dedicated to the memory of Victor Belinicher, who was lost when Siberia Airlines flight 1812 was shot down over the Black Sea, Oct 4th 2001. Victor made many contributions to physics, in particular to the spin tunneling problem. PACS numbers: 03.65.Ca, 03.65.Bz Typeset using REVTEX 2
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