Speaker:

Peter Kopietz

Institution:

University of Frankfurt

Speaker Link:

Date:

Wednesday, October 10, 2018

Time:

4:00 pm

Location:

NS2 1201

**Abstract:**

We show that the generating functional of the time-ordered connected spin correlation functions of an arbitrary quantum spin system satisfies an exact renormalization group flow equation [1]. Formally, this flow equation resembles bosonic version of the so-called Wetterich equation. The SU(2) spin algebra is taken into account by integrating the renormalization group flow with a non-trivial initial condition. Our method is closely related to a diagrammatic approach to quantum spin systems developed many years ago in a seminal work by Vaks, Larkin, and Pikin [2]. As a first application, we show that our method gives the critical temperature of spin-S Ising models with high accuracy. We also discuss applications to quantum spin systems without long-range magnetc order.

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*[1] J. Krieg and P. Kopietz, arXiv:1807.02524*

[2] V. G. Vaks, A. I. Larkin, and S. A. Pikin, Sov. Phys. JETP {\bf{26}}, 188 (1968).

[2] V. G. Vaks, A. I. Larkin, and S. A. Pikin, Sov. Phys. JETP {\bf{26}}, 188 (1968).

Host:

Sasha Chernyshev