Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 7: Transport: Quantum Coherence and Quantum Information Systems – Theory (jointly with HL, MA)

TT 7.13: Vortrag

Montag, 16. März 2015, 12:45–13:00, H 3005

Spin dynamics using the Majorana representation: validity, path integral and higher correlators — •Pablo Schad¹, Boris N. Narozhny^1,2, Gerd Schön³, Yuriy Makhlin^4,5, and Alexander Shnirman¹ — ¹Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany — ²National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe shosse 31, 115409 Moscow, Russia — ³Institut für Theoretische Festkörperphysik und Institut für Nanotechnologie, Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany — ⁴Landau Institute for Theoretical Physics, acad. Semyonov av., 1a, 142432, Chernogolovka, Russia — ⁵Moscow Institute of Physics and Technology, 141700, Dolgoprudny, Russia

We present a method to calculate higher spin correlators via the Majorana fermion representation of spin operators. We show explicitly that the Majorana representation does not require any projection procedure. Previously found identities [1,2] between spin and Majorana fermion correlation functions are extended. As an example we consider a spin-1/2 coupled to an isotropic, ohmic bath. We formulate a path-integral approach, which is valid at B=0 in contrast to perturbation theory, find the saddle-point solution and discuss fluctuations. We demonstrate that spin correlators in the high-temperature regime can be obtained using saddle-point Green’s functions.

[1] A. Shnirman and Y. Makhlin,

Phys. Rev. Lett. 91, 207204 (2003).

[2] W. Mao, P. Coleman, C. Hooley, and D. Langreth,

Phys. Rev. Lett. 91, 207203 (2003).