Thermally enhanced Majorana-mediated spin transport in the Kitaev model

• Main Authors: Koga, A. (Author), Murakami, Y. (Author), Taguchi, H. (Author)
• Format: Article
• Language: English
• Published: American Physical Society 2022
• Subjects: Excited states; Ground state; Kitaev model; Majorana; Quantum chemistry; Quantum spin; Quantum state; Spin excitation; Spin fluctuations; Spin moments; Spin transport; Thermal; Thermal fluctuations; Time dependent
• Online Access: View Fulltext in Publisher

 We study how stable the Majorana-mediated spin transport in a quantum spin Kitaev model is against thermal fluctuations. Using the time-dependent thermal pure quantum state method, we examine finite-temperature spin dynamics in the Kitaev model. The model exhibits two characteristic temperatures, TL and TH, which correspond to energy scales of the local flux and the itinerant Majorana fermion, respectively. At low temperatures (T TL), an almost flux-free state is realized, and the spin excitation propagates in a similar way to that for the ground state. Namely, after the magnetic pulse is introduced at one of the edges, the itinerant Majorana fermions propagate the spin excitations even through the quantum spin liquid state region, and oscillations in the spin moment appear in the other edge with a tiny magnetic field. When T∼TL, larger oscillations in the spin moments are induced in the other edge, compared with the results at the ground state. At higher temperatures, excited Z2 fluxes disturb the coherent motion of the itinerant Majorana fermions, which suppresses the spin propagation. Our results demonstrate a crucial role of thermal fluctuations in the Majorana-mediated spin transport. © 2022 American Physical Society.