eprintid: 10185457
rev_number: 6
eprint_status: archive
userid: 699
dir: disk0/10/18/54/57
datestamp: 2024-01-16 11:43:34
lastmod: 2024-01-16 11:43:34
status_changed: 2024-01-16 11:43:34
type: article
metadata_visibility: show
sword_depositor: 699
creators_name: Saheli, Shahnam Ghanbari
creators_name: Lin, Jennifer
creators_name: Hu, Huanzhi
creators_name: Krüger, Frank
title: Majorana-fermion mean field theories of Kitaev quantum spin liquids
ispublished: pub
divisions: UCL
divisions: B04
divisions: C06
divisions: F60
divisions: F64
note: © 2024 American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0/).
abstract: We determine the phase diagrams of anisotropic Kitaev-Heisenberg models on the honeycomb lattice using parton mean-field theories based on different Majorana fermion representations of the 
S = 1/2 spin operators. First, we use a two-dimensional Jordan-Wigner transformation (JWT) involving a semi-infinite snake string operator. To ensure that the fermionized Hamiltonian remains local, we consider the limit of extreme Ising exchange anisotropy in the Heisenberg sector. Second, we use the conventional Kitaev representation in terms of four Majorana fermions subject to local constraints, which we enforce through Lagrange multipliers. For both representations, we self-consistently decouple the interaction terms in the bond and magnetization channels and determine the phase diagrams as a function of the anisotropy of the Kitaev couplings and the relative strength of the Ising exchange. While both mean-field theories produce identical phase boundaries for the topological phase transition between the gapless and gapped Kitaev quantum spin liquids, the JWT fails to correctly describe the magnetic instability and finite-temperature behavior. Our results show that the magnetic phase transition is first order at low temperatures but becomes continuous above a certain temperature. At this energy scale, we also observe a finite-temperature crossover on the quantum-spin-liquid side, from a fractionalized paramagnet at low temperatures, in which gapped flux excitations are frozen out, to a conventional paramagnet at high temperatures.
date: 2024-01
date_type: published
publisher: American Physical Society (APS)
official_url: http://dx.doi.org/10.1103/physrevb.109.014407
oa_status: green
full_text_type: pub
language: eng
primo: open
primo_central: open_green
verified: verified_manual
elements_id: 2139450
doi: 10.1103/physrevb.109.014407
lyricists_name: Hu, Huanzhi
lyricists_name: Kruger, Frank
lyricists_id: HHUAX88
lyricists_id: FKRUG35
actors_name: Kruger, Frank
actors_id: FKRUG35
actors_role: owner
full_text_status: public
publication: Physical Review B
volume: 109
number: 1
article_number: 014407
citation:        Saheli, Shahnam Ghanbari;    Lin, Jennifer;    Hu, Huanzhi;    Krüger, Frank;      (2024)    Majorana-fermion mean field theories of Kitaev quantum spin liquids.                   Physical Review B , 109  (1)    , Article 014407.  10.1103/physrevb.109.014407 <https://doi.org/10.1103/physrevb.109.014407>.       Green open access   
 
document_url: https://discovery.ucl.ac.uk/id/eprint/10185457/1/KitaevIsing.pdf