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The physics of spin-1/2 xy model with four site exchange interaction on the kagome lattice

The quantum spin liquid (QSL) state, proposed more than three decades ago by Fazekas and Anderson remains surprisingly elusive. Although recent experiments provide a strong evidence of their existence in the frustrated spin systems, the microscopic model for this state is still rare. | Journal of Science and Technology 54 (1A) (2016) 17-24 THE PHYSICS OF SPIN-1/2 XY MODEL WITH FOUR-SITE EXCHANGE INTERACTION ON THE KAGOME LATTICE Nguyen Thi Kim Oanh1, Pham Thanh Dai1, Dang Dinh Long1, 2, * 1 VNU-University of Engineering and Technology, 144 Xuan Thuy, Cau Giay, Hanoi 2 University of Ulsan, 93, Daehak-ro, Nam-gu, Ulsan, Korea * Email: longdd@gmail.com Received: 19 August 2015; Accepted for publication: 25 October 2015 ABSTRACT The quantum spin liquid (QSL) state, proposed more than three decades ago by Fazekas and Anderson remains surprisingly elusive. Although recent experiments provide a strong evidence of their existence in the frustrated spin systems, the microscopic model for this state is still rare. The extensive theoretical framework, developed over decades, continues to extend further motivated by these and other discoveries from large-scale computer simulations of a relatively small number of models. In this work, we discuss the physics of the ground-state phase diagram of a twodimensional Kagome lattice spin-1/2 XY model with a four-site ring-exchange interaction using quantum Monte Carlo simulation. We found the second order phase transition from superfluid state to a Z2 quantum spin liquid phase driven by the four-site ring exchange interaction. We have characterized the QSL by its vanishing order parameters such as the spin-spin structure factor, the plaquette-plaquette structure factor. Moreover, we have found the large anomalous exponent ηXY* ≈ 1.325 which belongs to a different universality class other than 3D XY universality class. There is no signal of supersolid phase intervening between the superfluid state and QSL state. Keywords: Quantum Spin Liquid, Kagome Lattice, Quantum Monte Carlo, Ring Exchange Model, critical exponents. 1. INTRODUCTION Although Fazekas and Anderson [1] proposed an idea of quantum spin liquid (QSL) state three decades ago, recent neutron scattering experiments on the spin-1/2 Kagome .