Regular Article

Finite temperature phase transition in the two-dimensional Coulomb glass at low disorders

¹ Department of Physics, Jamia Millia Islamia, New Delhi 110025, India
² Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida, Uttar Pradesh, India

^a Present address: Indian Institute of Science Education and Research Mohali, Sector 81, S.A.S. Nagar, Manauli 140306, India.
^b e-mail: vikasm76@gmail.com

Received: 4 January 2019
Received in final form: 4 April 2019
Published online: 3 July 2019

Abstract

We present numerical evidence using Monte Carlo simulations of finite temperature phase transition in two dimensional Coulomb Glass lattice model with random site energies at half-filling. For the disorder strengths (W) studied in this paper, we find the existence of charge-ordered phase (COP) below the critical temperature (T_c(W)). Also, the probability distribution of staggered magnetization calculated at each W shows a two-peak structure at their respective critical temperature. Thus the phase transition from fluid to COP as a function of temperature is second order for all W. We find no evidence of a spin glass phase between a fluid and the COP. Further, we have used finite-size scaling analysis to calculate the critical exponents. The critical exponents at zero disorder are different from the one found at finite disorders, which indicates that the disorder is a relevant parameter here. The critical exponent for correlation length ν increases and T_c decreases with increasing disorder. Similar behaviour for ν was seen in the work of Overlin et al. for three dimensional Coulomb Glass model with a positional disorder. Our study also shows that other critical exponents are also a function of disorder.