The effect of intrinsic quantum fluctuations on the phase diagram of anisotropic dipolar magnets

by Mr. Tomer Dolberg

at Condensed Matter Seminar

Mon, 20 Jan 2020, 11:30
Sacta-Rashi Building for Physics (54), room 207


Anisotropic dipolar magnets are materials in which a strong anisotropic crystal-field potential results in an Ising-like ground state doublet that is well separated from the first excited state. They are thus ideal systems to study the Ising model. One such material is LiHoF4 which, under applied transverse magnetic field, is considered a good physical realization of the transverse field Ising model with dipolar interactions.
Results from previous studies, using various Monte Carlo techniques, show a persistent discrepancy with experimental results for the Bx-T phase diagram. Namely, in the low Bx regime, the experimental phase boundary separating the ferromagnetic and paramagnetic phases has a much smaller dependence on magnetic field in comparison to the theoretical predictions.
In this talk I will propose a mechanism which may account for the discrepancy.
Offdiagonal terms of the dipolar interaction, more dominant in the disordered paramagnetic phase, reduce the energy of the paramagnetic phase, and consequently reduce the critical temperature.
Using classical Monte Carlo simulations, in which we explicitly take the modification of the Ising states due to the offdiagonal terms into account, we show that the inclusion of these terms markedly reduces Tc at zero transverse field. We also show that the effect is diminished with increasing transverse field, suggesting a possible explanation for the above mentioned field dependence of the critical temperature.

Created on 19-10-2019 by Meidan, Dganit (dganit)
Updaded on 15-01-2020 by Meidan, Dganit (dganit)