arXiv subjects

Imam Makhfudz

Publications and source records attributed to Imam Makhfudz.

21 records · Page 2Linked to original sources

arXiv2013

Fluctuation-induced First Order Quantum Phase Transition of U(1) Quantum Spin Liquid in Pyrochlore Quantum Antiferromagnet

We show using quantum free energy calculation that the quantum phase transition between U(1) quantum spin liquid (QSL) and antiferromagnet (AFM) phases in pyrochlore quantum antiferromagnet (QAFM) is a first order rather than second order. This change in order from second to first order is induced by gauge fluctuations, which are explicitly taken into account at gauge theory level in our effective low energy theory. We therefore have discovered a fluctuation-induced first order quantum phase transition in pyrochlore QAFM. We explicitly derive the quantum free energy description of this QSL to AFM phase transition and show that it is a weakly first order phase transition. We also briefly discuss the experimental relevance of this result.

cond-mat.str-el↗

arXiv2012

Pnictide Half-Dirac Nodal Quasiparticle Scaling Properties in Vortex State

In this work we investigate the scaling properties of quasiparticles of Pnictide with "half-Dirac" node under magnetic field in vortex state. By computing the density of states, we aim to find in vortex state the form of non-Simon-Lee scaling predicted for such system by several recent works in non-vortex state. We find by exact diagonalization of the Bogoliubov-de Genne Hamiltonian and finite size scaling a $N(E)\sim \sqrt{E}$ power law in the case without magnetic field which agrees with analytical prediction. We consider the vortex state by first studying the hypothetical situation of uniform magnetic field without vortices and then we properly treat the magnetic field-induced vortex lattice by expressing the BdG Hamiltonian in terms of superfluid velocity and Berry's gauge fields. The two calculations are shown to agree with each other. We then analyze quantitatively, the effects of anisotropic dispersion to the scaling properties of vortex lattice and show that the vortex lattice spacings will scale as $d'_y\sim s^{-η}d'_x $ where $1/2\leq η\leq1$ and $s\sim H^2/3$ as compared to $η=1/2$ from dimensional scaling analysis of non-vortex state. A very crucial prediction is also made on an upper bound to the value of 'anomalous dimension' $δ$ of density of states scaling with magnetic field which we find to be $δ\leq1/2$, a quantity that could not be determined conclusively by previous purely analytical works and a quantity that can be measured experimentally.

cond-mat.supr-con↗

arXiv2012

Inertia and chiral edge modes of a skyrmion magnetic bubble

The dynamics of a vortex in a thin-film ferromagnet resembles the motion of a charged massless particle in a uniform magnetic field. Similar dynamics is expected for other magnetic textures with a nonzero skyrmion number. However, recent numerical simulations revealed that skyrmion magnetic bubbles show significant deviations from this model. We show that a skyrmion bubble possesses inertia and derive its mass from the standard theory of a thin-film ferromagnet. Besides center-of-mass motion, other low energy modes are waves on the edge of the bubble traveling with different speeds in opposite directions.

cond-mat.mes-hall↗