arXiv subjects

Z. Papić

Publications and source records attributed to Z. Papić.

22 records · Page 2Linked to original sources

arXiv2010

Transition from two-component 332 Halperin state to one-component Jain state at filling factor ν=2/5

We study the transition induced by tunneling from the two-component 332 Halperin's state to the one-component Jain's state at the filling factor ν=2/5. In exact diagonalizations of small systems two possibilities for the transition are found: (a) avoided level crossing, and (b) level crossing i.e. first-order transition in the case of Coulomb interaction and short range interaction, respectively. An effective bosonic model with p-wave pairing for the transition is proposed. The relevance of the Gaffnian state for the transition is discussed as well as possible consequences of our model on the effective description of the Jain state.

cond-mat.mes-hall↗

arXiv2009

Interaction-tuned compressible-to-incompressible phase transitions in the quantum Hall systems

We analyze transitions between quantum Hall ground states at prominent filling factors $ν$ in the spherical geometry by tuning the width parameter of the Zhang-Das Sarma interaction potential. We find that incompressible ground states evolve adiabatically under this tuning, whereas the compressible ones are driven through a first order phase transition. Overlap calculations show that the resulting phase is increasingly well described by appropriate analytic model wavefunctions (Laughlin, Moore-Read, Read-Rezayi). This scenario is shared by both odd ($ν=1/3, 1/5, 3/5, 7/3, 11/5, 13/5$) and even denominator states ($ν=1/2, 1/4, 5/2, 9/4$). In particular, the Fermi liquid-like state at $ν=1/2$ gives way, at large enough value of the width parameter, to an incompressible state identified as the Moore-Read Pfaffian on the basis of its entanglement spectrum.

cond-mat.str-el↗

arXiv2009

Nonperturbative approach to the quantum Hall bilayer

We develop a nonperturbative approach to the quantum Hall bilayer (QHB) at ν=1 using trial wave functions. We predict phases of the QHB for arbitrary distance d and, our approach, in a dual picture, naturally introduces a new kind of quasiparticles - neutral fermions. Neutral fermion is a composite of two merons of the same vorticity and opposite charge. For small d (i.e. in the superfluid phase), neutral fermions appear as dipoles. At larger d dipoles dissociate into the phase of the two decoupled Fermi-liquid-like states. This scenario is relevant for the experimental situation where impurities lock charged merons. In a translation invariant (clean) system, continuous creation and annihilation of meron-antimeron pairs evolves the QHB toward a paired phase. The quantum fluctuations fix the form of the pairing function to g(z)=1/z^*. A part of the description of the paired phase is the 2D superconductor i.e. BF Chern-Simons theory. The paired phase is not very distinct from the superfluid phase.

cond-mat.mes-hall↗

arXiv2009

Theoretical expectations for a fractional quantum Hall effect in graphene

Due to its fourfold spin-valley degeneracy, graphene in a strong magnetic field may be viewed as a four-component quantum Hall system. We investigate the consequences of this particular structure on a possible, yet unobserved, fractional quantum Hall effect in graphene within a trial-wavefunction approach and exact-diagonalisation calculations. This trial-wavefunction approach generalises an original idea by Halperin to account for the SU(2) spin in semiconductor heterostructures with a relatively weak Zeeman effect. Whereas the four-component structure at a filling factor nu=1/3 adds simply a SU(4)-ferromagnetic spinor ordering to the otherwise unaltered Laughlin state, the system favours a valley-unpolarised state at nu=2/5 and a completely unpolarised state at nu=4/9. Due to the similar behaviour of the interaction potential in the zero-energy graphene Landau level and the first excited one, we expect these states to be present in both levels.

cond-mat.mes-hall↗