Magnetotransport study of the canted antiferromagnetic phase in bilayerν=2quantum Hall state

Abstract

Magnetotransport properties are investigated in the bilayer quantum Hall state at the total filling factor ν = 2. We measured the activation energy elaborately as a function of the total electron density and the density difference between the two layers. Our experimental data demonstrate clearly the emergence of the canted antiferromagnetic (CAF) phase between the ferromagnetic phase and the spin-singlet phase. The stability of the CAF phase is discussed by the comparison between experimental results and theoretical calculations using a Hartree-Fock approximation and an exact diagonalization study. The data reveal also an intrinsic structure of the CAF phase divided into two regions according to the dominancy between the intralayer and interlayer correlations.

Observation of an in-plane magnetic-field-driven phase transition in a quantum Hall system with SU(4) symmetry

“…Actually for a bilayer system at = 2 where sometimes four Landau levels are close to degeneracy, the ground state is extensively studied by several groups and a similar pairing state of pseudospins or layers can become energetically favorable. 16 We speculate that similar SU͑2͒ to SU͑4͒ phase transition phenomenon can be observed in bilayer systems at some appropriate regions. Of course, there are possibly different competing orders, such as a stripe state with broken translational and spin symmetries, which is commonly believed to occur at very large in-plane magnetic fields.…”

Transport in two-dimensional modulation-doped semiconductor structures

“…Many important fundamental discoveries [1][2][3][4][5][6][7][8][9][10][11][12][13] have been made in the context of studying 2DEG transport properties such as integer and fractional quantum Hall effects 2 , Mott variable range hoping 3 , weak and strong localization 3,4 , Wigner crystallization 5 , possible anyonic non-Abelian fractional quantum Hall effects 1,6 , stripe and bubble 2D interacting phases 7 , 2D metal-insulatortransitions 4 , microwave-induced-resistance oscillations 8 , Coulomb drag 9 , interlayer spontaneous coherence 10 , interlayer canted antiferromagnetism 11 , bilayer evendenominator fractional quantum Hall effect 12 , monolayer even-denominator fractional quantum Hall effect 13 , and so on. In many situations, new (and often unexpected) experimental discoveries in 2D physics become possible because of the continuous enhancement in the 2DEG mobility µ defined as µ ≡ σ/ne = eτ /m where m and τ are respectively the carrier effective mass and the transport relaxation time, through careful materials improvement and clever sample design.…”

Nambu–Goldstone modes and the Josephson supercurrent in the bilayer quantum Hall system

“…We calculate the isospin components (73) with the use of n i = U ni , and substitute them into the effective Hamiltonian (17). In this way we obtain the effective Hamiltonian for η i , which is…”

“…On the other hand, at ν = 2 the bilayer QH system has three phases, the spin-ferromagnet and pseudospin-singlet phase (abridged as the spin phase), the spin-singlet and pseudospin ferromagnet phase (abridged as the pseudospin phase) and a canted antiferromagnetic phase [14][15][16][17] (abridged as the CAF phase), depending on the relative strength between the Zeeman energy ∆ Z and the interlayer tunneling energy ∆ SAS . The pattern of the symmetry breaking is SU(4)→U(1)⊗SU( 2)⊗SU(2), associated with which there appear four complex NG modes [18].…”