920 research outputs found
Deconfined Quantum Critical Point on the Triangular Lattice
We first propose a topological term that captures the "intertwinement"
between the standard "" antiferromagnetic order (or
the so-called 120 state) and the "" valence
solid bond (VBS) order for spin-1/2 systems on a triangular lattice. Then using
a controlled renormalization group calculation, we demonstrate that there
exists an unfine-tuned direct continuous deconfined quantum critical point
(dQCP) between the two ordered phases mentioned above. This dQCP is described
by the quantum electrodynamics (QED) with an emergent
PSU(4)=SU(4)/ symmetry only at the critical point. The topological term
aforementioned is also naturally derived from the QED. We also point
out that physics around this dQCP is analogous to the boundary of a
bosonic symmetry protected topological state with on-site symmetries only
Resonant x-ray scattering reveals possible disappearance of magnetic order under hydrostatic pressure in the Kitaev candidate -LiIrO
Honeycomb iridates such as -LiIrO are argued to realize
Kitaev spin-anisotropic magnetic exchange, along with Heisenberg and possibly
other couplings. While systems with pure Kitaev interactions are candidates to
realize a quantum spin liquid ground state, in -LiIrO it has
been shown that the balance of magnetic interactions leads to the
incommensurate spiral spin order at ambient pressure below 38 K. We study the
fragility of this state in single crystals of -LiIrO using
resonant x-ray scattering (RXS) under applied hydrostatic pressures of up to
3.0 GPa. RXS is a direct probe of the underlying electronic order, and we
observe the abrupt disappearance of the =(0.57, 0, 0) spiral order at a
critical pressure GPa with no accompanying change in the symmetry
of the lattice. This dramatic disappearance is in stark contrast with recent
studies of -LiIrO that show continuous suppression of the spiral
order in magnetic field; under pressure, a new and possibly nonmagnetic ground
state emerges
Interplay of interactions and disorder at the superfluid-insulator transition: A dirty two-dimensional quantum critical point
We study the stability of the Wilson-Fisher fixed point of the quantum O(2N) vector model to quenched disorder in the large-N limit. While a random mass is strongly relevant at the Gaussian fixed point, its effect is screened by the strong interactions of the Wilson-Fisher fixed point. This enables a perturbative renormalization group study of the interplay of disorder and interactions about this fixed point. We show that, in contrast to the spiralling flows obtained in earlier double-ε expansions, the theory flows directly to a quantum critical point characterized by finite disorder and interactions. The critical exponents we obtain for this transition are in remarkable agreement with numerical studies of the superfluid-Mott glass transition. We additionally discuss the stability of this fixed point to scalar and vector potential disorder and use proposed boson-fermion dualities to make conjectures regarding the effects of weak disorder on dual Abelian Higgs and Chern-Simons-Dirac fermion theories when N = 1
- …