65 research outputs found

### Spin liquid phase of the $S=\frac{1}{2}$ $J_1-J_2$ Heisenberg model on the triangular lattice

We study the $S=1/2$ Heisenberg model on the triangular lattice with nearest
neighbor interaction $J_1$ and next nearest neighbor interaction $J_2$ with the
density matrix renormalization group. We are able to study long open cylinders
with widths up to 9 lattice spacings. At an intermediate $J_2$ region $0.06
\lesssim J_2/J_1 \lesssim 0.17$, we find evidence for a spin liquid (SL) state
with short range spin-spin, bond-bond and chiral correlation lengths, bordered
by a classical $120^\circ$ N\'eel ordered state at small $J_2$ and by a two
sub-lattice collinear magnetically ordered state at larger $J_2$. Focusing on
$J_2/J_1 = 0.1$, we find a number of signatures of a gapped SL phase: two
quasi-degenerate ground states on even cylinders, with an energy gap that
decreases exponentially with the cylinder width; a dimerization effect on odd
cylinders; and large spin triplet and singlet bulk gaps.Comment: 5+4 pages, 4+7 figures, 1 table. v2 minor changes made for
publication on PRB rapid communicatio

### Weak plaquette valence bond order in the $S=1/2$ honeycomb $J_1-J_2$ Heisenberg model

Using the density matrix renormalization group, we investigate the $S=1/2$
Heisenberg model on the honeycomb lattice with first- ($J_1$) and
second-neighbor ($J_2$) interactions. We are able to study long open cylinders
with widths up to 12 lattice spacings. For $J_2/J_1$ near 0.3, we find an
apparently paramagnetic phase, bordered by an antiferromagnetic phase for
$J_2\lesssim 0.26$ and by a valence bond crystal for $J_2\gtrsim 0.36$. The
longest correlation length that we find in this intermediate phase is for
plaquette valence bond (PVB) order. This correlation length grows strongly with
cylinder circumference, indicating either quantum criticality or weak PVB
order.Comment: 9 pages, 15 figures, minor changes are made for publication in Phys.
Rev. Let

### Unexpected z-Direction Ising Antiferromagnetic Order in a frustrated Spin-1/2 $J_1-J_2$ XY Model on the Honeycomb Lattice

Using the density matrix renormalization group (DMRG) on wide cylinders, we
study the phase diagram of the spin-1/2 XY model on the honeycomb lattice, with
first-neighbor ($J_1 = 1$) and frustrating second-neighbor ($J_2>0$)
interactions. For the intermediate frustration regime $0.22\lesssim
J_2\lesssim0.36$, we find a surprising antiferromagnetic Ising phase, with
ordered moments pointing along the z axis, despite the absence of any S_z_z
interactions in the Hamiltonian. Surrounding this phase as a function of $J_2$
are antiferromagnetic phases with the moments pointing in the $x-y$ plane for
small $J_2$ and a close competition between an $x-y$ plane magnetic collinear
phase and a dimer phase for large values of $J_2$. We do not find any spin
liquid phases in this model.Comment: 5 pages, 5 figures, minor changes made for publication on PR

### Time reversal Aharonov-Casher effect in mesoscopic rings with Rashba spin-orbital interaction

The time reversal Aharonov-Casher (AC) interference effect in the mesoscopic
ring structures, based on the experiment in Phys. Rev. Lett. \textbf{97},
196803 (2006), is studied theoretically. The transmission curves are calculated
from the scattering matrix formalism, and the time reversal AC interference
frequency is singled out from the Fourier spectra in numerical simulations.
This frequency is in good agreement with analytical result. It is also shown
that in the absent of magnetic field, the Altshuler-Aronov-Spivak type (time
reversal) AC interference retains under the influence of strong disorder, while
the Aharonov-Bohm type AC interference is suppressed.Comment: 5 pages, 4 figures, accepted by Phys. Rev.

### Disorder-Induced Mimicry of a Spin Liquid in YbMgGaO$_4$

We suggest that a randomization of the pseudo-dipolar interaction in the
spin-orbit-generated low-energy Hamiltonian of YbMgGaO$_4$ due to an
inhomogeneous charge environment from a natural mixing of Mg$^{2+}$ and
Ga$^{3+}$ can give rise to orientational spin disorder and mimic a
spin-liquid-like state. In the absence of such quenched disorder, $1/S$ and
density matrix renormalization group calculations both show robust ordered
states for the physically relevant phases of the model. Our scenario is
consistent with the available experimental data and further experiments are
proposed to support it.Comment: 5+ main text, 7+ supplemental, text asymptotically close to PR

### Topography of Spin Liquids on a Triangular Lattice

Spin systems with frustrated anisotropic interactions are of significant
interest due to possible exotic ground states. We have explored their phase
diagram on a nearest-neighbor triangular lattice using the density-matrix
renormalization group and mapped out the topography of the region that can
harbor a spin liquid. We find that this spin-liquid phase is continuously
connected to a previously discovered spin-liquid phase of the isotropic
$J_1\!-\!J_2$ model. The two limits show nearly identical spin correlations,
making the case that their respective spin liquids are isomorphic to each
other.Comment: Accepted to PRL; 5 p., 11+ p. supplemental; main text is longer than
the accepted versio

- …