8 research outputs found
Quantum phases of dimerized and frustrated Heisenberg spin chains with s = 1/2, 1 and 3/2: an entanglement entropy and fidelity study
We study here different regions in phase diagrams of the spin-1/2, spin-1 and
spin-3/2 one dimensional antiferromagnetic Heisenberg systems with frustration
(next-nearest-neighbor interaction ) and dimerization (). In
particular, we analyze the behaviors of the bipartite entanglement entropy and
fidelity at the gapless to gapped phase transitions and across the lines
separating different phases in the plane. All the calculations in
this work are based on numerical exact diagonalizations of finite systems.Comment: 12 pages, 15 figures; provided some finite size analysis results,
some changes in text accordingly; to appear in J. Phys.: Condens. Matte
Exact Entanglement Studies of Strongly Correlated Systems: Role of Long-Range Interactions and Symmetries of the System
We study the bipartite entanglement of strongly correlated systems using
exact diagonalization techniques. In particular, we examine how the
entanglement changes in the presence of long-range interactions by studying the
Pariser-Parr-Pople model with long-range interactions. We compare the results
for this model with those obtained for the Hubbard and Heisenberg models with
short-range interactions. This study helps us to understand why the density
matrix renormalization group (DMRG) technique is so successful even in the
presence of long-range interactions. To better understand the behavior of
long-range interactions and why the DMRG works well with it, we study the
entanglement spectrum of the ground state and a few excited states of finite
chains. We also investigate if the symmetry properties of a state vector have
any significance in relation to its entanglement. Finally, we make an
interesting observation on the entanglement profiles of different states
(across the energy spectrum) in comparison with the the corresponding profile
of the density of states. We use isotropic chains and a molecule with
non-Abelian symmetry for these numerical investigations.Comment: 24 pages, 11 figures and 2 table
Studies on a frustrated Heisenberg spin chain with alternating ferromagnetic and antiferromagnetic exchanges
Above-room-temperature ferromagnetism in ultrathin van der Waals magnet
Two-dimensional (2D) magnetic van der Waals materials provide a powerful
platform for studying fundamental physics of low-dimensional magnetism,
engineering novel magnetic phases, and enabling ultrathin and highly tunable
spintronic devices. To realize high quality and practical devices for such
applications, there is a critical need for robust 2D magnets with ordering
temperatures above room temperature that can be created via exfoliation. Here
the study of exfoliated flakes of cobalt substituted Fe5GeTe2 (CFGT) exhibiting
magnetism above room temperature is reported. Via quantum magnetic imaging with
nitrogen-vacancy centers in diamond, ferromagnetism at room temperature was
observed in CFGT flakes as thin as 16 nm. This corresponds to one of the
thinnest room-temperature 2D magnet flakes exfoliated from robust single
crystals, reaching a thickness relevant to practical spintronic applications.
The Curie temperature Tc of CFGT ranges from 310 K in the thinnest flake
studied to 328 K in the bulk. To investigate the prospect of high-temperature
monolayer ferromagnetism, Monte Carlo calculations were performed which
predicted a high value of Tc ~270 K in CFGT monolayers. Pathways towards
further enhancing monolayer Tc are discussed. These results support CFGT as a
promising platform to realize high-quality room-temperature 2D magnet devices