1,354,258 research outputs found
Hubbard model on triangular N -leg cylinders: Chiral and nonchiral spin liquids
No full textThe existence of a gapped chiral spin liquid has been recently suggested in the vicinity of the metal-insulator transition of the Hubbard model on the triangular lattice, by intensive density-matrix renormalization group (DMRG) simulations [A. Szasz, J. Motruk, M. P. Zaletel, and J. E. Moore, Phys. Rev. X 10, 021042 (2020)10.1103/PhysRevX.10.021042]. Here, we report the results obtained within the variational Monte Carlo technique based upon Jastrow-Slater wave functions, implemented with backflow correlations. As in DMRG calculations, we consider N-leg cylinders. For N=4 and in the presence of a next-nearest-neighbor hopping, a chiral spin liquid emerges between the metal and the insulator with magnetic quasi-long-range order. Within our approach, the chiral state is gapped and breaks the reflection symmetry. By contrast, for both N=5 and 6, the chiral spin liquid is not the state with the lowest variational energy: in the former case, a nematic spin liquid is found in the entire insulating regime, while for the less frustrated case with N=6 the results are very similar to that obtained on two-dimensional clusters [L. F. Tocchio, A. Montorsi, and F. Becca, Phys. Rev. B 102, 115150 (2020)2469-995010.1103/PhysRevB.102.115150], with an antiferromagnetic phase close to the metal-insulator transition and a nematic spin liquid in the strong-coupling regime
Hubbard model on triangular N-leg cylinders: Chiral and nonchiral spin liquids
No full textThe existence of a gapped chiral spin liquid has been recently suggested in the vicinity of the metal-insulator transition of the Hubbard model on the triangular lattice, by intensive density-matrix renormalization group (DMRG) simulations [A. Szasz, J. Motruk, M. P. Zaletel, and J. E. Moore, Phys. Rev. X 021042 (2020)]. Here, we report the results obtained within the variational Monte Carlo technique based upon Jastrow-Slater wave functions, implemented with backflow correlations. As in DMRG calculations, we consider N-leg cylinders. For N = 4 and in the presence of a next-nearest-neighbor hopping, a chiral spin liquid emerges between the metal and the insulator with magnetic quasi-long-range order. Within our approach, the chiral state is gapped and breaks the reflection symmetry. By contrast, for both N = 5 and 6, the chiral spin liquid is not the state with the lowest variational energy: in the former case, a nematic spin liquid is found in the entire insulating regime, while for the less frustrated case with N = 6 the results are very similar to that obtained on two-dimensional clusters [L. F. Tocchio, A. Montorsi, and F. Becca, Phys. Rev. B 102, 115150 (2020)], with an antiferromagnetic phase close to the metal-insulator transition and a nematic spin liquid in the strong-coupling regime
Stripes in the extended Hubbard model: A Variational Monte Carlo analysis
No full textBy using variational quantum Monte Carlo techniques, we investigate the
instauration of stripes (i.e., charge and spin inhomogeneities) in the Hubbard
model on the square lattice at hole doping , with both nearest-
() and next-nearest-neighbor hopping (). Stripes with different
wavelengths (denoting the periodicity of the charge inhomogeneity)
and character (bond- or site-centered) are stabilized for sufficiently large
values of the electron-electron interaction . The general trend is that
increases going from negative to positive values of and
decreases by increasing . In particular, the stripe obtained
for and [L.F. Tocchio, A. Montorsi, and F. Becca, SciPost
Phys. {\bf 7}, 21 (2019)] shrinks to for . For
, the stripe with is found to be remarkably stable,
while for , stripes with wavelength and
are also obtained. In all these cases, pair-pair correlations are highly
suppressed with respect to the uniform state (obtained for large values of
), suggesting that striped states are not superconducting at
.Comment: 18 pages, 10 figures, submission to SciPos
About declarative semantics of logic-based agent languages
No full textIn this paper we cope with providing an approach to declarative semantics
of logic-based agent-oriented languages, taking then as a case-study the
language DALI which has been previously defined by the authors. This “evolutionary
semantics” does not resort to a concept of state: rather, it models reception
of events as program transformation steps, that produce a “program evolution”
and a corresponding “semantic evolution”. Communication among agents
and multi-agent systems is also taken into account. The aim is that of modeling
agent’s evolution according to either external (environmental) or internal changes
in a logical way, thus allowing in principle the adoption of formal verification
methods. We also intend to create a common ground for relating and comparing
different approaches/languages
Microelectromechanical systems integrating motion and displacement sensors
No full textThe purpose of this chapter is to describe the working principle of the microelectromechanical systems (MEMS) devices used in motion sensors and to consider their level of sophistication, performance limits, and future evolution. The integration of a multiparameter sensor in a single unit can increase the smartness of the device and enables the implementation of new functionalities in existing electronic systems. MEMS accelerometers, gyroscopes, and magnetometers are discussed in detail, as they represent the core devices for the development of a high-precision inertial measurement unit. At the end of the chapter, consideration is given to the evolution of these units integrating new MEMS devices for added functionalities, such as pressure sensing or proximity measurements
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