相关论文: Crossover from $O(3)$ to $O(4)$ behavior in weakly…
We present a model compound with a spin-1/2 spatially anisotropic frustrated square lattice, in which three antiferromagnetic interactions and one ferromagnetic interaction are competing. We observe an unconventional gradual increase in the…
By means of nuclear spin-lattice relaxation rate 1/T1, we follow the spin dynamics as a function of the applied magnetic field in two gapped one-dimensional quantum antiferromagnets: the anisotropic spin-chain system NiCl2-4SC(NH2)2 and the…
We present a study of the critical phenomena around the quantum critical point in heavy-fermion systems. In the framework of the S=1/2 Kondo lattice model, we introduce an extended decoupling scheme of the Kondo interaction which allows one…
We study the critical behavior of frustrated spin models with noncollinear order in two dimensions, including antiferromagnets on a triangular lattice and fully frustrated antiferromagnets. For this purpose we consider the corresponding…
We study the effects of weak long-ranged antiferromagnetic interactions of strength $Q$ on a spin model with predominant short-ranged ferromagnetic interactions. In three dimensions, this model exhibits an avoided critical point in the…
Critical behavior of three-dimensional classical frustrated antiferromagnets with a collinear spin ordering and with an additional twofold degeneracy of the ground state is studied. We consider two lattice models, whose continuous limit…
The critical behaviour of anisotropic Heisenberg models with two kinds of antiferromagnetically exchange-coupled centers are studied numerically by using finite-size calculations and conformal invariance. These models exhibit the…
We present the full analysis of the normal state of the spin-fermion model near the antiferromagnetic instability in two dimensions. This model describes low-energy fermions interacting with their own collective spin fluctuations, which…
We investigate the phase diagram and, in particular, the nature of the the multicritical point in three-dimensional frustrated $N$-component spin models with noncollinear order in the presence of an external field, for instance easy-axis…
We use the $1/M$ expansion for the $CP^{M-1}$ model to study the long-distance behaviour of the staggered spin susceptibility in the commensurate, two-dimensional quantum antiferromagnet at finite temperature. At $M=\infty$ this model…
We study the phase diagram and multicritical behavior of anisotropic Heisenberg antiferromagnets on a square lattice in the presence of a magnetic field along the easy axis. We argue that, beside the Ising and XY critical lines, the phase…
This work is dedicated to the study of a supersymmetric quantum spherical spin system with short-range interactions. We examine the critical properties both a zero and finite temperature. The model undergoes a quantum phase transition at…
Motivated by the proposal of topological quantum paramagnet in the diamond lattice antiferromagnet NiRh$_2$O$_4$, we propose a minimal model to describe the magnetic interaction and properties of the diamond material with the spin-one local…
We report thermodynamic, neutron diffraction, and inelastic neutron scattering measurements on Cs$_2$RuO$_4$, a member of the celebrated family of frustrated magnets Cs$_2$MX$_4$ (M = Cu, Co, X = Br, Cl). Unlike the previously studied…
We study the dynamics of critical spin fluctuations and hot electrons at the metallic antiferromagnetic quantum critical points with $Z_2$ and $O(2)$ spin symmetries, building upon earlier works on the $O(3)$ symmetric theory. The…
We explore the ferromagnetic quantum critical point in a three-dimensional semimetallic system with upward- and downward-dispersing bands touching at the Fermi level. Evaluating the static spin susceptibility to leading order in the…
Kinetic properties of a two dimensional model of fermions interacting with antiferromagnetic spin excitations near the quantum critical point (QCP) are considered. The temperature or doping are assumed to be sufficiently high, such that the…
The competition between different forms of order is central to the problem of strong correlation. This is particularly true of frustrated systems, which frequently exist at or near to a zero-temperature critical point. Here we show that a…
Dimensionality and symmetry play deterministic roles in the laws of Nature. They are important tools to characterize and understand quantum phase transitions, especially in the limit of strong correlations between spin, orbit, charge, and…
The dimensional crossover in a spin-$S$ nearest neighbor Heisenberg antiferromagnet is discussed as it is tuned from a two-dimensional square lattice, of lattice spacing $a$, towards a spin chain by varying the width $L_y$ of a…