Related papers: Generic Long-Range Order-Parameter Correlations in…
The ordering temperature of a quasi-one-dimensional system, consisting of weakly interacting quantum spin-1/2 chains with antiferromagnetic spin-frustrating couplings (or zig-zag ladder) is calculated. The results show that a quantum…
It is shown that the quantum phase transition in metallic non-s-wave ferromagnets, or spin nematics, is generically of first order. This is due to a coupling of the order parameter to soft electronic modes that play a role analogous to that…
We investigate the frustrated magnetic interactions in cubic transition metal oxides with orbital degeneracy. The $e_g$ orbitals order easier and their ordering explains the $A$-type antiferromagnetic phase in KCuF$_3$ and LaMnO$_3$. In…
We quantitatively discuss the influence of quenched disorder on the ferromagnetic quantum phase transition in metals, using a theory that describes the coupling of the magnetization to gapless fermionic excitations. In clean systems, the…
Quantum phase transitions have captured the interest of a large community in condensed-matter and atom physics research. The common feature of these very different material classes lies in the fact that the competition between low-energy…
Raman scattering studies of the frustrated spin chain system LiCu$_{2}$O$_{2}$ are reported. Two transitions into a magnetically ordered phase (taken place at temperatures $\sim$ 9 K and $\sim$ 24 K) have been confirmed from the analysis of…
We study the spatial dependence of the order parameter near surfaces belonging to the universality class of the ordinary transition. Special attention is paid to the influence of a small surface magnetic field h_1 at and above the bulk…
This review gives an overview of the quantum phase transition (QPT) problem in metallic ferromagnets, discussing both experimental and theoretical aspects. These QPTs can be classified with respect to the presence and strength of quenched…
In matter, any spontaneous symmetry breaking induces a phase transition characterized by an order parameter, such as the magnetization vector in ferromagnets, or a macroscopic many-electron wave-function in superconductors. Phase…
In low-dimensional magnets, thermal agitation and spatial disorders generate strong spin fluctuations that suppress the long-range magnetic ordering. We develop an analytical equation for the equilibrium magnetization of two-dimensional…
We consider clean Dirac metals where the linear band crossing is caused by a strong spin-orbit interaction, and study the quantum phase transitions from the paramagnetic phase to various magnetic phases, including homogeneous ferromagnets,…
We investigate the spin-spin correlation functions of Ising magnets at complex values of the temperature, T. For one-dimensional chain and ladder systems, we show the existence of a kind of helimagnetic order in the vicinity of contours…
The chiral helimagnet Cr1/3NbS2 has been investigated by magnetic, transport and thermal properties measurements on single crystals and by first principles electronic structure calculations. From the measured field and temperature…
Phase transitions occur when a macroscopic number of local degrees of freedom coherently change their behavior. In ground states of quantum many-body systems, phase transitions due to quantum fluctuations are observed as non-analytic…
Our experimental (neutron diffraction, M\"ossbauer spectroscopy, magnetic susceptibility, specific heat) and numerical studies on the evolution of short- and long-range magnetic order in $\gamma_{\rm II}$-Li\(_2\)FeSiO\(_4\) suggest a…
We describe an ab initio theory of finite temperature magnetism in strongly-correlated electron systems. The formalism is based on spin density functional theory, with a self-interaction corrected local spin density approximation…
The ordered phase of the FeNi system is known to have promising magnetic properties as a rare-earth-free permanent magnet. Understanding the parameter space that controls the order-disorder transformation is important to find growth…
We review the phenomenology of coupled magnetic and electric order parameters for systems in which ferroelectric and incommensurate magnetic order occur simultaneously. We discuss the role that such materials might play in fabricating novel…
The orientation of the order parameter of quantum magnets can be used to store information in a dense and efficient way. Switching this order parameter corresponds to writing data. To understand how this can be done, we study a precessional…
We analyze the symmetry and the nodal structure of the superconducting order parameter in a cubic ferromagnet, such as ZrZn$_2$. We demonstrate how the order parameter symmetry evolves when the electromagnetic interaction of the conduction…