Effect of Biquadratic Exchange Upon Ferromagnetic Two-Magnon Bound States. II. Anisotropic Exchange

1974 ◽  
Vol 52 (1) ◽  
pp. 33-39 ◽  
Author(s):  
D. A. Pink ◽  
R. Ballard
Keyword(s):  
Bound States ◽  
Exchange Interactions ◽  
Bound State ◽  
Exchange Term ◽  
Zero Temperature ◽  
Biquadratic Exchange ◽  
Anisotropic Exchange ◽  
Bound State Spectrum ◽  
Mode Pair ◽  
Isotropic Exchange

We have investigated the two-magnon bound state spectrum of a ferromagnetically ordered system for which the Hamiltonian contains an anisotropic bilinear exchange term, an anisotropic biquadratic exchange term, and a single-ion anisotropy term. The bound states, labelled by a wave vector q which we have taken to be in the [111] direction, were calculated by using zero-temperature Green functions. The principal results are: (i) the existence of single-ion bound states in the absence of single-ion anisotropy and conversely, their absence in the presence of such anisotropy, in contrast to the case in which the exchange interactions are isotropic; (ii) the appearance of an S mode for values of q, [Formula: see text]; (iii) the ordering of bound states for isotropic exchange interactions wherein the S0 mode lies below the S1-mode, D-mode pair and where the S1 mode lies below (above) the D mode if they lie below (above) the band, no longer holds.

Effect of Biquadratic Exchange upon Ferromagnetic Two-Magnon Bound States

1972 ◽  
Vol 50 (15) ◽  
pp. 1728-1735 ◽  
Author(s):  
D. A. Pink ◽  
P. Tremblay
Keyword(s):  
Wave Vector ◽  
Bound States ◽  
Bound State ◽  
Heisenberg Ferromagnet ◽  
Zero Temperature ◽  
Coupling Constant ◽  
Biquadratic Exchange ◽  
Bound State Spectrum ◽  
Magnon Spectrum ◽  
The One

We have calculated the effects of an isotropic biquadratic exchange term having a coupling constant of moderate size [Formula: see text] upon the two-magnon bound state spectrum of an otherwise Heisenberg ferromagnet, with or without single-ion anisotropy, at zero temperature. The bound states are labelled by a wave vector q which we have taken to be in the [111] direction. The two principal results found are: (i) The large effect that K/J has in localizing the '"exchange coupled" bound state, S1 for all values of q above the two-magnon band, when it is sufficiently negative and the spin or pseudo-spin magnitude is of sufficient size. (ii) The change in the value of the wave vector, as K/J changes, at which the one-magnon spectrum crosses that of the "single-ion" bound state, S0.

scholarly journals Comment on: “Some quantum aspects of a particle with electric quadrupole moment interacting with an electric field subject to confining potentials”

2020 ◽  
Vol 35 (25) ◽  
pp. 2075002
Author(s):  
Francisco M. Fernández
Keyword(s):  
Electric Field ◽  
Quadrupole Moment ◽  
Bound States ◽  
Electric Quadrupole ◽  
Bound State ◽  
Electric Quadrupole Moment ◽  
Bound State Spectrum ◽  
Moving Particle ◽  
Quantum Aspects

We analyze the results obtained from a model consisting of the interaction between the electric quadrupole moment of a moving particle and an electric field. We argue that the system does not support bound states because the motion along the [Formula: see text] axis is unbounded. It is shown that the author obtains a wrong bound-state spectrum for the motion in the [Formula: see text] plane and that the existence of allowed cyclotron frequencies is an artifact of the approach.

scholarly journals Fundamental dissipation due to bound fermions in the zero-temperature limit

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Autti ◽  
S. L. Ahlstrom ◽  
R. P. Haley ◽  
A. Jennings ◽  
G. R. Pickett ◽  
...  
Keyword(s):  
Critical Velocity ◽  
Ground State ◽  
Bound States ◽  
Bound State ◽  
Temperature Limit ◽  
Pair Breaking ◽  
Zero Temperature ◽  
Andreev Bound States ◽  
Macroscopic Object

Abstract The ground state of a fermionic condensate is well protected against perturbations in the presence of an isotropic gap. Regions of gap suppression, surfaces and vortex cores which host Andreev-bound states, seemingly lift that strict protection. Here we show that in superfluid 3He the role of bound states is more subtle: when a macroscopic object moves in the superfluid at velocities exceeding the Landau critical velocity, little to no bulk pair breaking takes place, while the damping observed originates from the bound states covering the moving object. We identify two separate timescales that govern the bound state dynamics, one of them much longer than theoretically anticipated, and show that the bound states do not interact with bulk excitations.

scholarly journals The SUSY Yang–Mills plasma in a T-matrix approach

2015 ◽  
Vol 30 (24) ◽  
pp. 1550145 ◽  
Author(s):  
Gwendolyn Lacroix ◽  
Claude Semay ◽  
Fabien Buisseret
Keyword(s):  
Gauge Group ◽  
Bound States ◽  
Bound State ◽  
Lattice Data ◽  
Superstring Theory ◽  
Matrix Formulation ◽  
Yang Mills ◽  
Bound State Spectrum ◽  
T Matrix ◽  
Arbitrary Gauge

In this paper, the thermodynamic properties of [Formula: see text] supersymmetric Yang–Mills theory with an arbitrary gauge group are investigated. In the confined range, we show that identifying the bound state spectrum with a Hagedorn one coming from noncritical closed superstring theory leads to a prediction for the value of the deconfining temperature [Formula: see text] that agrees with recent lattice data. The deconfined phase is studied by resorting to a [Formula: see text]-matrix formulation of statistical mechanics in which the medium under study is seen as a gas of quasigluons and quasigluinos interacting nonperturbatively. Emphasis is put on the temperature range (1–5) [Formula: see text], where the interactions are expected to be strong enough to generate bound states. Binary bound states of gluons and gluinos are indeed found to be bound up to 1.4 [Formula: see text] for any gauge group. The equation of state is then computed numerically for [Formula: see text] and [Formula: see text], and discussed in the case of an arbitrary gauge group. It is found to be nearly independent of the gauge group and very close to that of nonsupersymmetric Yang–Mills when normalized to the Stefan–Boltzmann pressure and expressed as a function of [Formula: see text].

scholarly journals BOUND STATES FROM REGGE TRAJECTORIES IN A SCALAR MODEL

2001 ◽  
Vol 16 (27) ◽  
pp. 4377-4400
Author(s):  
A. WEBER ◽  
J. C. LÓPEZ VIEYRA ◽  
C. R. STEPHENS ◽  
S. DILCHER ◽  
P. O. HESS
Keyword(s):  
Renormalization Group ◽  
Bound States ◽  
Bound State ◽  
Nonrelativistic Limit ◽  
Ladder Approximation ◽  
Scalar Model ◽  
Scalar Theory ◽  
Regge Trajectories ◽  
Bound State Spectrum ◽  
Compare And Contrast

The calculation of bound state properties using renormalization group techniques to compute the corresponding Regge trajectories is presented. In particular, we investigate the bound states in different charge sectors of a scalar theory with interaction ϕ†ϕχ. The resulting bound state spectrum is surprisingly rich. Where possible we compare and contrast with known results of the Bethe–Salpeter equation in the ladder approximation and, in the nonrelativistic limit, with the corresponding Schrödinger equation.

Observation of Excitonic n-Strings In A Quasi-one-Deviensional Charge-Transfer Crystal

1993 ◽  
Vol 328 ◽  
Author(s):  
N. Peyghambarian ◽  
K. Meissner ◽  
B. Fluegel ◽  
S. Mazumdar ◽  
F. Guo ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Bound States ◽  
Theoretical Calculations ◽  
Exchange Interactions ◽  
Bound State ◽  
Collective Excitations ◽  
One Dimension ◽  
Coulomb Interactions ◽  
Light Pulses ◽  
New Type

ABSTRACTCollective excitations, such as plasmons, rotons, electron-hole liquid, and excitonic Molecules, have been extensively studied in condensed Matter.1 Wannier excitons in inorganic semiconductors are bound by the exchange interactions between two electrons of the exciton, and the bound state of More than two excitons is not possible. We demonstrate here a new type of collective excitations,2 bound states of Multiple charge-transfer (CT) excitons. Coulomb interactions in one dimension are shown to bind a train of several (More than two) CT excitons. Experimental evidence for these new type of elementary excitations is reported in a quasi-one-dimensional CT crystal of anthracene PMDA. High density excitation by femtosecond light pulses generates Multi-exciton chains, which we refer to as excitonic n-strings with n = 1, 2, 3, etc., along the stack axis of the crystal. Both the n = 2 excitonic string (biexciton) and the n = 3 string (tri-exciton) are observed. This report provides evidence for an n > 2 exciton chain in this system.2 The stability of the n-string exciton is supported by our theoretical calculations based on the extended Hubbard Hamiltonian in one dimension.

scholarly journals STRONG COULOMB COUPLING IN THE TODOROV EQUATION

1996 ◽  
Vol 11 (30) ◽  
pp. 5303-5325 ◽  
Author(s):  
M. BAWIN ◽  
J. CUGNON ◽  
H. SAZDJIAN
Keyword(s):  
Bound States ◽  
Narrow Band ◽  
Relativistic Quantum ◽  
Goldstone Boson ◽  
Bound State ◽  
Coupling Constant ◽  
Coulomb Coupling ◽  
Strong Coulomb ◽  
Bound State Spectrum ◽  
Adjoint Extension

A positronium-like system with strong Coulomb coupling, considered in its pseudoscalar sector, is studied in the framework of relativistic quantum constraint dynamics with the Todorov choice for the potential. Case’s method of self-adjoint extension of singular potentials, which avoids explicit introduction of regularization cut-offs, is adopted. It is found that, as the coupling constant α increases, the bound state spectrum undergoes an abrupt change at the critical value α=αc=1/2. For α>αc, the mass spectrum displays, in addition to the existing states for α<αc, a new set of an infinite number of bound states concentrated in a narrow band starting at mass W=0; all the states have indefinitely oscillating wave functions near the origin. In the limit α→αc from above, the oscillations disappear and the narrow band of low-lying states shrinks to a single massless state with a mass gap with the rest of the spectrum. This state has the required properties to represent a Goldstone boson and to signal spontaneous breakdown of chiral symmetry.

scholarly journals Finite temperature effects on Majorana bound states in chiral $p$-wave superconductors

2019 ◽  
Vol 6 (5) ◽  
Author(s):  
Henrik Røising ◽  
Roni Ilan ◽  
Tobias Meng ◽  
Steve Simon ◽  
Felix Flicker
Keyword(s):  
Bound States ◽  
Energy Difference ◽  
Bound State ◽  
P Wave ◽  
Zero Temperature ◽  
Free Energy Difference ◽  
Topological Quantum ◽  
Increasing Temperature ◽  
Topological Quantum Computation ◽  
Readout Scheme

We study Majorana modes bound to vortex cores in a chiral \bm{p}𝐩-wave superconductor at temperatures non-negligible compared to the superconducting gap. Thermal occupation of Caroli de Gennes-Matricon (CdGM) states, below the full gap, causes the free energy difference between the two fermionic parity sectors to decay algebraically with increasing temperature. The power law acquires an additional factor of \bm{T^{-1}}𝐓−1 for each bound state thermally excited. The zero-temperature result is exponentially recovered well below the minigap (lowest-lying CdGM level). Our results suggest that temperatures larger than the minigap may not be disastrous for topological quantum computation. We discuss the prospect of precision measurements of pinning forces on vortices as a readout scheme for Majorana qubits.

scholarly journals Isotropic Nature of the Metallic Kagome Ferromagnet Fe3Sn2 at High Temperatures

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 307
Author(s):  
Rebecca L. Dally ◽  
Daniel Phelan ◽  
Nicholas Bishop ◽  
Nirmal J. Ghimire ◽  
Jeffrey W. Lynn
Keyword(s):  
Elevated Temperatures ◽  
Magnetocrystalline Anisotropy ◽  
Inelastic Neutron Scattering ◽  
Exchange Interactions ◽  
Inelastic Neutron ◽  
Temperature Threshold ◽  
Magnetic Exchange ◽  
Spatial Anisotropy ◽  
Isotropic Exchange ◽  
State Spin

Anisotropy and competing exchange interactions have emerged as two central ingredients needed for centrosymmetric materials to exhibit topological spin textures. Fe3Sn2 is thought to have these ingredients as well, as it has recently been discovered to host room temperature skyrmionic bubbles with an accompanying topological Hall effect. We present small-angle inelastic neutron scattering measurements that unambiguously show that Fe3Sn2 is an isotropic ferromagnet below TC≈660 K to at least 480 K—the lower temperature threshold of our experimental configuration. Fe3Sn2 is known to have competing magnetic exchange interactions, correlated electron behavior, weak magnetocrystalline anisotropy, and lattice (spatial) anisotropy; all of these features are thought to play a role in stabilizing skyrmions in centrosymmetric systems. Our results reveal that at the elevated temperatures measured, there is an absence of significant magnetocrystalline anisotropy and that the system behaves as a nearly ideal isotropic exchange interaction ferromagnet, with a spin stiffness D(T=480 K)=168 meV Å2, which extrapolates to a ground state spin stiffness D(T=0 K)=231 meV Å2.

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