scholarly journals Supersymmetric spin–phonon coupling prevents odd integer spins from quantum tunneling

2021 ◽  
Vol 94 (3) ◽  
Author(s):  
Kilian Irländer ◽  
Heinz-Jürgen Schmidt ◽  
Jürgen Schnack
Keyword(s):  
Quantum Tunneling ◽  
Degrees Of Freedom ◽  
Spin Systems ◽  
Phonon Coupling ◽  
Temperature Dependent ◽  
Integer Spin ◽  
Quantum Numbers ◽  
Spin Quantum ◽  
Strong Spin

AbstractQuantum tunneling of the magnetization is a phenomenon that impedes the use of small anisotropic spin systems for storage purposes even at the lowest temperatures. Phonons, usually considered for temperature dependent relaxation of magnetization over the anisotropy barrier, also contribute to magnetization tunneling for integer spin quantum numbers. Here we demonstrate that certain spin–phonon Hamiltonians are unexpectedly robust against the opening of a tunneling gap, even for strong spin–phonon coupling. The key to understanding this phenomenon is provided by an underlying supersymmetry that involves both spin and phonon degrees of freedom.

Weak ferromagnets with integer and half-integer spin quantum numbers

2005 ◽  
Vol 355 (1-4) ◽  
pp. 90-99 ◽  
Author(s):  
U. Köbler ◽  
A. Hoser ◽  
J. Bos ◽  
W. Schäfer ◽  
L. Pohlmann
Keyword(s):  
Integer Spin ◽  
Half Integer ◽  
Quantum Numbers ◽  
Spin Quantum

scholarly journals Quantum Tunneling in Half-Integer Spin Systems

2001 ◽  
Vol 106 (3) ◽  
pp. 533-549 ◽  
Author(s):  
S. Miyashita ◽  
N. Nagaosa
Keyword(s):  
Quantum Tunneling ◽  
Spin Systems ◽  
Integer Spin ◽  
Half Integer

Temperature dependent electron–phonon coupling of Au resolved via lattice dynamics measured with sub-picosecond infrared pulses

2021 ◽  
Vol 129 (19) ◽  
pp. 193104
Author(s):  
John A. Tomko ◽  
Sushant Kumar ◽  
Ravishankar Sundararaman ◽  
Patrick E. Hopkins
Keyword(s):  
Lattice Dynamics ◽  
Phonon Coupling ◽  
Temperature Dependent ◽  
Electron Phonon Coupling

scholarly journals A chiral switchable photovoltaic ferroelectric 1D perovskite

2020 ◽  
Vol 6 (9) ◽  
pp. eaay4213 ◽  
Author(s):  
Yang Hu ◽  
Fred Florio ◽  
Zhizhong Chen ◽  
W. Adam Phelan ◽  
Maxime A. Siegler ◽  
...  
Keyword(s):  
Electric Fields ◽  
Mirror Symmetry ◽  
Degrees Of Freedom ◽  
Electrical Measurements ◽  
Temperature Dependent ◽  
Paraelectric Phase Transition ◽  
Strongly Coupled ◽  
Yield Phenomena ◽  
Hybrid Perovskite ◽  
Low Dimensional

Spin and valley degrees of freedom in materials without inversion symmetry promise previously unknown device functionalities, such as spin-valleytronics. Control of material symmetry with electric fields (ferroelectricity), while breaking additional symmetries, including mirror symmetry, could yield phenomena where chirality, spin, valley, and crystal potential are strongly coupled. Here we report the synthesis of a halide perovskite semiconductor that is simultaneously photoferroelectricity switchable and chiral. Spectroscopic and structural analysis, and first-principles calculations, determine the material to be a previously unknown low-dimensional hybrid perovskite (R)-(−)-1-cyclohexylethylammonium/(S)-(+)-1 cyclohexylethylammonium) PbI3. Optical and electrical measurements characterize its semiconducting, ferroelectric, switchable pyroelectricity and switchable photoferroelectric properties. Temperature dependent structural, dielectric and transport measurements reveal a ferroelectric-paraelectric phase transition. Circular dichroism spectroscopy confirms its chirality. The development of a material with such a combination of these properties will facilitate the exploration of phenomena such as electric field and chiral enantiomer–dependent Rashba-Dresselhaus splitting and circular photogalvanic effects.

scholarly journals Design and Analysis of a 1D Actively Stabilized System with Viscoelastic Damping Support

Actuators ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 33
Author(s):  
Josef Passenbrunner ◽  
Gerald Jungmayr ◽  
Wolfgang Amrhein
Keyword(s):  
Degrees Of Freedom ◽  
Nonlinear Behavior ◽  
Axial Rotation ◽  
Test System ◽  
Axial Position ◽  
Viscoelastic Damping ◽  
Temperature Dependent ◽  
Temperature Dependent Properties ◽  
Rotor Dynamic ◽  
Damping Capability

Passively magnetically stabilized degrees of freedom yield the benefit of reduced complexity and therefore costs. However, the application of passive magnetic bearings (PMBs) also features some drawbacks. The poor damping capability leads to exaggerated deflection amplitudes when passing the resonance speeds of the applied system. This results in the necessity of external damping. Complying with the goal of costs and complexity, viscoelastic materials offer a suitable solution. However, these materials show high frequency and temperature dependent properties which induce the necessity of a proper model. Thus, the design of systems, as presented in this paper, requires accurate modeling of the dynamic behavior including the nonlinear characteristic of damping elements to predict the system displacements. In the investigated setup only two degrees of freedom remain to be controlled actively. These are the axial rotation and the axial position of the rotor which are controlled by the motor and an active magnetic axial bearing (AMB). This article focuses on the rotor dynamic modeling of a radial passively magnetically stabilized system especially considering the nonlinear behavior of viscoelastic damping elements. Finally, the results from the analytic model are verified by measurements on a manufactures test system.

Physics of Spin-Orbit-Coupled Oxides

2021 ◽  
Author(s):  
Gang Cao ◽  
Lance DeLong
Keyword(s):  
Giant Magnetoresistance ◽  
Degrees Of Freedom ◽  
High Temperature Superconductivity ◽  
Transition Element ◽  
Spin Orbit ◽  
Transition Elements ◽  
Crystalline Electric Field ◽  
Magnetic Exchange ◽  
Spin Orbit Interactions ◽  
Strong Spin

Prior to 2010, most research on the physics and chemistry of transition metal oxides was dominated by compounds of the 3d-transition elements such as Cr, Mn, Fe, Co, Ni, and Cu. These materials exhibited novel, important phenomena that include giant magnetoresistance in manganites, as well as high-temperature superconductivity in doped La2CuO4 and related cuprates. The discovery in 1994 of an exotic superconducting state in Sr2RuO4 shifted some interest toward ruthenates. Moreover, the realization in 2008 that a novel variant of the classic Mott metal-insulator transition was at play in Sr2IrO4 provided the impetus for a burgeoning group of studies of the influence of strong spin-orbit interactions in “heavy” (4d- and 5d-) transition-element oxides. This book reviews recent experimental and theoretical evidence that the physical and structural properties of 4d- and 5d-oxides are decisively influenced by strong spin-orbit interactions that compete or collaborate with comparable Coulomb, magnetic exchange, and crystalline electric field interactions. The combined effect leads to unusual ground states and magnetic frustration that are unique to this class of materials. Novel couplings between the orbital/lattice and spin degrees of freedom, which lead to unusual types of magnetic order and other exotic phenomena, challenge current theoretical models. Of particular interest are recent investigations of iridates and ruthenates focusing on strong spin-orbit interactions that couple the lattice and spin degrees of freedom.

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