scholarly journals Non-Hermitian indirect exchange interaction in a topological insulator coupled to a ferromagnetic metal

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mir Vahid Hosseini ◽  
Mehdi Askari
Keyword(s):  
Decay Rate ◽  
Topological Insulator ◽  
Magnetic Impurity ◽  
Surface States ◽  
Decay Rates ◽  
Ferromagnetic Metal ◽  
Magnetic Impurities ◽  
Indirect Exchange ◽  
Charge Decay ◽  
Spatial Oscillations

AbstractWe theoretically demonstrate non-Hermitian indirect interaction between two magnetic impurities placed at the interface between a 3D topological insulator and a ferromagnetic metal. The coupling of topological insulator and the ferromagnet introduces not only Zeeman exchange field on the surface states but also broadening to transfer the charge and spin between the surface states of the topological insulator and the metallic states of the ferromagnet. While the former provides bandgap at the charge neutrality point, the latter causes non-Hermiticity. Using the Green’s function method, we calculate the range functions of magnetic impurity interactions. We show that the charge decay rate provides a coupling between evanescent modes near the bandgap and traveling modes near the band edge. However, the spin decay rate induces a stronger coupling than the charge decay rate so that higher energy traveling modes can be coupled to lower energy evanescent ones. This results in a non-monotonic behavior of the range functions in terms of distance and decay rates in the subgap regime. In the over gap regime, depending on the type of decay rate and on the distance, the amplitude of spatial oscillations would be damped or promoted.

Optical resonant RKKY interaction in nanosystems

2015 ◽  
Vol 93 (11) ◽  
pp. 1269-1273
Author(s):  
Peng Feng ◽  
Jianqiao Xie
Keyword(s):  
Exchange Interaction ◽  
Conduction Electron ◽  
Laser Field ◽  
Magnetic Impurity ◽  
Magnetic Impurities ◽  
Rkky Interaction ◽  
Resonant Frequencies ◽  
Spintronic Devices ◽  
Indirect Exchange ◽  
Nonmagnetic Metals

Conduction electron spins interacting with magnetic impurity spins can lead to an indirect exchange interaction between magnetic impurities in nonmagnetic metals or semiconductors, namely, RKKY interaction. In general, this RKKY coupling is too weak to apply on devices. In this paper, we find that when a laser field of appropriate frequency irradiates the nanosystems, it can greatly strengthen the RKKY interaction. This is the so-called optical resonant RKKY interaction. We give the resonant frequencies for different size samples, and calculate the exchange integrals for these samples on the near-resonant conditions. This optical resonant RKKY coupling may be strong enough to guarantee its application on spintronic devices.

Effects of A.C. Stress on Charge and Voltage Decay Rates of PZT Thin Film Capacitors for DRAM Applications

1994 ◽  
Vol 361 ◽  
Author(s):  
Rajesh B. Khamankar ◽  
Jiyoung Kim ◽  
Bo Jiang ◽  
Jack Lee
Keyword(s):  
Thin Film ◽  
Decay Rate ◽  
Decay Rates ◽  
Signal Loss ◽  
Charge Voltage ◽  
Electrical Stress ◽  
Voltage Decay ◽  
Thin Film Capacitors ◽  
Pzt Thin Film ◽  
Charge Decay

ABSTRACTA PZT thin film capacitor displays a reduction in the charge storage density (Qc') after the device has undergone pulsed electrical stress. This changes the charge-voltage relationship for the devices. The effect of this change in the Q-V relationship on the DRAM READ time is described. Measurements of the charge and voltage decay rates have been previously identified as ideal techniques for characterizing signal loss. For the first time the effects of electrical stress on these rates have been studied. While the charge decay rate decreases with an increase in the number of stress cycles for both the bipolar and unipolar stress, the voltage decay rate decreases after unipolar stress but it increases for bipolar stress at lower stress voltages. The implications of these results on the DRAM performance shall be discussed.

Large Damping Enhancement in Dirac‐Semimetal–Ferromagnetic‐Metal Layered Structures Caused by Topological Surface States

2021 ◽  
pp. 2008411
Author(s):  
Jinjun Ding ◽  
Chuanpu Liu ◽  
Yuejie Zhang ◽  
Vijaysankar Kalappattil ◽  
Rui Yu ◽  
...  
Keyword(s):  
Surface States ◽  
Layered Structures ◽  
Ferromagnetic Metal ◽  
Dirac Semimetal ◽  
Topological Surface

scholarly journals Many-impurity scattering on the surface of a topological insulator

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
José Luis Hernando ◽  
Yuriko Baba ◽  
Elena Díaz ◽  
Francisco Domínguez-Adame
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Topological Insulator ◽  
Disordered Systems ◽  
Spectral Properties ◽  
Random Distribution ◽  
Surface States ◽  
Impurity Scattering ◽  
Self Consistent ◽  
The Impact

AbstractWe theoretically address the impact of a random distribution of non-magnetic impurities on the electron states formed at the surface of a topological insulator. The interaction of electrons with the impurities is accounted for by a separable pseudo-potential method that allows us to obtain closed expressions for the density of states. Spectral properties of surface states are assessed by means of the Green’s function averaged over disorder realisations. For comparison purposes, the configurationally averaged Green’s function is calculated by means of two different self-consistent methods, namely the self-consistent Born approximation (SCBA) and the coherent potential approximation (CPA). The latter is often regarded as the best single-site theory for the study of the spectral properties of disordered systems. However, although a large number of works employ the SCBA for the analysis of many-impurity scattering on the surface of a topological insulator, CPA studies of the same problem are scarce in the literature. In this work, we find that the SCBA overestimates the impact of the random distribution of impurities on the spectral properties of surface states compared to the CPA predictions. The difference is more pronounced when increasing the magnitude of the disorder.

scholarly journals The gigantic Rashba effect of surface states energetically buried in the topological insulator Bi2Te2Se

2014 ◽  
Vol 16 (6) ◽  
pp. 065016 ◽  
Author(s):  
K Miyamoto ◽  
T Okuda ◽  
M Nurmamat ◽  
M Nakatake ◽  
H Namatame ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Surface States ◽  
Rashba Effect ◽  
Effect Of Surface

scholarly journals Faraday Rotation Due to Surface States in the Topological Insulator (Bi1–xSbx)2Te3

Nano Letters ◽  
2017 ◽  
Vol 17 (2) ◽  
pp. 980-984 ◽  
Author(s):  
Yinming Shao ◽  
Kirk W. Post ◽  
Jhih-Sheng Wu ◽  
Siyuan Dai ◽  
Alex J. Frenzel ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Faraday Rotation ◽  
Surface States

scholarly journals Induced unconventional superconductivity on the surface states of Bi2Te3 topological insulator

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Sophie Charpentier ◽  
Luca Galletti ◽  
Gunta Kunakova ◽  
Riccardo Arpaia ◽  
Yuxin Song ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Topological Insulator ◽  
Quantum Interference ◽  
Order Parameter ◽  
Thermal Strain ◽  
Surface States ◽  
Field Pattern ◽  
Key Factors ◽  
Ordered Phases ◽  
Simultaneous Existence

Abstract Topological superconductivity is central to a variety of novel phenomena involving the interplay between topologically ordered phases and broken-symmetry states. The key ingredient is an unconventional order parameter, with an orbital component containing a chiral p x  + ip y wave term. Here we present phase-sensitive measurements, based on the quantum interference in nanoscale Josephson junctions, realized by using Bi2Te3 topological insulator. We demonstrate that the induced superconductivity is unconventional and consistent with a sign-changing order parameter, such as a chiral p x  + ip y component. The magnetic field pattern of the junctions shows a dip at zero externally applied magnetic field, which is an incontrovertible signature of the simultaneous existence of 0 and π coupling within the junction, inherent to a non trivial order parameter phase. The nano-textured morphology of the Bi2Te3 flakes, and the dramatic role played by thermal strain are the surprising key factors for the display of an unconventional induced order parameter.

Sign in / Sign up

Export Citation Format

Share Document