Inelastic transport detection of spin quantum tunneling and spin relaxation in single-molecule magnets in the absence of a magnetic field

Abstract

In a scanning tunneling microscope configuration (STM), we study theoretically the effects of quantum tunneling of magnetization (QTM) as well as transport-induced spin relaxation on the electron transport through a single-molecule magnet deposited on a metallic surface. It is shown that for the STM with a high spin-polarized tip, the inelastic current is completely determined by the QTM channel at low temperatures and by the spin relaxation channel at higher temperatures, from which the tunnel splitting and spin-relaxation rate can be directly determined in despite of the absence of a magnetic field. The two types of different mechanisms can be distinguished from each other by current and/or noise spectra.

Electrically tunable Dirac-point resonance induced by a nanomagnet absorbed on the topological insulator surface

“…In this paper, we extend the classic spin model by considering quantum scattering processes involving transitions between its internal magnetic levels, and investigate the spin-inelastic scattering of Dirac electrons off a high-spin nanomagnet with magnetic anisotropy [25][26][27], adsorbed on a TI surface. It is found that introduction of the nanomagnet creates significant low-energy resonance peaks of LDOS, either located exactly at or near the Dirac point, depending on the strength of magnetic anisotropy.…”

Effects of Transverse Magnetic Anisotropy on Current-Induced Spin Switching

“…If the latter component is sufficiently large, it may lead to additional quantum effects, like oscillations due to the geometric Berry phase [15] or quantum tunneling of magnetization (QTM) [16,17]. Although the role of QTM in electronic transport has been studied extensively for normal electrodes [18][19][20], much less is known how it affects the spin-polarized transport [21]. Since QTM allows for the underbarrier transitions between the states on the opposite sides of the energy barrier, it may serve as an additional dephasing mechanism, and thus impede the control of spin state by spin-polarized currents.…”

Negative differential conductance and super-Poissonian shot noise in single-molecule magnet junctions

“…Although the shot noise of electron transport through a SMM has not yet been observed experimentally, new techniques based on carbon nanotubes have been proposed for its possible realization [27]. Recently, the current noise properties of electron transport through a SMM have been attracting much theoretical research interests [28][29][30][31][32][33][34][35] due to they can provide a deeper insight into the nature of transport mechanisms that cannot be obtained by measuring the differential conductance or average current [36,37].…”

“…For example, the super-Poissonian shot noise can be used to reveal the information about the internal level structure of the SMM, the left-right asymmetry of the SMM-electrode coupling [31,32], and the angle between the applied magnetic field and the SMM's easy axis [33]; and distinguish the two types of different nonequilibrium dynamics mechanisms, namely, the quantum tunneling of magnetization process and the thermally excited spin relaxation [34]. In particular, the frequency-resolved shot noise spectrum of artificial SMM, e.g., a CdTe quantum dot doped with a single S = 5/2 Mn spin, can allow one to separately extract the hole and Mn spin relaxation times via the Dicke effect [35].…”

“…Recently, the current noise properties of electron transport through a SMM have been attracting much theoretical research interests 29 30 31 32 33 34 35 36 due to they can provide a deeper insight into the nature of transport mechanisms that cannot be obtained by measuring the differential conductance or average current 37 38 . For example, the super-Poissonian shot noise can be used to reveal the information about the internal level structure of the SMM, the left-right asymmetry of the SMM-electrode coupling 32 33 , and the angle between the applied magnetic field and the SMM's easy axis 34 ; and distinguish the two types of different nonequilibrium dynamics mechanisms, namely, the quantum tunneling of magnetization process and the thermally excited spin relaxation 35 . In particular, the frequency-resolved shot noise spectrum of artificial SMM, e.g., a CdTe quantum dot doped with a single S = 5/2 Mn spin, can allow one to separately extract the hole and Mn spin relaxation times via the Dicke effect 36 .…”