Berry-Phase Blockade in Single-Molecule Magnets

Abstract

We formulate the problem of electron transport through a single-molecule magnet (SMM) in the Coulomb blockade regime taking into account topological interference effects for the tunneling of the large spin of a SMM. The interference originates from spin Berry phases associated with different tunneling paths. We show that, in the case of incoherent spin states, it is essential to place the SMM between oppositely spin-polarized source and drain leads in order to detect the spin tunneling in the stationary current, which exhibits topological zeros as a function of the transverse magnetic field.

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

“…Therefore, we can directly probe the QTM by the measurement of the inelastic current in this geometry. The present discussion is somewhat similar to that made by González and Leuenberger 16 , who proposed the detection of the QTM in sequential tunneling through an SMM placed between two oppositely spinpolarized leads. In the present work, the probing of the QTM effect can be accessible in the STM system with only one spin-polarized tip, which might relax technological conditions and be more favorable to experimental observations.…”

“…Strong enough anisotropy B 2n is desirable because it can generate a large tunnel splitting ∆ m,−m and a pronounced current signature. In addition, when the tunnel splitting is tuned by an applied magnetic field 16 , we also can observe the Berry-phase blockade since if ∆ m,−m = 0, I in will be completely suppressed due to Γ m,−m ∝ ∆ 2 m,−m . At higher temperatures (T > 3.5K), the current magnitude no longer depends on ∆ m,−m (i.e., the magnetic parameters D and B 2n ), e.g., in Fig.…”

“…(10) reduces to 1 Iin = 1 4e ( 1 W0,1 + 2 W1,0 ). In this case, the total resistance can be interpreted as two resistances in series with transition loops |±1 → |0 → |±1 in each subwell 16 , as shown in Fig. 1(b).…”

“…The spin tunneling was also predicted to be determined by the identification of the fake resonances in current and noise spectroscopy 15 . Recently, an interesting project to detect the QTM was the observation of the Berry-phase blockade of the stationary current in the sequential tunneling for the SMM placed between oppositely spin-polarized source and drain leads 16 .…”

Spin nutation effects in molecular nanomagnet–superconductor tunnel junctions

“…The electronic transport through magnetic molecules connected to metallic leads have been investigated by extensive theoretical works. The different aspects of the molecular nanomagnets such as the effect of the exchange coupling between spins of conduction electrons and the spin of the molecular nanomagnets [14] have been studied as well as the Coulomb blockade in a transport through a molecular nanomagnet weakly coupled to a magnetic and a nonmagnetic lead [15], the possibility of writing, storing, and reading spin information in memory devices [16], the Kondo effect in transport through a single molecular nanomagnet strongly coupled to two metallic electrodes [17], effects of spin Berry phase on the electron tunneling [18], magnetic switching of the molecular nanomagnets' spin by a spin-polarized current [19], the tunneling magnetoresistance [20] and the effect on the transport of a soft vibrating mode of the molecule [21]. The current through the precessing molecular nanomagnet connected to the metallic contacts has been obtained by considering the molecular magnet as a classical spin [22].…”