相关论文: Quantum Tunneling in Half-Integer Spin Systems

The spin one half molecular system V15 shows no barrier against spin reversal. This makes possible direct phonon activation between the two levels. By tuning the field sweeping rate and the thermal coupling between sample and thermal…

The so-called V15 molecule is formed of 15 spins 1/2 antiferromagnetically coupled. The resultant spin is equal to 1/2. Contrary to what is expected at first sight, this half-integer spin is gapped. We show that this is a consequence of the…

We study the ultrafast dynamic process in photoexcited systems and find that the Franck-Condon or Landau-Zener tunneling between the photoexcited state and the ground state is abruptly blocked with increasing the state coupling from…

Since the pioneering works by Landau, Zener, St\"uckelberg, and Majorana (LZSM), it has been known that driving a quantum two-level system results in tunneling between its states. Even though the interference between these transitions is…

The Landau-Zener transition is a fundamental concept for dynamical quantum systems and has been studied in numerous fields of physics. Here we present a classical mechanical model system exhibiting analogous behaviour using two inversely…

Motivated by recent realizations of qubits with a readout by macroscopic quantum tunneling in a Josephson junction, we study the problem of barrier penetration in presence of coupling to a spin-${1\over 2}$ system. It is shown that when the…

Kramers degeneracy theorem is one of the basic results in quantum mechanics. According to it, the time-reversal symmetry makes each energy level of a half-integer spin system at least doubly degenerate, meaning the absence of transitions or…

Single-molecule magnets facilitate the study of quantum tunneling of magnetization at the mesoscopic level. The spin-parity effect is among the fundamental predictions that have yet to be clearly observed. It is predicted that quantum…

Two antiferromagnetically coupled tunneling systems is a minimal model exhibiting the effect of quantum-mechanical phase in the Landau-Zener effect. It is shown that the averaged staying probability oscillates vs resonance shift between the…

We investigate the Landau-Zener tunneling (LZT) of a self-interacting two-level system in which the coupling between the levels is nonreciprocal. In such a non-Hermitian system, when the energy bias between two levels is adjusted very…

We study Landau-Zener macroscopic quantum transitions in ferromagnetic metal nanoparticles containing on the order of 100 atoms. The model that we consider is described by an effective giant-spin Hamiltonian, with a coupling to a random…

We develop a general theory of Landau-Zener (LZ) tunneling in a two-level system with amplitude-dependent, sign-reversible nonlinear coupling, distinguishing it fundamentally from conventional on-site nonlinearity. Through a combination of…

The quantum mechanical counterpart of the famous Stoner-Wohlfarth model -- an easy-axis magnet in a tilted magnetic field -- is studied theoretically and through simulations, as a function of the spin-size $S$ in a sweeping longitudinal…

We monitor the Landau-Zener dynamics of a single-ion magnet in a spin-transistor geometry. For increasing field-sweep rates, the spin reversal probability shows increasing deviations from that of a closed system. In the low-conductance…

Time-dependent nonequilibrium properties of a strongly correlated electron system driven by large electric fields is obtained by means of solving the time-dependent Schr\"odinger equation for the many-body wave function numerically in one…

We present a detailed analysis of the Landau-Zener problem for an interacting Bose-Einstein condensate in a time-varying double-well trap, especially focussing on the relation between the full many-particle problem and the mean-field…

A Mn4 single-molecule magnet (SMM), with a well isolated spin ground state of S = 9/2, is used as a model system to study Landau-Zener (LZ) tunneling in the presence of weak intermolecular dipolar and exchange interactions. The anisotropy…

A nonlinear Landau-Zener model was proposed recently to describe, among a number of applications, the nonadiabatic transition of a Bose-Einstein condensate between Bloch bands. Numerical analysis revealed a striking phenomenon that…

Tunneling of electrons into a two-dimensional electron system is known to exhibit an anomaly at low bias, in which the tunneling conductance vanishes due to a many-body interaction effect. Recent experiments have measured this anomaly…

Adiabatic processes in the quantum Ising model and the anisotropic Heisenberg model are discussed. The adiabatic processes are assumed to consist in the slow variation of the strength of the magnetic field that environs the spin-systems.…