Quasi-Bound States of Two Magnons in the Spin-1/2XXZ Chain

We study two-magnon Bethe states in the spin-1/2 XXZ chain. The string hypothesis assumes that complex rapidities of the bound states take special forms. It is known, however, that there exist “non-string states,” which substantially disagrees with the string hypothesis. In order to clarify their nature, we study the large-N behavior of solutions of the Bethe-Ansatz equations to obtain explicit forms of typical Bethe states, where N is the length of the chain, and apply the scaling analysis (the multifractal analysis) to the Bethe states. It turns out that the non-string states contain “quasi-bound” states, which in some sense continuously interpolate between extended states and localized states. The “quasi-bound” states can be distinguished from known three types of states, i.e., extended, localized, and critical states. Our results indicate that there might be a need to reconsider the standard classification scheme of wavefunctions.     

Invar effects in Zr0.7Nb0.3Fe2

A thermal expansion anomaly similar to that of the invar alloy was observed in a Laves phase intermetallic compound, Zr_0.7Nb_0.3Fe₂. This anomaly is explained as a result of a large spontaneous volume magnetostriction. Magnetic properties and magnetovolume effects of this material are discussed on the basis of the band of ferromagnetism.     

Cluster approximation for an infinite-dimensional determinant

A systematic approximation scheme is proposed for the evaluation of the determinant of an infinite-dimensional matrix which is encountered with, for example, in the theoretical study of Fermion aggregate. This scheme is compatible with the cluster variation method for Ising problems since the combination of the two methods ensures that the total probability is unity. It is useful for the extension of the Gutzwiller variation method in the electron correlation problem.     

Thermoelectric power of Y(Mn1−xAlx)2

Electrical resistivity and thermoelectric power of Y(Mn_1−xAl_x2 and (Y_1−xSc_x)Mn₂ were measured from 2 to room temperature. Anomalous behavior of the thermoelectric power of YMn₂ disappears rapidly with the increase of Al content in Y(Mn_1−xAl_x)₂. Based upon spin fluctuations of the itinerant antiferromagnetism of the samples, the anomaly of the thermoelectric power is discussed.     

NMR study of nearly itinerant antiferromagnetic Y1−xScxMn2

The NMR investigation of Y_0.97Sc_0.03Mn₂ has revealed that this compound remains paramagnetic down to 4.2 K. The nuclear spin-lattice relaxation rates, 1/T₁, of ⁵⁵Mn and ⁴⁵Sc in Y_0.97Sc_0.03Mn₂ show the T dependence as predicted from the self-consistent renormalization (SCR) theory of spin fluctuations for nearly antiferromagnetic metals.     

Ab initio study of ultrafast photochemical reaction dynamics of phenol blue

Phenol blue (PB) is a primary skeletal structure part of indoaniline dyes and well-known as a solvatochromic dye. It has been recently observed by pump-probe (PP) transient absorption measurements that PB shows ultrafast ground state recovery within a few hundred femtoseconds after photoexcitation. In this work, the ultrafast photochemical reaction mechanism of PB has been investigated using direct ab initio (CASSCF) nonadiabatic molecular dynamics with the trajectory surface hopping (TSH) method. The swarm of trajectories starting from the S1 Franck-Condon (FC) point has mostly shown surface hops (nonadiabatic transitions) from the S1 state to the S0 state at 110-120 fs in the vicinity of an S1/S0 conical intersection and after decay to the S0 state bifurcated into two (Reverse and Forward) directions with almost the same branching ratio and reached the vicinity of the S0 minimum energy point at 200-300 fs, which is in good agreement with the fast time component of the ground state recovery in the PP measurements. After reaching the vicinity of the S0 minimum energy point, the trajectories showed a coherent vibration of bending motion between quinoneimine and aniline rings with a low frequency of 43 cm-1, which presumably corresponds to a coherently photoexcitation-induced vibrational mode with a low frequency recently observed by the PP measurements.