Spin Berry phase in the Fermi arc states

Unusual electronic property of a Weyl semi-metallic nanowire is revealed. Its band dispersion exhibits multiple subbands of partially flat dispersion, originating from the Fermi arc states. Remarkably, the lowest energy flat subbands bear a finite size energy gap, implying that electrons in the Fermi arc surface states are susceptible of the spin Berry phase. This is shown to be a consequence of spin-to-surface locking in the surface electronic states. We verify this behavior and the existence of spin Berry phase in the low-energy effective theory of Fermi arc surface states on a cylindrical nanowire by deriving the latter from a bulk Weyl Hamiltonian. We point out that in any surface state exhibiting a spin Berry phase pi, a zero-energy bound state is formed along a magnetic flux tube of strength, hc/(2e). This effect is highlighted in a surfaceless bulk system pierced by a dislocation line, which shows a 1D chiral mode along the dislocation line.Comment: 9 pages, 9 figure

Discontinuous Transition from a Real Bound State to Virtual Bound State in a Mixed-Valence State of SmS

Golden SmS is a paramagnetic, mixed-valence system with a pseudogap. With increasing pressure across a critical pressure Pc, the system undergoes a discontinuous transition into a metallic, anti-ferromagnetically ordered state. By using a combination of thermodynamic, transport, and magnetic measurements, we show that the pseudogap results from the formation of a local bound state with spin singlet. We further argue that the transition Pc is regarded as a transition from an insulating electron-hole gas to a Kondo metal, i.e., from a spatially bound state to a Kondo virtually bound state between 4f and conduction electrons.Comment: 5 pages, 5 figure

Strong quasi-particle tunneling study in the paired quantum Hall states

The quasi-particle tunneling phenomena in the paired fractional quantum Hall states are studied. A single point-contact system is first considered. Because of relevancy of the quasi-particle tunneling term, the strong tunneling regime should be investigated. Using the instanton method it is shown that the strong quasi-particle tunneling regime is described as the weak electron tunneling regime effectively. Expanding to the network model the paired quantum Hall liquid to insulator transition is discussed

Characterization of two-dimensional fermionic insulating states

Inspired by the duality picture between superconductivity and insulator in two spatial dimension, we conjecture that the order parameter, suitable for characterizing 2D fermionic insulating state, is the disorder operator, usually known in the context of statistical transformation. Namely, the change of the phase of the disorder operator along a closed loop measures the particle density accommodating inside this loop. Thus, identifying this (doped) particle density with the dual counterpart of the magnetic induction in 2D SC, we can naturally introduce the disorder operator as the dual order parameter of 2D insulators. The disorder operator has a branch cut emitting from this ``vortex'' to the single infinitely far point. To test this conjecture against an arbitrary 2D lattice models, we have chosen this branch cut to be compatible with the periodic boundary condition and obtain a general form of its expectation value for non-interacting metal/insulator wavefunction, including gapped mean-field order wavefunction. Based on this expression, we observed analytically that it indeed vanishes for a wide class of band metals in the thermodynamic limit. In insulating states, on the other hand, it is quantified by the localization length or the real-valued gauge invariant 2-from dubbed as the quantum metric tensor

Disorder-Induced Multiple Transition involving Z2 Topological Insulator

Effects of disorder on two-dimensional Z2 topological insulator are studied numerically by the transfer matrix method. Based on the scaling analysis, the phase diagram is derived for a model of HgTe quantum well as a function of disorder strength and magnitude of the energy gap. In the presence of sz non-conserving spin-orbit coupling, a finite metallic region is found that partitions the two topologically distinct insulating phases. As disorder increases, a narrow-gap topologically trivial insulator undergoes a series of transitions; first to metal, second to topological insulator, third to metal, and finally back to trivial insulator. We show that this multiple transition is a consequence of two disorder effects; renormalization of the band gap, and Anderson localization. The metallic region found in the scaling analysis corresponds roughly to the region of finite density of states at the Fermi level evaluated in the self-consistent Born approximation.Comment: 5 pages, 5 figure

Drag forces on inclusions in classical fields with dissipative dynamics

We study the drag force on uniformly moving inclusions which interact linearly with dynamical free field theories commonly used to study soft condensed matter systems. Drag forces are shown to be nonlinear functions of the inclusion velocity and depend strongly on the field dynamics. The general results obtained can be used to explain drag forces in Ising systems and also predict the existence of drag forces on proteins in membranes due to couplings to various physical parameters of the membrane such as composition, phase and height fluctuations.Comment: 14 pages, 7 figure

The edge state network model and the global phase diagram

The effects of randomness are investigated in the fractional quantum Hall systems. Based on the Chern-Simons Ginzburg-Landou theory and considering relevant quasi-particle tunneling, the edge state network model for the hierarchical state is introduced and the plateau-plateau transition and liquid-insulator transition are discussed. This model has duality which corresponds to the relation of the quantum Hall liquid phase and the Hall insulating phase and reveals a mechanism in the weak coupling regime.Comment: 5 page RevTe

Lattice Defects of Quartz Induced by Fast Neutron Irradiation

Lattice defects in natural and synthetic quartz crystals induced by an exposure to fast neutron irradiation ranging from 1×10^?1.5×10^ nvt were studied by x-ray and transmission electron microscopy methods. A quantitative strain analysis based on the x-ray divergent beam method yielded the principal strains and their directions as a function of radiation dose. Major differences with regard to the magnitude and directions of the strains were found between crystals cut parallel to the basal (00.1) plane (z-cut) and those cut perpendicular to it (x-cut), while virtually no difference was observed between natural and synthetic crystals. A close correlation was established between the alignment of clusters rich in interstitial silicon atoms directly observed by transmission electron microscopy, and the strain distribution disclosed by the x-ray method. The results were interpreted in terms of a mechanism of dynamic crowdions giving rise to the formation of clusters of interstitial atoms aligned in directions relative to the open screw channels of the quartz structure. At large radiation doses interaction of the densely populated clusters occurred which appeared to be aided by thermal spikes and which resulted in the formation of a stable network of lattice defects. Crystals irradiated 1×10^ nvt still exhibited a considerable degree of crystallinity, as evidenced by the extinction contour lines seen in the electron microscope