4He Luttinger liquid in nanopores

We study the low-temperature properties of a 4He fluid confined in nanopores, using large-scale quantum Monte Carlo simulations with realistic He-He and He-pore interactions. In the narrow-pore limit, the system can be described by the quantum hydrodynamic theory known as Luttinger liquid theory with a large Luttinger parameter, corresponding to the dominance of solid tendencies and strong susceptibility to pinning by a periodic or random potential from the pore walls. On the other hand, for wider pores, the central region appears to behave like a Luttinger liquid with a smaller Luttinger parameter, and may be protected from pinning by the wall potential, offering the possibility of experimental detection of a Luttinger liquid.     

Three fluid hydrodynamics of superfluid3He

TheA ₂-transition from theA ₁ to theA-phase is the only known transition that seperates a state with a broken relative symmetry from one in which both constituent symmetries are independently broken. Therefore a question of interest here is what the Goldstone mode of this transition is. Employing two different points of view, one for its rigor and the other because of its plausible physical picture, a three fluid hydrodynamics is derived and employed to show that, with a grain of salt, theA ₂-transition can be taken as marked by the onset of spin wave in a restricted geometry and by that of second sound generally. More quantitatively, the transition of the Goldstone modes takes place below theA ₂ transitional temperature when the Leggett frequency is approached and is caused by two competing effects, hybridization and dispersion. In a fourth sound geometry these effects should be experimentally well accessible.     

Possible low-temperature nearly frictionless states of locally amorphous solid <Superscript>4</Superscript>He in nanopores

It has been recently reported that there might be amorphous solid ⁴He formed in around 4.7 ± 0.15 nm pore [J. Bossy, T. Hansen, H.R. Glyde, Phys. Rev. B 81, 184507 (2010)]. By treating the solid ⁴He in confined nanopores at very low temperature locally as an amorphous matter and using the verified transition-state model together with the specific activation energy and volume, we can observe a sudden change of the shearing stresses (which relate to the transport resistance) at corresponding onset temperature of locally amorphous solid ⁴He considering the role of holes or defects. We found that there might be possible almost very-low flow-resistance transport of locally amorphous solid ⁴He confined in nanopores at temperature ∼ 0.1 K after intensive calculations.     

Superfluidity of 4He in one and three dimensions realized in nanopores

Superfluidity in one and three dimensions has been studied for 4He fluid films adsorbed in nanopores which are straight channels and three-dimensionally connected pores, respectively. We observed the superfluid in one and three dimensions where thermal phonon wavelengths are much longer than the channel diameter and the period of the pore connection, respectively, and found that the superfluid onset depends on the pore connection. In the straight channels, the observed superfluid density disappears at a temperature far below the heat capacity anomaly of the Ginzburg-Landau transition, while in the pores connected in three dimension, the adsorbed 4He films show an evident three-dimensional transition where the superfluid onset occurs at the heat capacity peak.     

Model of quantum criticality in He3 bilayers adsorbed on graphite

Recent experiments on He3 bilayers adsorbed on graphite have shown striking quantum critical properties at the point where the first layer localizes. We model this system with the Anderson lattice plus interlayer Coulomb repulsion in two dimensions. Assuming that quantum critical fluctuations come from a vanishing of the effective hybridization, we can reproduce several features of the system, including the apparent occurrence of two quantum critical points, the variation of the effective mass and coherence temperature with coverage.     

Polaronic effects in one-dimensional quantum antidot arrays

We study the effect of polaronic corrections arising from theelectron-longitudinal optical phonon interaction on the energyspectrum of a two-dimensional electron system with a one-dimensionalperiodic antidot array geometry created by a weak electrostaticmodulation potential, and subjected to a weak magnetic fieldmodulation as well as a uniform strong perpendicular staticmagnetic field. To incorporate the effects of electron-phononinteractions within the framework of Fröhlich polaron theory, wefirst apply a displaced-oscillator type unitary transformation todiagonalise the relevant Fröhlich Hamiltonian, and we thendetermine the parameters of this transformation together with theparameter included in the electronic trial wave function . On thebasis of this technique, it has been shown that the polaroniccorrections have non-negligible effects on the electronic spectrumof a two-dimensional electron system with a quantum antidot array,since switching such an interaction results in shifting thedegeneracy restoring points of Landau levels wherein the flatbandcondition is fulfilled, thus suppressing the Weiss oscillations.     

Rashba electron transport in one-dimensional quantum waveguides

The properties of Rashba wave function in the planar one-dimensional waveguide are studied, and the following results are obtained. Due to the Rashba effect, the plane waves of electron with the energy E divide into two kinds of waves with the wave vectors k 1 =k 0 +k δ and k 2 =k 0 -k δ , where k δ is proportional to the Rashba coefficient, and their spin orientations are +π/2 (spin up) and -π/2 (spin down) with respect to the circuit, respectively. If there is gate or ferromagnetic contact in the circuit, the Rashba wave function becomes standing wave form exp(±ik δ l)sin[k 0 (l-L)], where L is the position coordinate of the gate or contact. Unlike the electron without considering the spin, the phase of the Rashba plane or standing wave function depends on the direction angle θ of the circuit. The travel velocity of the Rashba waves with the wave vector k 1 or k 2 are the same hk0/m * . The boundary conditions of the Rashba wave functions at the intersection of circuits are given from the continuity of wave functions and the conservation of current density. Using the boundary conditions of Rashba wave functions we study the transmission and reflection probabilities of Rashba electron moving in several structures, and find the interference effects of the two Rashba waves with different wave vectors caused by ferromagnetic contact or the gate. Lastly we derive the general theory of multiple branches structure. The theory can be used to design various spin polarized devices.     

Evidence for a Mott-Hubbard transition in a two-dimensional 3He fluid monolayer

The heat capacity and magnetization of a fluid 3He monolayer adsorbed on graphite plated with a bilayer of HD have been measured in the temperature range 1-60 mK. Approaching the density at which the monolayer solidifies into a sqrt[7]xsqrt[7] commensurate solid, we observe an apparent divergence of the effective mass and magnetization corresponding to a T=0 Mott-Hubbard transition between a 2D Fermi liquid and a magnetically disordered solid. The observations are consistent with the Brinkman-Rice-Anderson-Vollhardt scenario for a metal-insulator transition. We observe a leading order T2 correction to the linear term in heat capacity.     

Photoconductance of a one-dimensional quantum dot

The ac-transport properties of a one-dimensional quantum dot with non-Fermi liquid correlations are investigated. It is found that the linear photoconductance is drastically influenced by the interaction. While for weak interaction it shows peak-like resonances, in the strong interaction regime it assumes a step-like behavior. In both cases the photo-transport provides precise informations about the quantized plasmon modes in the dot. Temperature and voltage dependences of the sideband peaks are treated in detail. Characteristic Luttinger liquid power laws are found. Received 23 October 2001     

Variational model for one-dimensional quantum magnets

A new variational technique for investigation of the ground state and correlation functions in 1D quantum magnets is proposed. A spin Hamiltonian is reduced to a fermionic representation by the Jordan–Wigner transformation. The ground state is described by a new non-local trial wave function, and the total energy is calculated in an analytic form as a function of two variational parameters. This approach is demonstrated with an example of the XXZ-chain of spin-1/2 under a staggered magnetic field. Generalizations and applications of the variational technique for low-dimensional magnetic systems are discussed.     

Discrete-time quantum walks on one-dimensional lattices

In this paper, we study discrete-time quantum walks on one-dimensional lattices. We find that the coherent dynamics depends on the initial states and coin parameters. For infinite size of lattices, we derive an explicit expression for the return probability, which shows scaling behavior P(0, t) ~ t ^-1 and does not depends on the initial states of the walk. In the long-time limit, the probability distribution shows various patterns, depending on the initial states, coin parameters and the lattice size. The time-averaged probability mixes to the limiting probability distribution in linear time, i.e., the mixing time M _ε is a linear function of N (size of the lattices) for large values of thresholds ϵ. Finally, we introduce another kind of quantum walk on infinite or even-numbered size of lattices, and show that by the method of mathematical induction, the walk is equivalent to the traditional quantum walk with symmetrical initial state and coin parameter.     

Equilibration of a one-dimensional quantum liquid

We review some of the recent results on equilibration of one-dimensional quantum liquids. The low-energy properties of these systems are described by the Luttinger liquid theory, in which the excitations are bosonic quasiparticles. At low temperatures, the relaxation of the gas of excitations toward full equilibrium is exponentially slow. In electronic Luttinger liquids, these relaxation processes involve backscattering of electrons and give rise to interesting corrections to the transport properties of one-dimensional conductors. We focus on the phenomenological theory of the equilibration of a quantum liquid and obtain an expression for the relaxation rate in terms of the excitation spectrum.     

Source transformation device formed by one-dimensional photonic crystal

Photonic bandgap structures can also be utilized for the realization of transformational optical devices like metamaterials. In this Letter, the possibility of cylindrical to plane wave source transformation in an open cavity formed by one dimensional photonic crystal is demonstrated. It is observed that the gap solitary wave behavior at the near-bandgap regime is fair enough to produce highly directional plane waves out of the point source placed inside the open cavity. The limitations of such a source transformation device are governed by the strength of the bandgap that decides the amplitude of the emitted plane waves.