This study focuses on the synthesis of titanium dioxide (TiO2) nanoparticles (NP) using both chemical and green synthesis methods to evaluate their effectiveness in stain removal when applied to fabrics. The research aims to compare the detergency properties of TiO2 nanoparticles synthesized through conventional chemical techniques and eco-friendly approaches. The performance of these nanoparticles is assessed based on their ability to break down stains, highlighting their potential for textile treatment and environmental cleaning. The findings emphasize the advantages of green synthesis, contributing to sustainable and efficient fabric care solutions.
Transport of massless Dirac fermions in graphene monolayers is analyzed in the presence of a combination of singular magnetic barriers and applied electrostatic potential. Extending a recently proposed (J Phys. Cond. Matt. Vol 21, 292204 (2009)) analogy between the transmission of light through a medium with modulated refractive index and electron transmission in graphene through singular magnetic barriers to the present case, we find the addition of a scalar potential profoundly changes the transmission. We calculate the quantum version of the Goos-Hänchen shift that the electron wave suffers upon being totally reflected by such barriers. The combined electric and magnetic barriers substantially modify the band structure near the Dirac point. This affects transport near the Dirac point significantly and has important consequences for graphene-based electronics.
This is a 20% excerpt of the manuscript entitled Nanomagnetism in Otherwise Nonmagnetic Materials which has been reviewed and approved for the publication in Handbook of Nanophysics (HNP), 7 Volumes, 300 Chapters Klaus D. Sattler, Editor, Taylor&Francis Publisher (CRC Press). In the present version the Introduction, Tutorial, Figures, Tables, critical analysis and Conclusions are omitted. The manuscript may serve as a source of references. The 20% excerpt is placed on cond-mat ArXiv under the permission of Taylor & Francis Group LLC.
Recent scanning tunnelling microscopy (STM) experiments on underdoped cuprates have displayed modulations in the local electronic density of states which are centered on a Cu-O-Cu bond (Kohsaka et. al., cond-mat/0703309). As a paradigm of the pinning of such bond-centered ordering in strongly correlated systems, we present the theory of valence bond solid (VBS) correlations near a single impurity in a square lattice antiferromagnet. The antiferromagnet is assumed to be in the vicinity of a quantum transition from a magnetically ordered Neel state to a spin-gap state with long-range VBS order. We identify two distinct classes of impurities: i) local modulation in the exchange constants, and ii) a missing or additional spin, for which the impurity perturbation is represented by an uncompensated Berry phase. The `boundary' critical theory for these classes is developed: in the second class we find a `VBS pinwheel' around the impurity, accompanied by a suppression in the VBS susceptibility. Implications for numerical studies of quantum antiferromagnets and for STM experiments on the cuprates are noted.
We present a solution for the stationary state of an asymmetric exclusion model with sequential update and open boundary conditions. We solve the model exactly for random hopping in both directions by applying a matrix-product formalism which was recently used to solve the model with sublattice-parallel update (Hinrichsen H 1995 Weizmann Inst. Preprint cond-mat/9512172). It is shown that the matrix-algebra describing the sequential update and sublattice-parallel update are identical and can be mapped onto the random sequential case treated by Derrida et al (Derrida B, Evans M R, Hakim V and Pasquier V 1993 J. Phys. A: Math. Gen. 26 1493).
In a previous Letter (cond-mat/0106565), Goh et al have presented a numerical study of the load--or betweenness centrality--distribution in a scale-free network whose degree distribution follows a power law with a tunable exponent $\gamma$. They showed that the load $\ell$ is distributed according to a power-law with exponent $\delta$. The authors claimed that $\delta$ is universal, ie. independent of the exponent $\gamma$. In this comment, we use two different ways of checking numerically this universality and we show that it does not hold.
A contradiction of the Little-Parks experiment with the Ohm's law and other fundamental laws is explained. This explanation shows that the Little-Parks oscillations of the loop resistance are an experimental evidence of a direct (non-chaotic) Brownian motion. The Langevin force is connected with a change of the momentum circulation of superconducting pairs because of the quantization. Its average value can be non-zero because of the quantization. The existence of a direct Brownian motion contradicts to the principle on which the second law of thermodynamic is based. Therefore the Little-Parks experiment is evidence of a possibility of violation of the second law. In the last years other authors have stated also violation of the second law in different quantum systems: A.E.Allahverdyan and Th.M.Nieuwenhuizen, PRL 85, 1799 (2000); cond-mat/0011389; V.Capec and J.Bok, Czech.J. of Phys. 49, 1645 (1999); cond-mat/0012056; Physica A 290, 379 (2001); P. Weiss, Science News, 158, 234 (2000).
Abstract We show that the conformally invariant boundary conditions for the three-state Potts model are exhausted by the eight known solutions. Their structure is seen to be similar to the one in a free field theory that leads to the existence of D-branes in string theory. Specifically, the fixed and mixed boundary conditions correspond to Neumann conditions, while the free boundary condition and the new one recently found by Affleck et al. [Boundary critical phenomena in the three-state Potts model, preprint cond-mat/9804117] have a natural interpretation as Dirichlet conditions for a higher-spin current. The latter two conditions are governed by the Lee–Yang fusion rules. These results can be generalized to an infinite series of non-diagonal minimal models, and beyond.
A non-perturbative treatment is developed for the dephasing produced by the shot noise of a one-dimensional electron channel. It is applied to two systems: a charge qubit and the electronic Mach–Zehnder interferometer (MZI), both of them interacting with an adjacent partitioned electronic channel acting as a detector. We find that the visibility (interference contrast) can display oscillations as a function of detector voltage and interaction time. This is a unique consequence of the non-Gaussian properties of the shot noise, and only occurs in the strong coupling regime, when the phase contributed by a single electron exceeds π. The resulting formula reproduces the recent surprising experimental observations reported in (I Neder et al 2006 Preprint cond-mat/0610634), and indicates a general explanation for similar visibility oscillations observed earlier in the MZI at large bias voltage. We explore in detail the full pattern of oscillations as a function of coupling strength, voltage and time, which might be observable in future experiments.
We introduce and study an XY-type model of thermal and quantum phase fluctuations in a two-dimensional correlated lattice d-wave superconductor based on the QED3 effective theory of high temperature superconductors. General features of and selected results obtained within this model were reported earlier in an abbreviated format (Z. Tesanovic, cond-mat/0405235). The model is geared toward describing not only the long distance but also the intermediate lengthscale physics of underdoped cuprates. In particular, we elucidate the dynamical origin and investigate specific features of the Cooper pair charge-density-wave (CPCDW), which we argue is the state behind the periodic charge density modulation discovered in recent STM experiments. We illustrate how Mott-Hubbard correlations near half-filling suppress superfluid density and favor an incompressible state which breaks translational symmetry of the atomic lattice. We show how the formation of the CPCDW in such a strongly quantum fluctuating superconductor can be understood as an Abrikosov-Hofstadter problem in a type-II dual superconductor, with the role of the dual magnetic field played by the electron density. The resulting Abrikosov lattice of dual vortices translates into the periodic modulation of the Bogoliubov-deGennes gap function and the electronic density. We compute detailed signatures of various Abrikosov-Hofstadter dual vortex arrays in the single-particle local tunneling density of states. A 4x4 checkerboard-type modulation pattern naturally arises as an energetically favored ground state at and near the x = 1/8 doping and produces good agreement with experimental observations.
Abstract We studied, strongly correlated states in triangular artificial atoms. Symmetry-driven orbital degeneracy of the single particle states can give rise to an SU (4) Kondo state with entangled orbital and spin degrees of freedom, and a characteristic phase shift δ =π/4. Upon application of a Zeeman field, a purely orbital Kondo state is formed with somewhat smaller Kondo temperature and a fully polarized current through the device. The Kondo temperatures are in the measurable range. The triangular atom also provides a tool to systematically study the singlet–triplet transitions observed in recent experiments [Phys. Rev. Lett., 88 (2002) 126803, cond-mat/0208268 (2002)].
Abstract We consider a two-dimensional spin system in a honeycomb lattice configuration that exhibits anyonic and fermionic excitations [Kitaev, cond-mat/0506438]. The exact spectrum that corresponds to the translationally invariant case of a vortex-lattice is derived from which the energy of a single pair of vortices can be estimated. The anyonic properties of the vortices are demonstrated and their generation and transportation manipulations are explicitly given. A simple interference experiment with six spins is proposed that can reveal the anyonic statistics of this model.
Abstract This paper surveys the physics of systems proximate to Mott insulators, and presents a classification using conventional and topological order parameters. This classification offers a valuable perspective on a variety of conducting correlated electron systems, from the cuprate superconductors to the heavy fermion compounds. Connections are drawn, and distinctions made, between collinear/non-collinear magnetic order, bond order, neutral spin 1/2 excitations in insulators, electron Fermi surfaces which violate Luttinger’s theorem, fractionalization of the electron, and the fractionalization of bosonic collective modes. Two distinct categories of Z 2 gauge theories are used to describe the interplay of these orders. Experimental implications for the cuprates are briefly noted, but these appear in more detail in a companion review paper (S. Sachdev, cond-mat/0211005).
We study the extended Hubbard model on a triangular lattice near doping x = (1/3), which may be relevant for the recently discovered superconductor NaxCoO2·yH2O. By generalizing this model to N fermionic species, we formulate a meanfield description in the limit of large N. In meanfield, we find two possible phases: a renormalized Fermi liquid and a sqrt(3)×sqrt(3) charge density wave state. The transition between the two phases is driven by increasing the nearest-neighbor repulsion and is found to be first order for doping x = (1/3), but occurs close to the point of the local instability of the uniform liquid. We also study fluctuations about the uniform meanfield state in a systematic 1/N expansion, focusing on the residual interaction of quasiparticles and possible superconducting instabilities due to this interaction. Upon moving towards the charge density wave instability, the increasing charge fluctuations favor a particular f-wave triplet state. (This state was recently discussed by Tanaka et al., cond-mat/0311266.) We also report a direct Gutzwiller wave function study of the spin-(1/2) model.
We note that the model discussed in the communication of S. Bornholdt and H. Ebel (World Wide Web scaling exponent from Simon's 1955 model, cond-mat/0008465) is the particular case of the model considered and solved exactly in our paper, cond-mat/0004434. These models may be used for estimation of the order of the deviation of the scaling exponent from 2 both for the distributions of incoming links and links coming out from nodes but not for the obtaining some specific values of the exponents from the WWW growth data. We emphasize that, unlike the statement of Bornholdt and Ebel, both the network under consideration and the model of Barab\'{a}si and Albert provide quite equal possibilities for individual growth. There is no great difference between them in this respect. The resulting distributions for individual nodes and arising scaling relations have been obtained in our paper, cond-mat/0004434. We discuss briefly the modern state of art in the physics of the evolving networks and the great role of the general principle -- {\em popularity is attractive} -- in the self-organization of complex communications networks, in physics of nonequilibrium phenomena, and in Nature.