arXiv subjects

Kazusumi Ino

Publications and source records attributed to Kazusumi Ino.

16 recordsLinked to original sources

arXiv2008

Incompressible Liquid, Stripes and Bubbles in rapidly rotating Bose atoms at $ν=1$

We numerically study the system of rapidly rotating Bose atoms at the filling factor (ratio of particle number to vortex number) $ν=1$ with the dipolar interaction. A moderate dipolar interaction stabilizes the incompressible quantum liquid at $ν=1$. Further addition induces a collapse of it. The state after the collapse is a compressible state which has phases with stripes and bubbles. There are two types of bubbles with a different array. We also investigate models constructed from truncated interactions and the models with the three-body contact interaction. They also have phases with stripes and bubbles.

cond-mat.mes-hall↗

arXiv2005

Critical Spectra and Wavefunctions of a One-dimensional Quasiperiodic System

We numerically study a one dimensional quasiperiodic system obtained from two dimensional electrons on the triangular lattice in a uniform magnetic field aided by the multifractal method. The phase diagram consists of three phases: two metallic phases and one insulating phase separated by critical lines with one bicritical point. Novel transitions between the two metallic phases exist. We examine the spectra and the wavefunctions along the critical lines. Several types of level statistics are obtained. Distributions of the band widths $P_B(w)$ near the origin (in the tail) %around the origin (in the tail) have a form $P_B(w) \sim w^β$ ($P_B(w) \sim e^{-γw}$) ($β, γ> 0 $), while at the bicritical point $P_B(w) \sim w^{-β'}$ ($β'>0$). Also distributions of the level spacings follow an inverse power law $P_G(s) \sim s^{- δ}$ ($δ> 0$). For the wavefunctions at the centers of spectra, scaling exponents and their distribution in terms of the $α$-$f(α)$-curve are obtained. The results in the vicinity of critical points are consistent with the phase diagram.

cond-mat.dis-nn↗

arXiv2004

Critical Level Statistics of the Fibonacci Model

We numerically analyze spectral properties of the Fibonacci model which is a one-dimensional quasiperiodic system. We find that the energy levels of this model have the distribution of the band widths $w$ obeys $P_B(w)\sim w^α$ $(w\to 0)$ and $P_B(w) \sim e^{-βw}$ $(w\to\infty)$, the gap distribution $P_G(s)\sim s^{-δ}$ $(s\to 0)$ ($α,β,δ>0$) . We also compare the results with those of multi-scale Cantor sets. We find qualitative differences between the spectra of the Fibonacci model and the multi-scale Cantor sets.

cond-mat.stat-mech↗

arXiv2003

Statistics of Spectra for One-dimensional Quasi-Periodic Systems at the Metal-Insulator Transition

We study spectral statistics of one-dimensional quasi-periodic systems at the metal-insulator transition. Several types of spectral statistics are observed at the critical points, lines, and region. On the critical lines, we find the bandwidth distribution $P_B(w)$ around the origin (in the tail) to have the form of $P_B(w) \sim w^α$ ($P_B(w) \sim e^{-βw^γ}$) ($α, β, γ> 0 $), while in the critical region $P_B(w) \sim w^{-α'}$ ($α' > 0$). We also find the level spacing distribution to follow an inverse power law $P_G(s) \sim s^{- δ}$ ($δ> 0$)

cond-mat↗

arXiv2003

Random Matrix Theory Analysis of Cross Correlations in Financial Markets

We confirm universal behaviors such as eigenvalue distribution and spacings predicted by Random Matrix Theory (RMT) for the cross correlation matrix of the daily stock prices of Tokyo Stock Exchange from 1993 to 2001, which have been reported for New York Stock Exchange in previous studies. It is shown that the random part of the eigenvalue distribution of the cross correlation matrix is stable even when deterministic correlations are present. Some deviations in the small eigenvalue statistics outside the bounds of the universality class of RMT are not completely explained with the deterministic correlations as proposed in previous studies. We study the effect of randomness on deterministic correlations and find that randomness causes a repulsion between deterministic eigenvalues and the random eigenvalues. This is interpreted as a reminiscent of ``level repulsion'' in RMT and explains some deviations from the previous studies observed in the market data. We also study correlated groups of issues in these markets and propose a refined method to identify correlated groups based on RMT. Some characteristic differences between properties of Tokyo Stock Exchange and New York Stock Exchange are found.

cond-mat.stat-mech↗

arXiv2000

Supersymmetry and d-Wave Superconductivity

Motivated by a recent development in the field theory of the fractional quantum Hall effect, we propose a supersymmetric field theoretical model of quantum critical d-wave and (d+id)-wave superconductors. New concept is a composite particle with the supercharge which is formed by electron (hole) and supersymmetric collective configurations of spin and charge. Quantum critical d-wave superconductor is characterized as the condensate of these composite particles.

cond-mat.str-el↗

arXiv2000

Field theory of spin-singlet quantum Hall states

We formulate a field theory for a class of spin-singlet quantum Hall states (the Haldane-Rezayi state and its variants) which have been proposed for the quantized Hall plateaus observed at the second lowest Landau level. A new essential ingredient is a class of super Chern-Simons field. We show that the known properties of the states are consistently described by it. We also give a 2+1 dimensional hierarchical construction. Implications of the proposal are discussed and a new physical picture of composite particles at the second lowest Landau level emerges.

cond-mat.mes-hall↗

arXiv2000

Persistent edge currents for paired quantum hall states

We study the behavior of the persistent edge current for paired quantum Hall states on the cylinder. We show that the currents are periodic with the unit flux $ϕ_0=hc/e$. At low temperatures, they exhibit anomalous oscillations in their flux dependence.The shape of the functions converges to the sawtooth function periodic with $ϕ_0/2$.

cond-mat.mes-hall↗

arXiv1999

Spin-singlet hierarchy in the fractional quantum Hall effect

We show that the so-called permanent quantum Hall states are formed by the integer quantum Hall effects on the Haldane-Rezayi quantum Hall state. Novel conformal field theory description along with this picture is deduced. The odd denominator plateaux observed around $ν=5/2$ are the permanent states if the $ν=5/2$ plateau is the Haldane-Rezayi state. We point out that there is no such hierarchy on other candidate states for $ν=5/2$. We propose experiments to test our prediction.

cond-mat.mes-hall↗

arXiv1999

The Haldane-Rezayi Quantum Hall State and Magnetic Flux

We consider the general abelian background configurations for the Haldane-Rezayi quantum Hall state. We determine the stable configurations to be the ones with the spontaneous flux of $(\Z+1/2) ϕ_0$ with $ϕ_0 = hc/e$. This gives the physical mechanism by which the edge theory of the state becomes identical to the one for the 331 state. It also provides a new experimental consequence which can be tested in the enigmatic $ν=5/2$ plateau in a single layer system.

cond-mat.mes-hall↗

arXiv1998

Persistent Edge Current In the Fractional Quantum Hall Effect

We study the persistent edge current in the fractional quantum Hall effect. We give the grand partition functions for edge excitations of hierarchical states coupled to an Aharanov-Bohm flux and derive the exact formula of the persistent edge current. For $m$-th hierarchical states with $m>1$, it exhibits anomalous oscillations in its flux dependence at low temperatures. The current as a function of flux goes to the sawtooth function with period $ϕ_0/m$ in the zero temperature limit. This phenomenon provides a new evidence for exotic condensation in the fractional quantum Hall effect. We propose experiments of measuring the persistent edge current to confirm the existence of the hierarchy.

cond-mat.mes-hall↗

arXiv1998

Modular Invariants in the Fractional Quantum Hall Effect

We investigate the modular properties of the characters which appear in the partition functions of nonabelian fractional quantum Hall states. We first give the annulus partition function for nonabelian FQH states formed by spinon and holon (spinon-holon state). The degrees of freedom of spin are described by the affine SU(2) Kac-Moody algebra at level $k$. The partition function and the Hilbert space of the edge excitations decomposed differently according to whether $k$ is even or odd. We then investigate the full modular properties of the extended characters for nonabelian fractional quantum Hall states. We explicitly verify the modular invariance of the annulus grand partition functions for spinon-holon states, the Pfaffian state and the 331 states. This enables one to extend the relation between the modular behavior and the topological order to nonabelian cases. For the Haldane-Rezayi state, we find that the extended characters do not form a representation of the modular group, thus the modular invariance is broken.

cond-mat.mes-hall↗

arXiv1998

Tunneling in Paired Fractional Quantum Hall States: Conductance and Andreev Reflection of Non-Abelions

We study the edge transport properties of paired fractional quantum Hall (FQH) states--- the Haldane-Rezayi (HR), Moore-Read (Pfaffian) and Halperin (331) states. A table of exponents is given for the tunneling between the edges of paired FQH states in gated 2D structures and the tunneling into the edge of FQH states from a normal Fermi liquid (N). It is found that HR, Pfaffian and 331 states have different exponents for quasiparticle tunneling. For the tunneling through a FQH-N junction, we propose unusual Andreev reflection processes that may also probe the non-abelian FQH states.

cond-mat↗

arXiv1998

Pairing Effects in the Edge of Paired Quantum Hall States

We study pairing effects in the edge states of paired fractional quantum Hall states by using persistent edge currents as a probe. We give the grand partition functions for edge excitations of paired states (Pfaffian, Haldane-Rezayi, 331) coupling to an Aharanov-Bohm flux and derive the exact formulas of the persistent edge current. We show that the currents are flux periodic with the unit flux $ϕ_0=hc/e$. At low temperatures, they exhibit anomalous oscillations in their flux dependence. The shapes of the functions depend on the bulk topological order. They converge to the sawtooth function with period $ϕ_0/2$ at zero temperature, which indicates pair condensation. This phenomenon provides an interesting bridge between superconductivity in 2+1 dimensions and superconductivity in 1+1 dimensions. We propose experiments of measuring the persistent current at even denominator plateau in single or double layer systems to test our predictions.

cond-mat.mes-hall↗

arXiv1998

Multiple Edge Partition Functions For Fractional Quantum Hall States

We consider the multiple edge states of the Laughlin state and the Pfaffian state. These edge states are globally constrained through the operator algebra of conformal field theory in the bulk. We analyze these constraints by introducing an expression of quantum hall state by the chiral vertex operators and obtain the multiple edge partition functions by using the Verlinde formula.

cond-mat.mes-hall↗

arXiv1997

Chiral Vertices, Fusion Rules and Vacua of Fractional Quantum Hall Systems

Vacua of two dimensional incompressible system, such as Fractional Quantum Hall system, are characterized by rational conformal field theory. We develop a method to express the wavefunctions of those systems in terms of chiral vertices. We formulate quantum mechanics on those expressions, which reveals the underlying simple structure of the conformal field theory discription of FQH systems. Also we argue the recent conjecture of Nayak and Wilczek on the spinor statistics of 2n quasihole state in paired quantum hall system.

cond-mat.mes-hall↗