arXiv subjects

Masaru Onoda

Publications and source records attributed to Masaru Onoda.

23 records · Page 2Linked to original sources

arXiv2001

Effective mass staircase and the Fermi liquid parameters for the fractional quantum Hall composite fermions

Effective mass of the composite fermion in the fractional quantum Hall system, which is of purely interaction originated, is shown, from a numerical study, to exhibit a curious nonmonotonic behavior with a staircase correlated with the number (=2,4,...) of attached flux quanta. This is surprising since the usual composite-fermion picture predicts a smooth behavior. On top of that, significant interactions are shown to exist between composite fermions, where the excitation spectrum is accurately reproduced in terms of Landau's Fermi liquid picture with negative (i.e., Hund's type) orbital and spin exchange interactions.

cond-mat.mes-hall↗

arXiv1999

Excitation spectrum and effective mass of the even-fraction quantum Hall liquid

To probe the nature of the even-fraction quantum Hall system, we have investigated the low-lying excitation spectrum by means of exact diagonalization for finite systems. We have found (i) a striking one-to-one correspondence (i.e., a shell structure) between the spectrum and those for free (composite) fermions, (ii) a surprisingly straight scaling plot for the excitation energy that gives a zero gap (metal) in the thermodynamic limit, (iii) the effective mass evaluated from the scaling becoming heavier for filling factor = 1/2, 1/4, 1/6, but (iv) some deviations from the single-mode or the Hartree-Fock composite fermion approximation as well.

cond-mat.mes-hall↗

arXiv1999

Spin-gap effect on resistivity in the t-J model

We calculate the spin-gap effect on dc resistivity in the t-J model of high-$T_{\rm c}$ cuprates by using the Ginzburg-Landau theory coupled with a gauge field as its effective field theory to get $ρ(T) \propto T \{1-c\:(T^* -T)^d \}$, where $T^*$ is the spin-gap onset temperature. By taking the compactness of massive gauge field into account, the exponent $d$ deviates from its mean-field value 1/2 and becomes a nonuniversal $T$-dependent quantity, which improves the correspondence with the experiments.

cond-mat.str-el↗

arXiv1996

Instability of the Non-Fermi-Liquid Fixed Point in the Dissipative Gauge Theory of Fermions (I)Impurity Effects

We study a dissipative gauge theory of nonrelativistic fermions in 2+1 dimensions at zero temperature by the Wilsonian renormalization-group method. In this theory, we incorporate in the fermion propagator a new term of the form $ i κ\cdot\sign(ω)$ (where $κ$ is a parameter and $ω$ is the fermion frequency), which is usually induced by impurity effects. In the previous papers, we studied this system for $κ= 0$, and showed that there exists a non-Fermi-liquid infrared fixed point. In this paper, we address the question whether this non-Fermi-liquid behavior remains stable or not in the presence of impurity effects, i.e., the $κ$ term. Our results show that the non-Fermi-liquid fixed point is unstable for $κ\neq 0$ and an effective gauge coupling constant tends to vanish at low energies. However, in intermediate energy scales, the behavior of correlation functions for $κ\neq 0$ is controlled by the non-Fermi-liquid fixed point at $κ=0$, i.e., a crossover phenomenon appears. Physical implications of this phenomenon are discussed.

cond-mat.str-el↗

arXiv1993

Cancellation of unphysical gauge and ghost degrees of freedom in backreaction

We study the U(1) Higgs model in spacetime-dependent background fields (a background metric and a background scalar field). Particle creation can occur because of the time-dependence of these background fields. In gauge theories, there is a unphysical sector and consequently unphysical particles may be produced. However, it is shown that produced unphysical particles have no contribution to backreaction to background fields.

hep-th↗