Point-contact transport properties of strongly correlated electrons on liquid helium

We present transport measurements of a nondegenerate two-dimensional electron system on the surface of liquid helium at a point constriction. The constriction is formed in a microchannel by a split gate beneath the helium surface. The electrostatic energy of the electron system, which depends in part on the electron density, determines the split-gate voltage threshold of current flow through the constriction. Steplike increases in conductance are observed as the confinement strength is reduced. As the Coulomb interaction between electrons is strong, we attribute this effect to the increase in the number of electrons that can pass simultaneously through the constriction. Close to the threshold, single-electron transport is observed.     

Unveiling the nature of three-dimensional orbital ordering transitions: the case of e(g) and t(2g) models on the cubic lattice

We perform large scale finite-temperature Monte Carlo simulations of the classical e(g) and t(2g) orbital models on the simple cubic lattice in three dimensions. The e(g) model displays a continuous phase transition to an orbitally ordered phase. While the correlation length exponent ν ≈ 0.66(1) is close to the 3D XY value, the exponent η ≈ 0.15(1) differs substantially from O(N) values. At T(c) a U(1) symmetry emerges, which persists for T < T(c) below a crossover length scaling as Λ ～ ξ(a), with an unusually small a ≈ 1.3. Finally, for the t(2g) model we find a first order transition into a low-temperature lattice-nematic phase without orbital order.     

Confinement of slave particles in U(1) gauge theories of strongly interacting electrons

We show that slave particles are always confined in U(1) gauge theories of interacting electron systems. Consequently, the low-lying degrees of freedom are different from the slave particles. This is done by constructing a dual formulation of the slave-particle representation in which the no-double-occupancy constraint becomes linear and, hence, soluble. Spin-charge separation, if it occurs, is due to the existence of solitons with fractional quantum numbers in a particular dual action.     

Investigation of spontaneously generated coherence in dressed states of (85)Rb atoms

We investigate the effects of spontaneously generated coherence (SGC) on the electromagnetically induced transparency features in a four-level Lambda-type system. We show that double-transparency windows and a controllable narrow absorption peak can be obtained with the presence of SGC. We present an equivalent system without the rigorous requirement of close-lying levels to observe the phenomena. We also experimentally demonstrate the corresponding features in a rubidium atomic beam.     

The Perturbation between the G(1)Pi(g) and 2(1)Delta(g) States of (7)Li(2)

We have observed the rotational levels in the v = 2, 3, 5, 6, 7, and 8 vibrational manifolds of the 2(1)Delta(g) state of (7)Li(2) via the A(1)Sigma(+)(u) intermediate levels by DeltaLambda = 2 transitions. This violation of the DeltaLambda = 0, +/-1 selection rule is due to the interaction with the G(1)Pi(g) state. Band-by-band deperturbations of the G(1)Pi(g) approximately 2(1)Delta(g) (v(Pi), v(Delta)) = (11, 2), (12, 3), (15, 5), (16, 6), (18, 7), and (19, 8) bands have been performed. Deperturbed molecular constants and rotational-electronic interaction parameters are reported here. Copyright 2000 Academic Press.     

The 2(3)Delta(g) State of (7)Li(2)

Using pulsed perturbation-facilitated optical-optical double resonance (PFOODR) spectroscopy, the 2(3)Delta(g) state of (7)Li(2) (electronic configuration (varsigma(g)2s) (4ddelta(g)), effective principal quantum number n* = 4.101) has been observed and assigned. Molecular constants and a RKR potential energy curve were obtained. The major molecular constants are Copyright 2000 Academic Press.     

Dissociation energies of the I(3/2g) and I(1/2g) states of Ar+ 2

Rotationally resolved pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectra of ⁴⁰Ar₂ and ³⁶Ar₂ have been recorded between 124650cm^?1 and 127 150cm^?1 following resonant two-photon excitation via the 0⁺ _u (v¹= 0) Rydberg state located below the Ar (¹S₀) + Ar?((3p)⁵4s′ [1/2]₁) dissociation limit. Four overlapping vibrational progressions were observed and attributed to transitions to the I(1/2u) u⁺ = 35–50, I(3/2g) u⁺ = 0–10, I(1/2g) v⁺ = 0–6 and I(3/2u) v⁺ = 0–2 vibronic states of Ar⁺ ₂. The vibrational quantum numbers of the ionic states were derived from an analysis of the isotopic shifts, and the dissociation energies of the I(3/2g) (D⁺ ₀(⁴⁰Ar⁺ ₂:) = 1509.4 ± 1.2cm^?1) and the I(1/2g) (D⁺ ₀(⁴⁰Ar⁺ ₂) = 616.3 ± 1.2cm^?1) states were determined.     

Elastic scattering of electrons by hydrogen atoms in the (2p) state

Conclusion Since our results are the first set of results in this field, their accuracy can be judged when further results through other methods and through experiment are available.The author is grateful to Dr. J. N. Das for his constant help and encouragement in the preparation of this paper. The numerical results reported in this paper have been calculated on the IBM 1130 at Calcutta University.     

Electrical switching and noise spectrum of Si-SiO2 interface defects generated by hot electrons

We observe at low temperatures the noise caused by switching the occupancy of individual interface defect states that have been created during electrical stress with high drain voltages. These results are compared with measurements of traps present in undamaged n-channel Si(100) MOSFETs.     

Strong magnetic instability in correlated metallic Bi(2)Ir(2)O(7)

We report an experimental/theoretical study of single-crystal Bi(2)Ir(2)O(7) that possesses a metallic state with strongly exchange-enhanced paramagnetism. The ground state of Bi(2)Ir(2)O(7) is characterized by the following features: (1) a divergent low-temperature magnetic susceptibility that indicates no long-range order down to 50?mK; (2) strongly field-dependent coefficients of the low-temperature T and T(3) terms of the specific heat; (3) a conspicuously large Wilson ratio R(W)?≈?53.5; and (4) unusual temperature and field dependences of the Hall resistivity that abruptly change below 80?K, without any clear correlation with the magnetic behavior. All these unconventional properties suggest the existence of an exotic ground state in Bi(2)Ir(2)O(7).     

Model-independent analysis of muon g(mu) - 2

We consider possible physics beyond the standard model that could account for the large recently reported [Muon g-2 Collaboration, H. N. Brown et al., Phys. Rev. Lett. 86, 2227 (2001)] effect in g(mu)-2. If the underlying theory can be treated perturbatively, then the only possibilities are models that contain particles that yield "direct" contributions, e.g., supersymmetric models, models with unexpectedly light leptoquarks, or with a rather exotic heavy vector boson. If the underlying theory involves strong interactions, as in technicolor models, then the discrepancy could be accounted for by a variety of mechanisms.     

Dynamics of Pd monomers and dimers adsorbed on the (001) surfaces of strongly correlated nickel oxides

The adsorption and diffusion of Pd monomers and dimers on the (001) surfaces of strongly correlated nickel oxides were investigated using density functional theory combined with the on-site Coulomb repulsion U. The results were compared with those of Pd on nonmagnetic MgO(001). For the Pd monomer, the most stable adsorption site was found to be near the surface O atom. The surface diffusion of the Pd monomer occurred by a hopping process over surface hollow sites. The diffusion energy barrier was 0.21 eV, which was lower than that for Pd on MgO(001). In the case of the Pd dimer, the smallest and stable cluster, the most stable adsorption structure had a flat geometry, with both Pd atoms sitting above the neighboring surface O atoms. The surface diffusion of the Pd dimer occurred by rotational and sliding processes, in contrast to that of the Pd dimer on MgO(001). The diffusion energy barriers ranged from 0.33 to 0.36 eV. The values for the surface diffusion of Pd dimers on NiO(001) were lower than those of Pd on MgO(001). This suggests that Pd dimers move more rapidly on NiO(001) than on MgO(001), and that the sintering of Pd clusters closely related to catalytic activities can occur more easily compared to that of Pd on MgO(001).     

(e,3e) on helium at low impact energy: the strongly correlated three-electron continuum

Double ionization of the helium atom by slow electron impact (E(0)=106 eV) is studied in a kinematically complete experiment. Because of a low excess energy E(exc)=27 eV above the double ionization threshold, a strongly correlated three-electron continuum is realized. This is demonstrated by measuring and calculating the fully differential cross sections for equal energy sharing of the final-state electrons. While the electron emission is dominated by a strong Coulomb repulsion, also signatures of more complex dynamics of the full four-body system are identified.     

Spontaneous symmetry breaking in a system of strongly interacting multicomponent fermions (electrons with spin and conducting nanotubes)

We calculate the ground-state wave functions for a system of multicomponent strongly interacting fermions. We show that it is a state with spontaneously broken chiral symmetry that describes a phase with a finite density of chiral complexes. The number of particles constituting a complex depends on the number of fermion components. For example, in the case of two-component electrons (spin), the condensate is built of four-particle complexes consisting of two “right” electrons and two “left” holes with the opposite spins. The article is published in the original.