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Luttinger liquid behavior in tunneling through a quantum dot at zero magnetic field  [PDF]
Paula Rojt,Yigal Meir,Assa Auerbach
Physics , 2002, DOI: 10.1103/PhysRevLett.89.256401
Abstract: Thermodynamic and transport properties of a two dimensional circular quantum dot are studied theoretically at zero magnetic field. In the limit of a large confining potential, where the dot spectrum exhibits a shell structure, it is argued that both spectral and transport properties should exhibit Luttinger liquid behavior. These predictions are verified by direct numerical diagonalization. The experimental implications of such Luttinger liquid characteristics are discussed.
Experimental Evidence for Coulomb Charging Effects in an Open Quantum Dot at Zero Magnetic Field  [PDF]
C. -T. Liang,M. Y. Simmons,C. G. Smith,G. H. Kim,D. A. Ritchie,M. Pepper
Physics , 1998, DOI: 10.1103/PhysRevLett.81.3507
Abstract: We have measured the low-temperature transport properties of an open quantum dot formed in a clean one-dimensional channel. For the first time, at zero magnetic field, continuous and periodic oscillations superimposed upon ballistic conductance steps are observed when the conductance through the dot $G$ exceeds $2e^2/h$. We ascribe the observed conductance oscillations to evidence for Coulomb charging effects in an open dot. This is supported by the evolution of the oscillating features for $G>2e^2/h$ as a function of both temperature and barrier transparency. Our results strongly suggest that at zero magnetic field, current theoretical and experimental understanding of Coulomb charging effects overlooks charging in the presence of fully transmitted 1D channels.
The Hanle Effect as a Magnetic Diagnostic  [PDF]
Richard Ignace
Physics , 2003,
Abstract: The physics of the Hanle effect is briefly reviewed, and its application as a diagnostic of hot star magnetic fields is described. Emphasis is given to the practicalities of using spectropolarimetry of resolved wind emission lines to infer information about the circumstellar magnetic field strength and its geometry. A model for a weakly magnetized wind from "WCFields" theory is used as the backdrop for investigating polarized line profile effects for P Cygni resonance lines using a kind of "last scattering approximation". Model results are presented for a typical P Cygni line that forms in a spherical wind. Significant line polarizations of a few tenths of a percent can result for circumstellar fields of order 100G. Information about the field topology and surface field strength is gleaned from the Stokes-Q and U-profiles. Simplistically, the Q-profile polarization is governed by the field strength, and the U-profile symmetry (whether symmetric or anti-symmetric or even zero) is governed by the field geometry.
Quantum-dot lithium in zero magnetic field: Electronic properties, thermodynamics, and a liquid-solid transition in the ground state  [PDF]
S. A. Mikhailov
Physics , 2001, DOI: 10.1103/PhysRevB.65.115312
Abstract: Energy spectra, electron densities, pair correlation functions and heat capacity of a quantum-dot lithium in zero external magnetic field (a system of three interacting two-dimensional electrons in a parabolic confinement potential) are studied using the exact diagonalization approach. A particular attention is given to a Fermi-liquid -- Wigner-solid transition in the ground state of the dot, induced by the intra-dot Coulomb interaction.
Temperature dependence of electron-spin relaxation in a single InAs quantum dot at zero applied magnetic field  [PDF]
X. M. Dou,B. Q. Sun,D. S. Jiang,H. Q. Ni,Z. C. Niu
Physics , 2012, DOI: 10.1063/1.3692066
Abstract: The temperature-dependent electron spin relaxation of positively charged excitons in a single InAs quantum dot (QD) was measured by time-resolved photoluminescence spectroscopy at zero applied magnetic fields. The experimental results show that the electron-spin relaxation is clearly divided into two different temperature regimes: (i) T < 50 K, spin relaxation depends on the dynamical nuclear spin polarization (DNSP) and is approximately temperature-independent, as predicted by Merkulov et al. (ii) T > about 50 K, spin relaxation speeds up with increasing temperature. A model of two LO phonon scattering process coupled with hyperfine interaction is proposed to account for the accelerated electron spin relaxation at higher temperatures.
Hanle Effect in Transport through Quantum Dots Coupled to Ferromagnetic Leads  [PDF]
Matthias Braun,Jürgen K?nig,Jan Martinek
Physics , 2004, DOI: 10.1209/epl/i2005-10230-0
Abstract: We suggest a series of transport experiments on spin precession in quantum dots coupled to one or two ferromagnetic leads. Dot spin states are created by spin injection and analyzed via the linear conductance through the dot, while an applied magnetic field gives rise to the Hanle effect. Such a Hanle experiment can be used to determine the spin lifetime in the quantum dot, to measure the spin injection efficiency into the dot, as well as proving the existence of intrinsic spin precession which is driven by the Coulomb interaction.
Photospheric Hanle diagnostic of weak magnetic dipoles in stars  [PDF]
A. López Ariste,A. Asensio Ramos,C. González Fernández
Physics , 2010, DOI: 10.1051/0004-6361/201015388
Abstract: Diagnostic techniques for stellar magnetic fields based upon spectropolarimetry. We propose and explore a new technique based upon the linear polarization emitted in Hanle-sensitive lines in disk-integrated stars where a dipolar magnetic field breaks the rotational symmetry of the resonance scattering polarization. A star with a simple dipolar field and a 1-0 spectral line are used to compute polarization amplitudes and angles.Predicted amplitudes are low but within reach of present instruments. A new application of the Hanle effect is proposed and analyzed, a tool that allows measuring of some of the weakest stellar magnetic fields.
Inhomogeneous chiral condensates and non-analyticity under an external magnetic field  [PDF]
Kouji Kashiwa,Tong-Gyu Lee,Kazuya Nishiyama,Ryo Yoshiike
Physics , 2015,
Abstract: We investigate inhomogeneous chiral condensates, such as the so-called dual chiral density wave of dense quark matter, under an external magnetic field at finite real and imaginary chemical potentials. In a model-independent manner, we find that analytic continuation from imaginary to real chemical potential is not possible due to the singularity induced by inhomogeneous chiral condensates at zero chemical potential. From the discussion on the non-analyticity and methods used in lattice QCD simulations, e.g., Taylor expansion, and the analytic continuation with an imaginary chemical potential, it turns out that information on an inhomogeneous chiral condensed phase is missed in the lattice simulations at finite baryon chemical potentials unless the non-analyticity at zero chemical potential is correctly considered. We also discuss an exceptional case without such non-analyticity at zero chemical potential.
Anomalous Kondo-effect in Quantum Dot at non-zero bias  [PDF]
F. Simmel,R. H. Blick,J. P. Kotthaus,W. Wegscheider,M. Bichler
Physics , 1998, DOI: 10.1103/PhysRevLett.83.804
Abstract: We present measurements on the Kondo-effect in a small quantum dot connected strongly to one lead and weakly to the other. The conductance of the dot reveals an offset of the Kondo resonance at zero magnetic field. While the resonance persists in the negative bias regime, it is suppressed in the opposite direction. This demonstrates the pinning of the Kondo resonance to the Fermi levels of the left and right lead. As an outlook we exploit the spin blockade effect to gain information about the spin state of the quantum dot in the Kondo regime.
Magnetic Freezing Effect for the Ground State of Quantum Dot  [PDF]
V. D. Krevchik,A. B. Grunin,A. K. Aringazin,M. B. Semenov
Physics , 2002,
Abstract: Within the framework of zero-range potential model in the ap-proach of effective mass, the impurity absorption by the complex Quantum Dot-Impurity Center in an external constant uniform magnetic field is considered. Under condition that the influence of a magnetic field on the ground state of quantum dot is negligible, we have derived the light absorption coefficient of impurity for the case of longitudinal polarization. It is shown that with an increase of the intensity of magnetic field the threshold of an impurity absorption band is shifted to the short-wave spectrum region. Also, the absorption coefficient increases by several times that can be explained as a result of the "magnetic freezing" effect for the ground state of quantum dot.
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