Dharma-wardana replies

Dharma‐wardana, M. W. C.

doi:10.1103/physrevlett.67.2917

Cited by 110 publications

(290 citation statements)

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“…The enhancement of m * g * in the 1-valley 2DES of GaAs/AlAs systems is found to be strongly dependent on the spin polarization [5], in strong contrast to the Si-MOSFET case. Our calculations [3] show that the physics of the 1-valley system is dominated by the presence of a transition to a fully polarized state which makes g * increase rapidly with r s as the transition density is approached. The 2-valley system shows no such transition to the spinpolarized state and is insensitive to the spin polarization.…”

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confidence: 93%

“…In a recent study of the effective mass m * and the effective Landé-g factor of the 2DES, the Coulomb coupling between the electrons of the two valleys was shown to have a dramatic effect at low densities when the coupling becomes large [3]. In effect, the elementary excitations of the two fluids in the two valleys interact to form coupled modes, giving rise to new effects.…”

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confidence: 99%

“…It was shown experimentally [4] that m * g * rises rapidly with decreasing density in Si-MOSFETS, and that this rise is due to a dramatic increase in m * , independent of the spin polarization, while g * remains essentially constant. Calculations for the Si system which account for the inter-valley Coulomb coupling quantitatively predict [3] the sharp increase in m * g * . It was also shown that g * remained essentially constant, in strong contrast to the behaviour found for the simple one valley 2DES [3].…”

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confidence: 99%

“…Calculations for the Si system which account for the inter-valley Coulomb coupling quantitatively predict [3] the sharp increase in m * g * . It was also shown that g * remained essentially constant, in strong contrast to the behaviour found for the simple one valley 2DES [3]. The effective mass was also shown to be practically independent of the spin polarization ζ, in excellent quantitative agreement with the data of of Shashkin et al [4] for Si-MOSFETS.…”

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Spin- and valley-dependent analysis of the two-dimensional low-density electron system in Si MOSFETs

Dharma‐wardana

Perrot

2004

Phys. Rev. B

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The 2-D electron system (2DES) in Si metal-oxide field-effect transistors (MOSFETS) consists of two distinct electron fluids interacting with each other. We calculate the total energy as a function of the density n, and the spin polarization ζ in the strongly-correlated low-density regime, using a classical mapping to a hypernetted-chain (CHNC) equation inclusive of bridge terms. Here the ten distribution functions, arising from spin and valley indices, are self-consistently calculated to obtain the total free energy, the chemical potential, the compressibility and the spin susceptibility. The T = 0 results are compared with the 2-valley Quantum Monte Carlo (QMC) data of Conti et al.(at T = 0, ζ = 0) and found to be in excellent agreement. However, unlike in the one-valley 2DES, it is shown that the unpolarized phase is always the stable phase in the 2-valley system, right up to Wigner Crystallization at rs = 42. This leads to the insensitivity of g * to the spin polarization and to the density. The compressibility and the spin-susceptibility enhancement calculated from the free energy confirm the validity of a simple approach to the two-valley response based on coupledmode formation. This enables the use of the usual (single-valley) exchange-correlation functionals in quantum calculations of MOSFET properties provided mode-coupling effects are taken into account. The enhancement of the spin susceptibilty calculated from the coupled-valley response and directly from the 2-valley energies is discussed. The three methods, QMC, CHNC, and Coupled-mode theory agree closely. Our results contain no ad hoc fit parameters. They agree with experiments and do not invoke impurity effects or metal-insulator transition phenomenology.

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confidence: 93%

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confidence: 99%

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confidence: 99%

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Spin- and valley-dependent analysis of the two-dimensional low-density electron system in Si MOSFETs

Dharma‐wardana

Perrot

2004

Phys. Rev. B

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“…Dharmawardana in a series of papers [21] has calculated the effective mass, Landé g * -factor and spin susceptibility for Q2D electron systems within the classical-map hypernetted chain (CHNC) approximation. He found that the thickness effect on the spin-phase transition provides a clear picture of the changes in the spin susceptibility enhancement leading to a strong increase in the g * -factor, while the effective mass is increased from the reduction of the Coulomb potential in thick layers.…”

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confidence: 99%

Quasi-particle properties in a quasi-two-dimensional electron liquid

Asgari

Tanatar

2008

Pramana - J Phys

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Abstract.We consider the quasi-particle properties such as the effective mass and spin susceptibility of quasi-two-dimensional electron systems. The finite quantum well width effects are incorporated into the local-field factors that describe the charge and spin correlations. We employ the Fermi-hypernetted chain formalism in conjunction with fluctuationdissipation theorem to obtain the local-field factors. Our results are in good agreement with recent experiments.

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Chronic Kidney Disease of Unknown Etiology (CKDu) – The Search for Causes and the Impact of Its Politicization

Dharma‐wardana¹

2023

Medical Geology

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Kidney disease of unknown aetiology (CKDu) has been identified in many countries extending from MesoAmerica and Egypt, to South-east Asia and China. Although CKDu has been linked by various authors to farming, it is an artifact of treating multi-modal disease distributions as unimodal. There is NO correlation of CKDu with agriculture since affected farming villages are often surrounded by other farming villages free of CKDu. Initial studies looked for a correlation of CKDu with toxic heavy metal residues of arsenic, cadmium etc., or herbicides like glyphosate that may be present in the environment, as the causative factors. There is now considerable consensus that their concentrations are below danger thresholds, be it in Mesoamerica or south-east Asia. The conceptual basis of a search for etiology within a systems approach is discussed, and attempts to name the disease to bias the identification of its etiology are reviewed. Current research has narrowed down the etiology to geochemical electrolytic contaminants like fluorides and ionic components in hard water, nanosilica (found in water as well as in the air), as well as renal toxins similar to indoxyl sulphates that may arise from interactions of ions with humic acids contained in aqueous organic matter. However, while agrochemical toxins are increasingly considered less relevant to the etiology of CKDu, it has become a firm public belief. In Sri Lanka this has spawned ideology-based agricultural policies for partial and complete banning of agrochemicals (2014-2021), followed by some back-tracking, disrupting the economy and the food supply. A farmer's uprising in 2022 was spawned by poor harvests. It triggered a larger popular uprising that led to the collapse of a government wedded to romanticized eco-extremist agricultural policies in a country already facing difficulties in the wake of Covid and Ukraine.

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Dharma-wardana replies

Cited by 110 publications

References 3 publications

Spin- and valley-dependent analysis of the two-dimensional low-density electron system in Si MOSFETs

Spin- and valley-dependent analysis of the two-dimensional low-density electron system in Si MOSFETs

Quasi-particle properties in a quasi-two-dimensional electron liquid

Chronic Kidney Disease of Unknown Etiology (CKDu) – The Search for Causes and the Impact of Its Politicization

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