Efficiency of three-terminal thermoelectric transport under broken-time reversal symmetry

We investigate thermoelectric efficiency of systems with broken time reversal symmetry under a three-terminal transport. Using a model of Aharonov-Bohm interferometer formed with three noninteracting quantum dots, we show that Carnot efficiency can be achieved when the thermopower is a symmetric function of the applied magnetic field. On the other hand, the maximal value of the efficiency at maximum power is obtained for asymmetric thermopower. Indeed, we show that Curzon-Ahlborn limit is exceeded within the linear response regime in our model. Moreover, we investigate thermoelectric efficiency for random Hamiltonians drawn from the Gaussian Unitary Ensemble and for a more abstract transmission model. In this latter model we find that the efficiency is improved using sharp energy-dependent transmission functions.Comment: 10 pages, 8 figure

Adiabatic Quantum Transport in a Spin Chain with a Moving Potential

Many schemes to realize quantum state transfer in spin chains are not robust to random fluctuations in the spin-spin coupling strength. In efforts to achieve robust quantum state transfer, an adiabatic quantum population transfer scheme is proposed in this study. The proposed scheme makes use of a slowly moving external parabolic potential and is qualitatively explained in terms of the adiabatic following of a quantum state with a moving separatrix structure in the classical phase space of a pendulum analogy. Detailed aspects of our adiabatic population transfer scheme, including its robustness, is studied computationally. Applications of our adiabatic scheme in quantum information transfer are also discussed, with emphasis placed on the usage of a dual spin chain to encode quantum phases. The results should also be useful for the control of electron tunneling in an array of quantum dots.Comment: 10 pages, 10 figures, to appear in Physical Review

Studies of quantum spin chain dynamics and their potential applications in quantum information

Ph.DDOCTOR OF PHILOSOPH

Heat current rectification and mobility edges

We investigate how the presence of a single-particle mobility edge in a system can generate strong heat current rectification. Specifically, we study a quadratic bosonic chain subject to a quasi-periodic potential and coupled at its boundaries to spin baths of differing temperature. We find that rectification increases by orders of magnitude depending on the spatial position in the chain of localized eigenstates above the mobility edge. The largest enhancements occur when the coupling of one bath to the system is dominated by a localized eigenstate, while the other bath couples to numerous delocalized eigenstates. By tuning the parameters of the quasi-periodic potential it is thus possible to vary the amplitude, and even invert the direction, of the rectification.Comment: 5+3 pages 4+4 figure

A clinical study of cutaneous changes in pregnancy

AbstractBackground/objectivePregnant women experience a myriad of physiological and metabolic changes that affect different organ systems in the body. Cutaneous and appendageal alterations that manifest during pregnancy are largely modulated by hormonal, immunologic, and metabolic factors. Detailed reports encompassing physiological changes and specific dermatoses of pregnancy and effects of various dermatoses on pregnant women are scanty in literature. This study was conducted to examine in detail both physiological changes and specific dermatoses. The cutaneous changes are divided into physiological changes, skin diseases aggravated by pregnancy, and specific dermatoses of pregnancy. The objectives were to study the various cutaneous changes of pregnancy and to know the proportion of these cutaneous manifestations in pregnant women.MethodsThis study included 600 pregnant women attending the Obstetrics and Gynecology Department of a tertiary teaching hospital in Northern Kerala, India. Detailed history elicitation and complete physical and dermatological examination were performed. Skin biopsy was performed in relevant cases.ResultsCutaneous changes were seen in a majority of patients, of which physiological changes were the most common (99%). The most common cutaneous manifestation was hyperpigmentation (526; 87.6%), followed by striae gravidarum (72.8%). Other changes were vascular, including pedal edema (10%), pregnancy gingivitis (1.8%), and varicose veins (1%). Infections were the common dermatological problem in this study group. The most common infections were vulvovaginal candidiasis (21%), Tinea versicolor (6%), scabies (2.8%), dermatophytosis (1.5%), and sexually transmitted infection (0.5%). Specific dermatoses were seen in 12 cases (2%), with the most common being pruritic urticarial papules and plaques of pregnancy (1.3%).ConclusionPregnant women are prone to suffer from a wide range of dermatological problems apart from specific dermatoses of pregnancy. The study emphasizes the need for a detailed and meticulous examination of these patients to detect these various disorders

Slow relaxation of out-of-time-ordered correlators in interacting integrable and nonintegrable spin-1/2 XYZ chains

Out-of-time ordered correlators (OTOCs) help characterize the scrambling of quantum information and are usually studied in the context of nonintegrable systems. In this work, we compare the relaxation dynamics of OTOCs in interacting integrable and nonintegrable spin-1/2 XYZ chains in regimes without a classical counterpart. In both kinds of chains, using the presence of symmetries such as $U(1)$ and supersymmetry, we consider regimes in which the OTOC operators overlap or not with the Hamiltonian. We show that the relaxation of the OTOCs is slow (fast) when there is (there is not) an overlap, independently of whether the chain is integrable or nonintegrable. When slow, we show that the OTOC dynamics follows closely that of the two-point correlators. We study the dynamics of OTOCs using numerical calculations, and gain analytical insights from the properties of the diagonal and of the off-diagonal matrix elements of the corresponding local operators in the energy eigenbasis.Comment: 11 pages, 4 figures, as publishe