Strange Half Metals and Mott Insulators in SYK Models

We study a dual flavor fermion model where each of the flavors form a Sachdev-Ye-Kitaev (SYK) system with arbitrary and possibly distinct $q$-body interactions. The crucial new element is an arbitrary all-to-all $r$-body interaction between the two flavors. At high temperatures the model shows a strange metal phase where both flavors are gapless, similar to the usual single flavor SYK model. Upon reducing temperature, the coupled system undergoes phase transitions to previously unseen phases - first, a strange half metal (SHM) phase where one flavor remains a strange metal while the other is gapped, and, second, a Mott insulating phase where both flavors are gapped. At a fixed low temperature we obtain transitions between these phases by tuning the relative fraction of sites for each flavor. We discuss the physics of these phases and the nature of transitions between them. This work provides an example of an instability of the strange metal with potential to provide new routes to study strongly correlated systems through the rich physics contained in SYK like models.Comment: 7 pages, 3 figure

Magnetic and the magnetocaloric properties of Ce1-xRxFe2 and Ce(Fe1-xMx)2 compounds

We have studied selected rare earth doped and transition metal doped CeFe2 compounds by examining their structural, magnetic and magneto-thermal properties. With substitution of Ce by 5 and 10% Gd and 10% Ho, the Curie temperature can be tuned to the range of 267-318 K. Localization of Ce 4f electronic state with rare earth substitutions is attributed for the enhancement of Curie temperature. On the other hand, with Ga and Al substitution at the Fe site, system undergoes paramagnetic to ferromagnetic transition and then to an antiferromagnetic phase on cooling. The magnetocaloric effect across the transitions has been studied from both magnetization isotherms and heat capacity data. It is shown that by choosing the appropriate dopant and its concentration, the magnetocaloric effect around room temperature can be tuned.Comment: 13 pages, 6 figures, 2 table

Ultrasonic pulse induced mechanoluminescence of europium doped strontium aluminate micro-crystals

When rare earth doped strontium aluminate micro-crystals are exposed to ultrasonic pulse, then mechanumnescence (ML) is induced. The intensity of ML is proportional to the power of ultrasonic pulse used for ML excitation. The ML in europium doped strontium aluminate micro-crystals can be understood on the basis of the piezoelectrically induced electron detrapping model. On the basis of the piezoelectrically-induced electron detrapping model, expressions are derived for the general kinetics of ML intensity, rise of ML intensity, peak ML intensity and decay of ML intensity, in which good agreement is found between the theoretical and experimental results. A linear relation between the ML intensity and the ultrasonic power can also be understood on the basis of the proposed theory. The present investigation shows that the ML can be used to detecting the presence of ultrasonic waves and also for the measurement of ultrasonic power.&nbsp

Energy level statistics of interacting trapped bosons

It is an well established fact that statistical properties of energy level spectra are the most efficient tool to characterize nonintegrable quantum systems. The study of statistical properties and spectral fluctuation in the interacting many boson systems have developed a new interest in this direction. Specially we are interested in the weakly interacting trapped bosons in the context of Bose-Einstein condensation (BEC) as the energy spectrum shows a transition from the collective to single particle nature with the increase in the number of levels. However this has received less attention as it is believed that the system may exhibit Poisson like fluctuations due to the existence of external harmonic trap. Here we compute numerically the energy levels of the zero-temperature many-boson systems which are weakly interacting through the van der Waals potential and are in the 3D confined harmonic potential. We study the nearest neighbour spacing distribution and the spectral rigidity by unfolding the spectrum. It is found that increase in number of energy levels for repulsive BEC induces a transition from a Wigner like form displaying level repulsion to Poisson distribution for P(s). It does not follow the GOE prediction. For repulsive interaction, the lower levels are correlated and manifest level repulsion. For intermediate levels P (s) shows mixed statistic which clearly signifies the existence of two energy scales: external trap and interatomic interaction. Whereas for very high levels the trapping potential dominates, genarating Poisson distribution. Comparison with mean-field results for lower levels are also presented. For attractive BEC near the critical point we observe the Shrielman like peak near s=0 which signifies the presence of large number of quasi-degenerate states.Comment: 12 page

Preclinical evaluation of antihyperglycemic activity of Clerodendron infortunatum leaf against streptozotocin-induced diabetic rats

© The Author(s) 2011. This article is published with open access at Springerlink.com Introduction: Clerodendron infortunatum Linn. (Verbenaceae), commonly known as Bhant in Hindi, is a small shrub occurring throughout the plains of India, which is traditionally used for several medicinal purposes. The aim of the present stud