Superconductivity in Nanostructured Ga-Ag Eutectic Alloy

The dc and ac magnetizations were studied for the eutectic Ga-Ag alloy embedded into a porous glass with 7 nm mean pore size. The measurements were performed within a temperature range of 1.9 to 10 K which covers the superconducting transition for the nanocomposite. The onset of superconductivity at the magnetic field 10 Oe was found at about 7.1 K which is much higher than in bulk gallium. The phase diagram showed a positive curvature at low magnetic fields. The activation energy of vortex mobility was calculated at different magnetic fields using the ac data.     Keywords: Ga-Ag eutectic alloy, superconductivity, nanoconfinemen

Order parameter configurations in the Lifshitz-type incommensurate ferroelectric thin films

The Dzialoshinskii model of periodic and helicoidal structures has been analyzed without neglecting of the amplitude function oscillations. The amplitude function oscillations are shown to be important for understanding of the nature of the phase function. Analytic consideration is carried out in the limit of small anisotropy (neglecting the cosine term in the Hamiltonian). Surprisingly, the phase jumps survive even in the limit of the vanishing anisotropy

Magnetic Properties of Topological Insulators Bi2-xCrxSe3 WITH x=0.1, 0.3 and 0.6

In this work, we have studied magnetic properties of Bi2-xCrxSe3 single crystals with x=0.1, 0.3 и 0.6. The homogeneous distribution of dopants was justified by the energy-dispersive X-ray spectroscopy. Different types of magnetic phase transitions were observed in samples with various compositions.Исследования проводились с использованием оборудования Ресурсных центров Научного парка СПбГУ. Работа поддержана РНФ, грант 21-72-20038

125Te spin-lattice relaxation in a candidate to Weyl semimetals WTe2

The tungsten ditelluride WTe2 was suggested to belong to the Weyl semimetal family. We studied 125Te spin-lattice relaxation and NMR spectra in a WTe2 single crystal within a large range from 28 K up to room temperature. Measurements were carried out on a Bruker Avance 500 NMR pulse spectrometer for the crystalline c axis directed in parallel and perpendicular to the magnetic field. Relaxation proved to be single-exponential. The relaxation time varied depending on the sample position in magnetic field and frequency offset. The relaxation rate increased about linearly with temperature below 70 K, however the dependence became nearly quadratic at higher temperatures. The relaxation rate within the total temperature range was fitted using a theoretical model developed in Ref. [41] for Weyl semimetals and assuming the decrease of the chemical potential with increasing temperature. The results obtained for 125Te spin-lattice relaxation evidence in favor of the topological nontriviality of the WTe2 semimetal. The 125Te NMR spectra agreed with the occurrence of nonequivalent tellurium sites and varied insignificantly with temperature. © 2020 The Author(s)The authors acknowledge the financial support from RFBR , grants 19-57-52001 , 19-29-03004 , and 19-07-00028 . The work was partly supported by Minobrnauki of Russia (“Spin” No. AAAA-A18-118020290104-2 ) and Russian Government (contract No. 02.A03.21.0006 ). Measurements were partly carried out using the equipment of the Research park of St. Petersburg State University