We report the first experimental observation of superconductivity in Cd3As2 thin films without application of external pressure. Surface studies suggest that the observed transport characteristics are related to the polycrystalline continuous part of investigated films with homogeneous distribution of elements and the Cd-to-As ratio close to stoichiometric Cd3As2. The latter is also supported by Raman spectra of the studied films, which are similar to those of Cd3As2 single crystals. The formation of superconducting phase in films under study is confirmed by the characteristic behavior of temperature and magnetic field dependence of samples resistances, as well as by the presence of pronounced zero-resistance plateaux in dV /dI characteristics. The corresponding Hc−Tc plots reveal a clearly pronounced linear behavior within the intermediate temperature range, similar to that observed for bulk Cd3As2 and Bi2Se3 films under pressure, suggesting the possibility of nontrivial pairing in the films under investigation. We discuss a possible role of sample inhomogeneities and crystal strains in the observed phenomena.Weyl and Dirac semimetals (WSM and DSM) currently attract wide interest related to the existence of Dirac nodes in their electron spectrum and related nontrivial topological characteristics of both bulk and surface states [1][2][3]. A special attention is drawn to the Cd 3 As 2 compound, which proved to be air-stable, unlike some other DSM materials [4][5][6][7][8]. This compound is known and has been studied for quite a long time [9][10][11][12]. Nevertheless, it is still very popular since the Dirac nodes of this semimetal are protected by the crystal symmetry and the electron states exhibit interesting topological properties, such as spin-momentum locking. Due to the high symmetry, DSM materials can undergo transitions to other topological phases (e.g. WSM) as a result of breaking certain symmetries or applying some external factors.The existence of topologically protected electron states gives a new impetus to the problem of topological superconductivity (TSC) being discussed for a long time [13][14][15]. In particular, Refs. [16,17] provide a theoretical analysis of the possible types of SC pairing in the systems of Cd 3 As 2 type, including topologically nontrivial ones. Basically, the existence of nontrivial pairing potential (leading to the emergence of triplet Cooper pairs) should induce the formation of Majoranna modes at the surface of the crystal, which can be used in the faulttolerant quantum computing [14]. The SC phase emergence in Cd 3 As 2 was reported in Ref.[18], however, it was observed at pressures above the structural transition from the tetragonal to trigonal phase. While theoretical works suggest the stabilization of TSC phase upon such symmetry lowering [16,17], such transition also implies appearance of the gap at Dirac nodes, thus, suppressing the DSM phase. Additional indications of the SC phase in Cd 3 As 2 were also observed in the point-contact spectroscopy experiments and att...

We study how the non-Fermi-liquid two-phase state reveals itself in transport properties of highmobility Si-MOSFETs. We have found features in zero-field transport, magnetotransport, and thermodynamic spin magnetization in a 2D correlated electron system that may be directly related with the two-phase state. The features manifest above a density dependent temperature T * that represents a novel high-energy scale, apart from the Fermi energy. More specifically, in magnetoconductivity, we found a sharp onset of the novel regime δσ(B, T ) ∝ (B/T ) 2 above a density-dependent temperature T kink (n), a high-energy behavior that "mimics" the low-temperature diffusive interaction regime. The zero-field resistivity temperature dependence exhibits an inflection point T infl (n). In thermodynamic magnetization, the weak-field spin susceptibility per electron, ∂χ/∂n changes sign at T dM/dn (n). All three notable temperatures, T kink , T infl , and T dM/dn , behave critically ∝ (n − nc), are close to each other, and are intrinsic to high-mobility samples solely; we therefore associate them with an energy scale T * caused by interactions in the 2DE system. [5][6][7], metal-insulator transition (MIT) [1,5,[8][9][10], strong positive magnetoresistance (MR) in parallel field [11][12][13][14][15][16][17][18], strong renormalization of the effective mass and spin susceptibility [2,[19][20][21][22][23][24], etc.Far away from the critical MIT density n c , in the well "metallic regime," these effects are explained within the framework of the Fermi liquid theory -either in terms of interaction quantum corrections (IC) [25,26], or temperaturedependent screening of the disorder potential [27][28][29][30][31]. Both theoretical approaches so far are used to treat the experimental data on transport, and the former one -also to determine the Fermi liquid coupling constants from fitting the transport and magnetotransport data to the IC theory. In the close vicinity of the critical region, conduction is treated within the renormalization group [32][33][34][35][36], or the Wigner-Mott approach [37,38].On the other side, a number of theories predicts breakdown of the uniform paramagnetic 2D Fermi liquid state due to instability in the spin or charge channel, developing as interaction strength increases [39][40][41][42][43]. However, how the potential instabilities reveal themselves in charge transport remains an almost unexplored question.On the spin polarization of the 2D electron system Spin fluctuations are believed to play an important role in the 2DE system, especially near the apparent metalinsulator transition. Ferromagnetic instabilities result from the interplay of the electronic interactions and the Pauli principle. The interaction energy can be minimized when the fermion antisymmetry requirement is satisfied by the spatial wave function resulting in the alignment of spins and a large ground-state spin magnetization. In clean metals, the long-range part of the Coulomb interaction is screened, whereas its short-range part leads to s...

We study diffusive electron-electron interaction correction to conductivity by analyzing simultaneously ρxx and ρxy for disordered 2D electron systems in Si in tilted magnetic field. Tilting the field is shown to be a straightforward tool to disentangle spin and orbital effects. In particular, by changing the tilt angle we prove experimentally that in the field range gµBB > kBT the correction depends on modulus of magnetic field rather than on its direction, which is expected for a system with isotropic g-factor. In the high-field limit the correction behaves as ln(B), as expected theoretically (Lee, Ramakrishnan, Phys. Rev. B26 , 4009 (1982)). Our data prove that the diffusive electron-electron interaction correction to conductivity is not solely responsible for the huge and temperature dependent magnetoresistance in parallel field, typically observed in Si-MOSFETs.

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