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Electronic thermoelectric power factor and metal-insulator transition in FeSb2 Authors:Qing Jie, Rongwei Hu, Emil Bozin, A. Llobet, I. Zaliznyak, C. Petrovic, Q. Li (Submitted on 11 Oct 2012) Abstract: We show that synthesis-induced Metal -Insulator transition (MIT) for electronic transport along the orthorombic c axis of FeSb$_{2}$ single crystals has greatly enhanced electrical conductivity while keeping the thermopower at a relatively high level. By this means, the thermoelectric power factor is enhanced to a new record high S$^{2}$$\sigma$ $\sim$ 8000 $\mu$WK$^{-2}$cm$^{-1}$ at 28 K. We find that the large thermopower in FeSb$_{2}$ can be rationalized within the correlated electron model with two bands having large quasiparaticle disparity, whereas MIT is induced by subtle structural differences. The results in this work testify that correlated electrons can produce extreme power factor values. Comments: 7 pages, 6 figures Subjects: Strongly Correlated Electrons (cond-mat.str-el); Materials Science (cond-mat.mtrl-sci) Journal reference: Phys. Rev. B 86, 115121 (2012) DOI: 10.1103/PhysRevB.86.115121 Cite as: arXiv:1210.3355 [cond-mat.str-el] (or arXiv:1210.3355v1 [cond-mat.str-el] for this version) Pseudogap state from quantum criticality Authors:K. B. Efetov, H. Meier, C. Pépin (Submitted on 11 Oct 2012) Abstract: Upon application of an external tuning parameter, a magnetic state can be driven to a normal metal state at zero temperature. This phenomenon is known as quantum criticality and leads to fascinating responses in thermodynamics and transport of the compound. In the standard picture, a single quantum critical point occurs at zero temperature, which results in a nontrivial critical behaviour in its vicinity. Here we show that in two dimensions the scenario is considerably more complex due to the enormous amount of quantum fluctuations. Instead of the single point separating the antiferromagnet from the normal metal, we have discovered a broad region between these two phases where the magnetic order is destroyed but certain areas of the Fermi surface are closed by a large gap. This gap reflects the formation of a novel quantum state characterised by a superposition of d-wave superconductivity and a quadrupole-density wave, id est a state in which an electron quadrupole density spatially oscillates with a period drastically different from the one of the original spin-density wave. At moderate temperatures both orders co-exist at short distances but thermal fluctuations destroy the long-range order. Below a critical temperature the fluctuations are less essential and superconductivity becomes stable. This new phenomenon may shed some light on the origin of the mysterious pseudogap state and of the high-temperature transition into the superconducting state in cuprates. Our results demonstrate that quantum phase transitions between antiferromagnets and normal metals in layered materials may be the proper playground for search of new high temperature superconductors. Comments: 32 pages, 12 figures Subjects: Strongly Correlated Electrons (cond-mat.str-el); Superconductivity (cond-mat.supr-con) Cite as: arXiv:1210.3276 [cond-mat.str-el] (or arXiv:1210.3276v1 [cond-mat.str-el] for this version) Field-induced magnetic behavior in quasione-dimensional Ising-like antiferromagnet BaCo2V2O8: a detailed single-crystal neutron diffraction study Authors:E. Canévet, B. Grenier, M. Klanjšek, C. Berthier, M. Horvatić, V. Simonet, P. Lejay (Submitted on 11 Oct 2012) Abstract: BaCo2V2O8 is a nice example of a quasi-one-dimensional quantum spin system that can be described in terms of Tomonaga-Luttinger liquid physics. This is explored in the present study where the magnetic field-temperature phase diagram is thoroughly established up to 12 T using single-crystal neutron diffraction. The transition from the N\'eel phase to the incommensurate longitudinal spin density wave (LSDW) phase through a first-order transition, as well as the critical exponents associated with the paramagnetic to ordered phase transitions, and the magnetic order both in the N\'eel and in the LSDW phase are determined, thus providing a stringent test for the theory. Comments: 16 pages with 15 figures Subjects: Strongly Correlated Electrons (cond-mat.str-el) Cite as: arXiv:1210.3253 [cond-mat.str-el] (or arXiv:1210.3253v1 [cond-mat.str-el] for this version) Signatures of topological phase transitions in mesoscopic superconducting rings Authors:Falko Pientka, Alessandro Romito, Mathias Duckheim, Yuval Oreg, Felix von Oppen (Submitted on 11 Oct 2012) Abstract: We investigate Josephson currents in mesoscopic rings with a weak link which are in or near a topological superconducting phase. As a paradigmatic example, we consider the Kitaev model of a spinless p-wave superconductor in one dimension, emphasizing how this model emerges from more realistic settings based on semiconductor nanowires. We show that the flux periodicity of the Josephson current provides signatures of the topological phase transition and the emergence of Majorana fermions situated on both sides of the weak link even when fermion parity is not a good quantum number. In large rings, the Majorana fermions hybridize only across the weak link. In this case, the Josephson current is h/e periodic in the flux threading the loop when fermion parity is a good quantum number but reverts to the more conventional h/2e periodicity in the presence of fermion-parity changing relaxation processes. In mesoscopic rings, the Majorana fermions also hybridize through their overlap in the interior of the superconducting ring. We find that in the topological superconducting phase, this gives rise to an h/e-periodic contribution even when fermion parity is not conserved and that this contribution exhibits a peak near the topological phase transition. This signature of the topological phase transition is robust to the effects of disorder. As a byproduct, we find that close to the topological phase transition, disorder drives the system deeper into the topological phase. This is in stark contrast to the known behavior far from the phase transition, where disorder tends to suppress the topological phase. Comments: 14 pages, 16 figures Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall) Cite as: arXiv:1210.3237 [cond-mat.mes-hall] (or arXiv:1210.3237v1 [cond-mat.mes-hall] for this version) Emergent Supersymmetric Many-Body Systems in Doped Z2 Topological Spin Liquid of the Toric-Code Model Authors:Jing He, Jing Yu, Xing-Hai Zhang, Su-Peng Kou (Submitted on 11 Oct 2012) Abstract: In this paper, we studied the doped Z2 topological spin liquid of the toric-code model. We found that the doped holes become supersymmetric particles. The ground state of the doped Z2 topological spin liquid becomes new matters of quantum states - supersymmetric Bose-Einstein condensation or supersymmetric superfluid. As a result, this system provides a unique example of manipulatable supersymmetric many-body system. Comments: 4.5 pages, 3 figures Subjects: Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph) Cite as: arXiv:1210.3232 [cond-mat.str-el] (or arXiv:1210.3232v1 [cond-mat.str-el] for this version) Spin Hall Effect Authors:M.I. Dyakonov (Submitted on 11 Oct 2012) Abstract: This is a brief review of the phenomenology of the spin Hall effect and related phenomena. Comments: 12 pages, 4 figures Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Atomic Physics (physics.atomph); Quantum Physics (quant-ph) Journal reference: Future Trends in Microelectronics, S. Luryi, J. Xu, and A. Zaslavsky (eds), Wiley 2010, p. 251 Cite as: arXiv:1210.3200 [cond-mat.mes-hall] (or arXiv:1210.3200v1 [cond-mat.mes-hall] for this version) Sweeping reciprocal vortex lattice across the Fermi surface: A new magnetoquantum oscillations effect in the superconducting state Authors:T. Maniv, V. Zhuravlev (Submitted on 11 Oct 2012) Abstract: It is shown that coherent scatterings by an ordered vortex lattice are critically enhanced for quasi particles moving in cyclotron orbits on the Fermi surface through vortex core regions, thus generating significant quasi-periodic oscillating contributions to the SC free energy as a function of the inverse magnetic field. The mean frequency of the oscillation provides a fingerprint of the vortex lattice geometry. Vortex-lattice disorder, tends to suppress this oscillatory component. Comments: 4 pages, 2 figures, presented on RHMF12 Subjects: Superconductivity (cond-mat.supr-con) Cite as: arXiv:1210.3172 [cond-mat.supr-con] (or arXiv:1210.3172v1 [cond-mat.supr-con] for this version) Pseudogap-related charge dynamics in layered-nickelate R2-xSrxNiO4 (x sim 1) Authors:M. Uchida, Y. Yamasaki, Y. Kaneko, K. Ishizaka, J. Okamoto, H. Nakao, Y. Murakami, Y. Tokura (Submitted on 11 Oct 2012) Abstract: Charge dynamics and its critical behavior are investigated near the metal-insulator transition of layered-nickelate R2-xSrxNiO4 (R=Nd, Eu). The polarized x-ray absorption spectroscopy experiment clearly shows the multi-orbital nature which enables the x2-y2-orbital-based checkerboard-type charge ordering or correlation to persist up to the critical doping region (x sim 1). In the barely metallic region proximate to the charge-ordered insulating phase, the nominal carrier density estimated from the Hall coefficient markedly decreases in accord with development of the pseudogap structure in the optical conductivity spectrum, while the effective mass is least enhanced. The present findings combined with the results of recent angle-resolved photoemission spectroscopy show that the pseudogap in the metalinsulator critical state evolves due to the checkerboard-type charge correlation to extinguish the coherent-motion carriers in a characteristic momentum (k)-dependent manner with lowering temperature. Comments: 7 pages, 6 figures. Accepted in Physical Review B Subjects: Strongly Correlated Electrons (cond-mat.str-el); Materials Science (cond-mat.mtrl-sci) Cite as: arXiv:1210.3093 [cond-mat.str-el] (or arXiv:1210.3093v1 [cond-mat.str-el] for this version)