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X-WR-CALNAME:Dirac Materials
X-ORIGINAL-URL:http://diracmaterials.org
X-WR-CALDESC:Events for Dirac Materials
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TZID:"Europe/Stockholm"
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DTSTART:20190331T010000
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DTSTART:20191027T010000
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DTSTART;TZID="Europe/Stockholm":20190903T100000
DTEND;TZID="Europe/Stockholm":20190903T110000
DTSTAMP:20260504T225150
CREATED:20190830T142740Z
LAST-MODIFIED:20190830T142740Z
UID:1233-1567504800-1567508400@diracmaterials.org
SUMMARY:[Talk] Shota Kanasugi - Spin-orbit-coupled ferroelectric superconductivityand multiorbital effects in SrTiO3
DESCRIPTION:Speaker: Shota Kanasugi\nAffiliation: Kyoto University \nTitle: Spin-orbit-coupled ferroelectric superconductivityand multiorbital effects in SrTiO3 \nAbstract: A lot of exotic superconducting statesemerge close to other ordered phases\, such as anisotropic superconductivity in cuprates. Although previous studies have mainly focused on the superconductivityclose to magnetic instability\, the ferroelectric (FE) counterpart is recently receiving increased attention since such superconductivity was reported in doped SrTiO3(STO). STO is a unique compound which exhibits both quantum paraelectricity and superconductivity. The superconducting transition temperature is enhanced in the vicinity of the FE quantum critical point [1-4]. Moreover\, recent experiments suggest the coexistence ofsuperconductivity and ferroelectricity in doped STO [2]. These results imply a cooperative correlation between superconductivity and ferroelectricity against a long-held belief that they should be incompatible.In this talk\, we present that aFE-like polar inversion symmetry breaking order can be controlled by the superconductivityin spin-orbit coupled systems. We introduce a model of electron-lattice coupled two-dimensional superconductor\,in which the ferroelectricity-induced Rashba spin-orbit coupling [5]is included. It is shown that the FE superconductivity\,which is characterized by a FE structural transition in the superconducting state\,is realized through two different mechanisms [6]. First\, the FE superconducting state is stabilized by the Lifshitz transition of the Rashba split bandsin lowcarrier density regimes.Second\, the FE superconductingstate is stabilized under a Zeeman magnetic field\, thanksto the suppressionof the Pauli depairingeffect in the FE phase. Furthermore\, we show that the FE superconductivity in bulk STO is strongly affected by the multiorbital effectoft2gelectrons[7]. Then\, we predict a topologicalWeyl superconducting state in the FE superconducting phase of bulk STO. \nReferences\n[1] A. Stucky et al.\, Sci. Rep. 6\,37582 (2016).\n[2] C. W. Rischau et al.\, Nat. Phys. 13\, 643 (2017).\n[3] Y. Tomioka et al.\, Nat. Commun. 10\, 738 (2019).\n[4] K. Ahadi et al.\, Sci. Adv. 5\, eaaw0120 (2019).\n[5] G. Khalsa\, B. Lee\, and A. H. MacDonald\, Phys. Rev. B 88\, 041302 (2013).\n[6] S. Kanasugi and Y. Yanase\, Phys. Rev. B 98\, 024521 (2018).\n[7] S. Kanasugi and Y. Yanase\, arXiv: 1904.11113 (2019) \n
URL:http://diracmaterials.org/calendar2/talk-shota-kanasugi-spin-orbit-coupled-ferroelectric-superconductivityand-multiorbital-effects-in-srtio3/
LOCATION:NORDITA // South  (Meeting Room 112.006B)\, Roslagstullsbacken 23\, Stockholm\, 106 91\, Sweden
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DTSTART;TZID="Europe/Stockholm":20190903T110000
DTEND;TZID="Europe/Stockholm":20190903T120000
DTSTAMP:20260504T225150
CREATED:20190903T081516Z
LAST-MODIFIED:20190903T081621Z
UID:1240-1567508400-1567512000@diracmaterials.org
SUMMARY:[CMT SEMINAR] Ipsita Mandal - Some aspects of correlated electrons
DESCRIPTION:Speaker: Ipsita Mandal \n\nAffiliation: University of Stavanger\,\n\n\nTitle: Some aspects of correlated electrons\,\n \nTime:  Fika 10:30-11:00 \, Seminar 11:00-12:00\,\nPlace: Nordita South\, room 112:028 .\n\nAbstract:\nIn this talk\, I am going to present exciting results from two of my ongoing/recent projects.\nFirst part:\nSpin-orbit coupling (SOC) assisted (spin j = 1/2) Mott insulators exhibiting bond-directional exchange interactions are expected to exhibit unconventional quantum magnetic phases like spin liquids [1\, 2] predicted by the Kitaev model\, dubbed as Kitaev spin liquid (KSL). The feature of a Kitaev material is that the Kitaev coupling is the dominant exchange coupling. Compounds like honeycomb iridates and α-RuCl_3 have been identified as candidate Kitaev materials. In the first part of my talk\, I will address the unresolved question whether α-RuCl_3 is actually a Kitaev material. If yes\, what is the value of the Kitaev coupling strength? If not\, what are the dominant terms in the effective spin Hamiltonian that can describe the system? We focus on the results from resonant torsion magnetometry experiments by Modic et al\, which they can measured the magnetotropic coefficient k\, when a magnetic field B is applied making angle θ with the c-axis of the crystal. Using a simple Hamiltonian with a dominant paramagnetic term\, we will show that we can fit the data obtained in the experiments.\n \nSecond part:\nIn sufficiently clean metals\, it is possible for electrons to collectively flow as a viscous fluid at finite temperature. These viscous effects have been predicted to give a notable magneto resistance\, but whether the magnetoresistance is positive or negative has been debated. We argue that regardless of the strength of inhomogeneity\, bulk magnetoresistance is always positive in the hydrodynamic regime.\n  \n
URL:http://diracmaterials.org/calendar2/cmt-seminar/
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BEGIN:VEVENT
DTSTART;TZID="Europe/Stockholm":20190903T120000
DTEND;TZID="Europe/Stockholm":20190903T130000
DTSTAMP:20260504T225150
CREATED:20190830T143303Z
LAST-MODIFIED:20190903T081156Z
UID:1235-1567512000-1567515600@diracmaterials.org
SUMMARY:[Talk] Manuel Simonato - On the Spectral Properties of Inhomogeneous Luttinger Liquids
DESCRIPTION:Speaker: Manuel Simonato \nTitle: On the spectral properties of inhomogeneous Luttinger liquids \nAbstract: The physics of one-dimensional systems of interacting fermions strongly differs from the picture offeredby Fermi liquid theory. The low-energy properties of metallic\, paramagnetic 1D Fermi systems arewell described by the Luttinger liquid (LL) theory. Among other properties\, the homogeneous LL isknown to exhibit power-law behaviour for various correlation functions. For spin rotational invariantmodels\, the exponents can be expressed in terms of a single parameterKρ\, which is known to benon-universal.The LL concept emerged in the study of homogeneous systems with periodic boundary condition(PBC). In these models thelocal spectral functionshows a power-law suppression at energies asymp-totically close to the chemical potentialμ. Theoretically\, this is very well understood and the exactLL parameterKρis known for a set of integrable models. In the last decades however\, the interestshifted towards the investigation of LLs with PBC including impurities. The fact that these systemshave been shown to scale to chains with open ends led to the study of several models where openboundary condition (OBC) are introduced. As the translational invariance is broken\, the exponent ofthe power-law suppression close to the boundary differs from the one in the bulk.The present work is devoted to the study of the local spectral function of two lattice models of LLswith open boundaries\, namely the spinless fermions model with nearest neighbour interaction and the1D Hubbard model\, with the methods of perturbation theory. It is demonstrated that many aspectsof the spectral properties can be understood within the HF theory. Despite what one usually readsabout one-dimensional interacting Fermi systems\,in the presence of the boundaryperturbation theoryis already capable of providing meaningful results. Concurrently\, this method also allows us to developan understanding of the dip appearing in the local spectral function at an energy different from thechemical potential. \n
URL:http://diracmaterials.org/calendar2/1235/
LOCATION:NORDITA // South  (Meeting Room 112.006B)\, Roslagstullsbacken 23\, Stockholm\, 106 91\, Sweden
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