DOCSLIB.ORG

Optical Properties of Tlni2se2 : Observation of Pseudogap Formation

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Optical Properties of Tlni2se2 : Observation of Pseudogap Formation Optical properties of TlNi2Se2 : Observation of pseudogap formation X. B. Wang,1 H. P. Wang,1 Hangdong Wang,2 Minghu Fang,2, 3 and N. L. Wang4,5, ∗ 1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2Department of Physics, Zhejiang University, Hangzhou 310027, China 3Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China 4International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China 5Collaborative Innovation Center of Quantum Matter, Beijing, China Quasi-two-dimensional nickel chalcogenides TlNi2Se2 is a newly discovered superconductor. We have per- formed optical spectroscopy study on TlNi2Se2 single crystals over a broad frequency range at various temper- atures. The overall optical reflectance spectra are similar to those observed in its isostructure BaNi2As2. Both the suppression in R(ω) and the peaklike feature in σ1(ω) suggest the progressive formation of a pseudogap feature in the midinfrared range with decreasing temperatures, which might be originated from the dynamic local fluctuation of charge-density-wave (CDW) instability. We propose that the CDW instability in TlNi2Se2 is driven by the saddle points mechanism, due to the existence of van Hove singularity very close to the Fermi energy. PACS numbers: 74.70.Xa,74.70.-b,74.25.Gz,74.72.Kf I. INTRODUCTION measurements14 in this weakly correlated system. More specially, the neutron pair-distribution-function The discovery of iron-based superconductors is the most (PDF) analysis in a combined high-resolution synchrotron x- significant breakthrough in the condensed matter physics in ray diffractionand neutronscattering study in KNi2Se2 reveals recent years1. The iron-pnictides/chacogenides are close to that the local charge density wave (CDW) state is present up to 300 K but disappears on cooling in the ”heavy-fermion” state magnetism and it is widely believed that the spin-fluctuation is 12,13 responsible for the pairing of the superconductingelectrons2,3. below Tcoh . Theeffect is opposite to what is typically ob- served. Moreover the ARPES did not observe any anomaly Compared with the iron-based compounds, the nickel-based 22 systems have much lower critical temperature, for example, in the spectra upon entering the fluctuating CDW state . To 4 5 understand the unique behavior, it is highly desirable to in- LaONiP (Tc = 3K) , LaONiAs (Tc = 2.7K) , BaNi2P2 6 7 vestigate the charge dynamics in the whole temperature range (Tc = 2.4K) , BaNi2As2 (Tc = 0.7K) , usually lower than 5 K even upon doping5. To date, no evidence for ordered or below 300 K. even fluctuated magnetism associated with Ni in proximity to Optical spectroscopy is a powerful bulk sensitive technique superconductivity is found. Moreover, the majority of evi- with high energy resolution, which is widely used to probe dence suggests that the Ni-based systems can be understood the carrier dynamics and possible gap formation of an elec- in context of conventional electron-phonon theory8–11. tronic system. In this work, we present a detailed optical spectroscopy study on TlNi2Se2 single crystals. Our opti- Recently, there nickel chalcogenides KNi2Se2 (Tc ≃ 12 13 cal data reveals that TlNi2Se2 is a good metal with a distinct 0.8K) , KNi2S2 (Tc ≃ 0.46K) , and TlNi2Se2 (Tc ≃ 3.7K)14 were reported, in which superconductivity ap- plasma reflectance edge, similar to its isostructure BaNi2As2. The overall frequency dependent reflectivity R(ω) is gradu- pears to involve heavy-fermion behavior below a coher- −1 15,16 ally suppressed near 2500 cm with decreasing temperature, ent temperature T ∼20 K. In contrast to K Fe − Se , coh x 2 y 2 and a pseudogapfeature appears at any temperaturebelow 300 TlNi2Se2 compound is homogeneous without Ni vacancy or phase separation12,14. Considering the monovalent Tl or K. The weak gap structure is attributed to the local CDW or- K in the stoichiometry composition, the effective valance der or fluctuations. Our measurement indicates that the lo- / of Ni in such compound is ”1.5+”. The mixed valency cal CDW order fluctuations are further enhanced at the lowest ff of Ni1.5+ was proposed to induce the heavy effective band temperature, which is di erent from the neutron PDF analy- arXiv:1507.01690v2 [cond-mat.supr-con] 28 Dec 2015 mass12,13,17. However, very recently, angle-resolved photoe- sis on KNi2Se2 in its ”heavy fermion state”. In Combination mission spectroscopy (ARPES) measurement18 reveals that with the earlier ARPES results, we suggest that the fluctuating 19 CDW instability is driven by the presence of saddle points in TlNi2Se2 shares a universal band structure with BaFe2As2 20 band structure which leads to the van Hove singularity close and BaCo2As2 , with a chemical potential shifted due to 8.5 6 to the Fermi level. more 3d electrons in TlNi2Se2 (3d ) than in BaFe2As2 (3d ) 7 and BaCo2As2 (3d ). Therefore, it can be viewed as heavily 6.5 electron doped TlFe2Se2 (3d ), with reduced electronic cor- 21 II. EXPERIMENT relations than in its cousin KxFe2−ySe2 . Furthermore, the camelback-shaped band at Z point gives rise to a pronounced van Hove singularity (VHS) near Fermi energy (EF), which Single crystals of TlNi2Se2 were grown by the self-flux provides a natural explanation to the heavy electrons behavior method14. Their structure, transport, magnetic and thermody- inferred from the electronic heat and the upper critical field namic properties were already reported14,23. The frequency- 2 dependent reflectance spectra at different temperature were 1.6 300 K ) measured by Bruker IFS 113v and 80v spectrometers in the 200 K -1 −1 100 K ∼ cm frequency range from 30 to 20 000 cm (4 meV 2.5 eV), 1 -1 − ) 1.2 1 ∼ 10 K and then the reflectance was extended to 50 000 cm ( 6.1 -1 eV) at room temperature with a grating-type spectrometer. An ( cm in situ gold and aluminum overcoating technique was used -1 0.8 to obtain the reflectivity R(ω). Considering the small size of 4 0.1 −1 our samples, the data below 100 cm are cut off for reliabil- 100 1000 10000 -1 (cm ) (10 ity. The real part of conductivity σ1(ω) is obtained by the 1 0.4 Kramers-Kronig transformation of R(ω). The Hagen-Rubens TlNi Se relation was used for low frequency extrapolation; at high fre- 2 2 quencyside, an extrapolationmethod using X-ray atomic scat- tering functions was applied to generate the high-frequency 0 3000 6000 9000 12000 24 reflectivity . -1 (cm ) FIG. 2: (Color online). Frequency dependence of the optical conduc- III. RESULTS AND DISCUSSION tivity below 12 000 cm−1 at different temperatures. The inset shows −1 σ1(ω) over broad frequencies up to 50 000 cm on a logarithm scale. Figure 1 shows the reflectance spectra of TlNi2Se2 single crystals over a broad energy scale at various temperatures. The value of R(ω) approaches unity towards zero energy and eral temperature-independent interband transitions could be shows an increase with decreasing temperature, indicating a also well resolved, as shown in the inset of Figure 2. The op- −1 good metallic behavior. By lowering the temperature, we do tical conductivity between 500 and 10 000 cm is gradually not see any sharp changes in the optical spectra but rather suppressed and a broad peak-like feature becomes more and −1 weak suppression of R(ω) near 2500 cm−1 , signaling the more obvious at 2800 cm as the temperature decreases. The 26 opening of a partial gap (pseudogap). With increasing ω, spectral line shape is similar to that of BaFe2As2 across the R(ω) drops quickly near 7000 cm−1 , known as the screened SDW transition though the feature is much weaker. It seems plasma edge. The relativity high edge position reveals a high to suggest that there should also be a density-wave gap open- carrier density, which is similar to isostructural compound, ing in TlNi2Se2 . Furthermore, this pseudogap feature is most 25 BaNi2As2 . There is another edge structure at about 15 000 prominent at low temperature and can be resolved even in the cm−1 which is caused by an interband transition. The reflec- 300 K data. tivity becomes roughly temperature independent at higher fre- To quantify the temperature evolution of optical conductiv- quencies. The inset of Fig. 1 shows R(ω) data up to 50 000 ity, especially the low frequency components, we use a sim- cm−1 in a logarithmic scale at 300 K. ple Drude-Lorentz model to decompose optical conductivity 27 Figure 2 shows the real part of conductivity spectra below spectra : 12 000 cm−1 at different temperatures. The Drude-type con- 2 2 2 ωpi Γ S j Γ jω ductivity is observed for all spectra at low frequency and sev- σ (ω) = Di + (1) 1 X 4π 2 + Γ2 X 4π 2 − 2 2 + 2Γ2 i ω Di j (ω j ω ) ω j 1.0 where ωpi and ΓDi are the plasma frequency and the relax- 0.8 ation rate of each conduction band, while ω j, Γ j and S j are 0.6 the resonance frequency, the damping and the mode strength R 0.8 300 K of each Lorentz oscillator, respectively. This model includes 0.4 Drude and Lorentz terms, which approximately capture the 100 1000 10000 contribution by free carriers and interband transitions. Both TlNi Se -1 2 2 (cm ) 14,23 18 transport and ARPES results suggest the multiband 0.6 R character of TlNi2Se2 , therefore we applied two Drude com- 300 K ponents analysis here, similar to the other members of ”122” 200 K 25–27 100 K system . Even though the Drude-Lorentz fit is somewhat 0.4 10 K arbitrary and the accuracy of the derived fit parameters is un- certain, it will not modify the key outcomes of the analysis.
Load more

Recommended publications
  • Vortex-Matter in Multi-Component Superconductors
    Vortex-matter in Multi-component Superconductors JOHAN CARLSTRÖM Licentiate thesis Stockholm, Sweden 2012 TRITA-FYS 2012:90 ISSN 0280-316X KTH Teoretisk fysik ISRN KTH/FYS/--12:90--SE AlbaNova universitetscentrum ISBN 978-91-7501-611-5 SE-106 91 Stockholm Sweden Akademisk avhandling som med tillstånd av Kungl Tekniska högskolan framlägges till offentlig granskning för avläggande av teknologie licentiatexamen i teoretisk fysik den 14 Januari 2013 kl 10:00 i sal FA32, AlbaNova Universitetscentrum. c Johan Carlström, December 2012 Tryck: Universitetsservice US AB 3 Abstract The topic of this thesis is vortex-physics in multi component Ginzburg- Landau models. These models describe a newly discovered class of supercon- ductors with multiple superconducting gaps, and posses many properties that set them apart from single component models. The work presented here relies on large scale computer simulations using various numerical techniques, but also some analytical methods. In Paper I, Type-1.5 Superconducting State from an Intrinsic Proximity Effect in Two-Band Superconductors, we show that in multiband supercon- ductors, even an extremely small interband proximity effect can lead to a qualitative change in the interaction potential between superconducting vor- tices by producing long-range intervortex attraction. This type of vortex interaction results in an unusual response to low magnetic fields, leading to phase separation into domains of two-component Meissner states and vortex droplets. In paper II, Type-1.5 superconductivity in multiband systems: Effects of interband couplings, we investigate the appearance of Type-1.5 superconduc- tivity in the case with two active bands and substantial inter-band couplings.
    [Show full text]
  • Theory of Nematic Fractional Quantum Hall State
    Theory of Nematic Fractional Quantum Hall State Yizhi You,1 Gil Young Cho,1 and Eduardo Fradkin1, 2 1Department of Physics and Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080, USA 2Kavli Institute for Theoretical Physics, University of California Santa Barbara, CA 93106-4030, USA (Dated: July 9, 2018) We derive an effective field theory for the isotropic-nematic quantum phase transition of fractional quantum Hall (FQH) states. We demonstrate that for a system with an isotropic background the low-energy effective theory of the nematic order parameter has z = 2 dynamical scaling exponent, due to a Berry phase term of the order parameter, which is related to the non-dissipative Hall viscosity. Employing the composite fermion theory with a quadrupolar interaction between electrons, we show that a sufficiently attractive quadrupolar interaction triggers a phase transition from the isotropic FQH fluid into a nematic fractional quantum Hall phase. By investigating the spectrum of collective excitations, we demonstrate that the mass gap of Girvin-MacDonald-Platzman (GMP) mode collapses at the isotropic-nematic quantum phase transition. On the other hand, Laughlin quasiparticles and the Kohn collective mode remain gapped at this quantum phase transition, and Kohn’s theorem is satisfied. The leading couplings between the nematic order parameter and the gauge fields include a term of the same form as the Wen-Zee term. A disclination of the nematic order parameter carries an unquantized electric charge. We also discuss the relation between nematic degrees of freedom and the geometrical response of the fractional quantum Hall fluid.
    [Show full text]
  • Media Highlights
    2008 Applied Superconductivity Conference and Exhibition August 17 – 22. 2008 Hyatt Regency Chicago – Chicago, IL USA MEDIA HIGHLIGHTS Conference Website: http://www.ascinc.org PRESS REGISTRATION Members of the media may register by faxing a registration form (found at www.ascinc.org) to ASC 2008 Press at (303) 499- 2599, or register on-site at the Registration desk, located in the North Grand Ballroom Foyer of the Hyatt Regency Chicago. Journalists will be asked to show press credentials/ID to receive complimentary admission to technical sessions, welcome reception and exhibitor’s reception, and Exhibition Hall. Conference program, badges and other conference materials will be available at the registration desk. Tickets for the Thursday conference luncheon may also be purchased at the desk. On-site Press Registration: North Grand Ballroom Foyer – Hyatt Regency Chicago Hours of Operation: Sunday, August 17: 2:00 p.m. – 8:00 p.m. Monday, August 18: 7:00 a.m. – 7:00 p.m. Tuesday, August 19: 7:00 a.m. – 6:00 p.m. Wednesday, August 20: 7:00 a.m. – 6:00 p.m. Thursday, August 21: 7:00 a.m. – 6:00 p.m. Friday, August 22: 7:00 a.m. – 12:00 Noon (For media assistance and additional information, please ask for Dr. Balu Balachandran, Mr. Jim Kerby, Dr. Lance Cooley, Ms. Sue Butler, or Mrs. Paula Pair. Individual interview rooms may also be scheduled.) PLENARY AND OTHER SPECIAL SESSIONS Monday, August 18, 8:00 a.m. - 9:00 a.m. Welcome – Dr. Balu Balachandran, Argonne National Laboratory (Conference Chair); Opening Remarks – Dr.
    [Show full text]
  • Zlatko Tesanovic
    Zlatko Tesanovic Zlatko was born in Sarajevo (former Yugoslavia) on August 1, 1956 and passed away on July 26, 2012. InsItute for Quantum Maer, Johns Hopkins-Princeton Posions 1994-2012: Professor, Johns Hopkins University 1990-1994: Associate Professor, Johns Hopkins University 1987-1990: Assistant Professor, Johns Hopkins University 1987-1988: Director's Postdoctoral Fellow (on leave from JHU), Los Alamos Naonal Laboratory 1985-1987: Postdoctoral Fellow, Harvard University Educaon 1980-1985: Ph.D. in Physics, University of Minnesota 1975-1979: B.Sc. in Physics (Summa cum Laude), University of Sarajevo, former Yugoslavia Fellowships, Awards, Honors Foreign Member, The Royal Norwegian Society of Sciences and LeLers Fellow, The American Physical Society, Division of Condensed Maer Physics Inaugural Speaker, J. R. Schrieffer Lecture Series, Naonal High MagneIc Field Laboratory, 1997 David and Lucille Packard Foundaon Fellowship, 1988-1994 J. R. Oppenheimer Fellowship, Los Alamos Naonal Laboratory, 1985 (declined) Stanwood Johnston Memorial Fellowship, University of Minnesota, 1984 Shevlin Fellowship, University of Minnesota, 1983 Fulbright Fellowship, US InsItute of Internaonal Educaon, 1980 Zlatko Tesanovic Graduate Students (10) L. Xing (Jacob Haimson Professor, Stanford), I. F. Herbut (Professor, Simon Fraser University, Canada), A. Andreev (Associate Professor, University of Washington), S. Dukan (Professor and Chair of Physics, Goucher College), O. Vafek (Associate Professor, Florida State University and NHMFL), A. Melikyan (Editor, Physical Review B), Andres Concha (Postdoctoral Fellow, Harvard), ValenIn Stanev (Postdoctoral Fellow, Argonne NL), Jian Kang (current), James Murray (current) Postdoctoral Advisees (9) A. Singh (Professor, IIT Kanpur, India), S. Theodorakis (Professor, University of Cyprus, Cyprus), J. H. Kim (Professor and Chair of Physics, University of North Dakota), Z.
    [Show full text]
  • Quantum Critical Behavior in the Superfluid Density of High-Temperature Superconducting Thin Films
    QUANTUM CRITICAL BEHAVIOR IN THE SUPERFLUID DENSITY OF HIGH-TEMPERATURE SUPERCONDUCTING THIN FILMS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Iulian N. Hetel, Maitrise de Physique et Applications, M.S. Physics ***** The Ohio State University 2008 Dissertation Committee: Approved by Professor Thomas R. Lemberger, Adviser Professor Klaus Honscheid Adviser Professor R. Sooryakumar Physics Graduate Program Professor Nandini Trivedi ABSTRACT A central question in the physics of high-temperature superconductors is how su- perconductivity is lost at the extreme ends of the superconducting phase diagram, underdoping and overdoping. When mobile holes are removed from optimally doped cuprates, the transition temperature TC and superfluid density nS(0) decrease in a surprisingly correlated fashion. I succeeded in producing and measuring homoge- neous underdoped high-temperature superconducting films by partially substituting +2 +3 Ca for Y in Y Ba2Cu3O7−δ films with reduced oxygen concentrations in the CuO chains. I test the idea that the physics of underdoped cuprates is dominated by phase fluc- tuations by measuring the temperature dependence of superfluid density nS(T ) and by changing the dimensionality of the system from 3D thick samples to 2D ultrathin films. Thick Y1−xCaxBa2Cu3O7−δ films are in agreement with previous measure- ments of pure Y Ba2Cu3O7−δ samples and do not show any 2D or 3D-XY critical regimes in the temperature dependence of superfluid density. Moreover, the tran- sition temperature has a square-root dependence on absolute superfluid density at zero temperature, rather than showing the predicted linear dependence in the case of strong thermal phase fluctuations.
    [Show full text]
  • Curriculum Vitae
    Curriculum Vitae Predrag Nikolić George Mason University, School of Physics, Astronomy and Computational Sciences Planetary Hall #209, MSN 3F3, Fairfax, VA 22030 USA Phone: 509-460-9066; E-Mail: [email protected]; www: http://physics.gmu.edu/~pnikolic/ Academic Positions George Mason University, Assistant Professor 08/25/2009 ± present Johns Hopkins University, Adjunct Assistant Professor 09/01/2009 ± present National Institute for Standards and Technology, Guest Researcher 09/01/2009 ± 07/01/2011 Rice University, Keck Postdoctoral Fellow 08/01/2007 ± 07/31/2009 Harvard University, Postdoctoral Fellow 09/01/2005 ± 07/31/2007 Yale University, Postdoctoral Associate 09/01/2004 ± 08/31/2005 Columbia University, Visiting Scientist 09/01/2004 ± 08/31/2005 Education Massachusetts Institute of Technology, Ph.D. in Theoretical Physics 2004 thesis: Geometrically Frustrated Quantum Magnets (advisor: T. Senthil) 09/01/2001 ± 09/15/2004 experimental physics research assistantship (advisor: R. Ashoori) 07/15/1998 ± 08/31/2001 University of Belgrade, Serbia, B.S. in Applied Physics 1998 thesis: Quantum Interference Transistors (advisor: K.Nikolić) 09/01/1993 ± 07/01/1998 Research Grants and Awards NSF Award #1205571 (PI): ªCollaborative Research: 2012 ± 2015 Correlated Superfluids and Insulators of Ultracold Fermionic Atomic Gasesº GMU part: $150,000 for 3 years Publication Award, George Mason University, College of Science November 2011 Johns Hopkins University, IQM summer researcher 2010 ± 2014 Rice University, Keck Fellowship 2007 ± 2009 Madlena
    [Show full text]
  • OSKAR VAFEK Curriculum Vitae Department of Physics and National
    OSKAR VAFEK curriculum vitae Department of Physics and National High Magnetic Field Laboratory tel.(NHMFL A319) : (850) 644-0848 Florida State University tel.(KEEN 309) : (850) 508-7377 Tallahassee, Florida 32306 fax. : (850) 644-5038 USA e-mail: [email protected] Education and Degrees Sep 2003 - Sep 2006 Stanford University, Stanford, CA Postdoctoral Scholar Stanford Institute for Theoretical Physics June 1998 - Aug 2003 Ph.D. Johns Hopkins University (physics) Thesis advisor: Prof. Zlatko Tesanovic Aug 1994 -May 1998 B.A. Goucher College (major: chemistry, minors: physics, mathematics) Positions held: 2012 - present Associate Professor (with tenure) National High Magnetic Field Laboratory Department of Physics, Florida State University 2006 - 2012 Assistant Professor National High Magnetic Field Laboratory Department of Physics, Florida State University 2003 - 2006 Postdoctoral Scholar Stanford University Institute for Theoretical Physics 1998 - 2003 Research Assistant Department of Physics and Astronomy, Johns Hopkins University Research interests Theoretical condensed matter physics and statistical field theory, with an emphasis on the problems in superconductivity and strongly correlated systems Awards and honors 2012 Florida State University PAI Award for excellence in teaching and research 2010 NSF Career Award 2003 Stanford ITP Fellowship (Stanford University) 1998 Ellen E. Swomley Fellowship (Johns Hopkins University) 1998 Stimson-Duvall Scholarship (Goucher College) Luise Kelly Prize in Chemistry (Goucher College) Phi Beta Kappa Membership 1997 NSF Research Opportunity Award for summer research at Johns Hopkins U. 1997 Presidential Scholarship for the senior project (Goucher College) 1994 Merit Foreign Student Scholarship full 4-year scholarship to attend Goucher College Journal publications and preprints: 1. R.M. Fernandes and O.
    [Show full text]
  • 1 Program and Abstract Booklet Workshop On
    1 PROGRAM AND ABSTRACT BOOKLET WORKSHOP ON CORRELATIONS AND COHERENCE IN QUANTUM SYSTEMS University of Evora,´ Portugal, 8-12 October 2012 2 This workshop is dedicated to the memory of Adilet Imambekov and Zlatko Tesanovic, speakers of previous workshops held in Evora.´ In Memoriam - Adilet Imambekov (Speaker in the Workshop on Correlations and Coherence in Quantum Matter Evora,´ Portugal, 10-14 November 2008) An outstanding young physicist, Adilet Imambekov, passed away on July 18, 2012 on Khan Tengri mountain in Kyrgyzstan. Adilet was only 30. Despite his short career, Adilet’s presence in quantum condensed matter and cold atoms communities was prominent. His work had a strong impact on non-equilibrium physics of low- dimensional systems, and was widely recognized by colleagues. One of his recent remarkable contribution is the universal theory of nonlinear Luttinger liquids. Adilet received his B.Sc. degree summa cum laude from Moscow Institute of Physics and Technology in 2002. He did his PhD at Harvard University with Prof. Demler, working on cold atoms and exactly solvable models. Following a two-year postdoc at Yale, Adilet took a position of assistant professor at Rice University in 2009. Adilet was a highly interactive, warm, and genuinely kind person. He was among the key participants of many conferences and workshops, and had many close friends both in physics and in climbing communities. In Memoriam - Zlatko Tesanovic (Invited speaker in the Work- shop on Quantum coherence and correlations in condensed-matter and cold-atom systems, Evora,´ Portugal, 11-15 October 2010) Zlatko Tesanovic passed away on July 26, 2012 of an apparent heart attack.
    [Show full text]
  • Spin-Orbit Physics in the Mott Regime Leon Balents, KITP “Exotic Insulating State of Matter”, JHU, January 2010 Collaborator
    Spin-orbit physics in the Mott regime Leon Balents, KITP “Exotic Insulating State of Matter”, JHU, January 2010 Collaborator Dymtro Pesin UT Austin Topological Insulators Exotic Insulating States of Matter » Scientific Program http://icamconferences.org/jhu2010/scientific-program/ Exotic Insulating States of Matter » Scientific Program http://icamconferences.org/jhu2010/scientific-program/ Exotic Insulating States of Matter » Scientific Program http://icamconferences.org/jhu2010/scientific-program/ 7:30 PM Dinner on own 8:00 AM Breakfast Exotic Insulating States of Matter » Scientific Friday, January 15th Novel States: Program 8:00 AM Breakfast 9:00 AM Moses Chan: Is supersolid a superfluid? 9:30 AM Matthew Fisher: Spin Bose-Metals in Weak Mott Insulators Higher-T superconductors: Thursday, January 14th c 10:00 AM Leon Balents: Spin-orbit physics in the Mott regime 9:00 AM Zlatko Tesanovic: Correlated superconductivity in cuprates and pnictides 8:00 AM Breakfast and Registration 9:30 AM Andrei Bernevig: Nodal and nodeless superconductivity in the iron based 10:30 AM Break 8:55 AM Greeting – Welcome superconductors Transport in Topological Insulators: 10:00 AM John Tranquada: Striped Superconductivity in La2-xBaxCuO4 Topological Insulators: 11:00 AM Ashvin Vishwanath: Topological Defects and Entanglement in Topological Insulators 9:00 AM S.-C. Zhang: Topological insulators and topological superconductors 10:30 AM Break 11:30 AM Phuan Ong: Transport Experiments on topological insulators Bi Se and Bi Te 9:30 AM Charles Kane: Topological Insulators
    [Show full text]
  • The Rise of Topological Quantum Entanglement (7.0Mb Pdf)
    TheThe riserise ofof topologicaltopological quantumquantum entanglemententanglement PredragPredrag NikoliNikolićć GeorgeGeorge MasonMason UniversityUniversity InstituteInstitute forfor QuantumQuantum MatterMatter @@ JohnsJohns HopkinsHopkins UniversityUniversity The College of William & Mary September 5, 2014 Acknowledgments Collin Broholm Wesley T. Fuhrman US Department National Science IQM @ Johns Hopkins Johns Hopkins of Energy Foundation Michael Levin Zlatko Tešanović University of Maryland IQM @ Johns Hopkins The rise of topological quantum entanglement 2/30 Overview • Introduction to strongly correlated TIs – What we already (hopefuly) know – Kondo TIs • Correlations on Kondo TI boundaries – Predictions of new physics – Hybridized regime: SDW, SC, spin liquids... – Local moment regime: AF metal, QED3... • Exotic quantum states in TI quantum wells – Novel vortex states Color codes: Relax – Fractional incompressible quantum liquids Cool Really? Watch out! The rise of topological quantum entanglement 3/30 Fundamental Questions How to understand nature? What is it made of? How is it organized? (particle physics) (condensed matter physics) Collective behavior of many particles Emergent phenomena Critical phenomena (phases of matter) (lose the sight of microscopics) The rise of topological quantum entanglement 4/30 Correlations By interactions between particles Long-range order (spontaneous symmetry breaking) By quantum entanglement ∣Schrödinger©s cat〉=∣alive〉+∣dead〉 The rise of topological quantum entanglement 5/30 Topological vs. Conventional
    [Show full text]
  • Quantum Hall Ferromagnets
    QUANTUM HALL FERROMAGNETS AKSHAY KUMAR ADISSERTATION PRESENTED TO THE FACULTY OF PRINCETON UNIVERSITY IN CANDIDACY FOR THE DEGREE OF DOCTOR OF PHILOSOPHY RECOMMENDED FOR ACCEPTANCE BY THE DEPARTMENT OF PHYSICS ADVISER:SHIVAJI L. SONDHI APRIL 2016 c Copyright by Akshay Kumar, 2016. All rights reserved. Abstract We study several quantum phases that are related to the quantum Hall effect. Our initial focus is on a pair of quantum Hall ferromagnets where the quantum Hall ordering oc- curs simultaneously with a spontaneous breaking of an internal symmetry associated with a semiconductor valley index. In our first example – AlAs heterostructures – we study domain wall structure, role of random-field disorder and dipole moment physics. Then in the second example – Si(111) – we show that symmetry breaking near several integer filling fractions involves a combination of selection by thermal fluctuations known as “order by disorder” and a selection by the energetics of Skyrme lattices induced by moving away from the commensurate fillings, a mechanism we term “order by doping”. We also study ground state of such systems near filling factor one in the absence of valley Zeeman energy. We show that even though the lowest energy charged excitations are charge one skyrmions, the lowest energy skyrmion lattice has charge >1 per unit cell. We then broaden our discussion to include lattice systems having multiple Chern num- ber bands. We find analogs of quantum Hall ferromagnets in the menagerie of fractional Chern insulator phases. Unlike in the AlAs system, here the domain walls come naturally with gapped electronic excitations. We close with a result involving only topology: we show that ABC stacked multilayer graphene placed on boron nitride substrate has flat bands with non-zero local Berry curva- ture but zero Chern number.
    [Show full text]
  • Education Reseach Teaching References Interests
    Curriculum Vitae Qijin Chen Page 1 of 4 Qijin Chen Shanghai Branch, Hefei National Laboratory for Physical Sciences at Microscale, the University of Science and Technology of China, 99 Xiupu Rd, Pudong, Shanghai #$%&%', CHIN); Email: [email protected] EDUCATION Ph.D., University of Chicago Chicago, (L #$$$ Theoretical Condensed Matter Physics M.S., Instit te of Physics, Chinese Aca!emy of Sciences #CAS$ Bei0ing, China %99' +3!eri,ental Condensed Matter Physics %.S. #with honor$, Univ. of Science an! Techno&ogy of China #USTC$ Hefei, China %99# N clear and Particle Physics/Theoretical Physics PRO(ESSIONA) EMPLOYMENTS University of Science an! Techno&ogy of China Hefei 5 Shanghai, China #$%9-!resent 6isting ished Professor, Hefei National Laboratory for Physical Sciences at Microscale +hejiang University Hang7ho , China #$$8-#$%9 6isting ished Professor, 9he0iang (nstit te of Modern Physics and 6e!art,ent of Physics University of Chicago Chicago, (L #$$:-#$$8 "esearch associate and "esearch Scientist, Ja,es <ranck (nstit te Argonne Nationa& )a, - University of Notre Da"e )rgonne, (L S ,,er, #$$: >isiting <ello?, (nstit te for Theoretical Sciences .ohns /o01ins University Balti,ore, M6 #$$# @#$$: Postdoctoral <ello?, 6e!art,ent of Physics and )strono,y2 )dvisor- 9lat=o Tesanovic Nationa& /igh Magnetic (ie&! )a,oratory Tallahassee, <L #$$$@#$$# Postdoctoral "esearch )ssociate, Condensed Matter Theory Aro ! )dvisor- ;2 "obert SchrieBer University of Chicago Chicago, (L %99C@#$$$ "esearch )ssistant, Ja,es <ranck (nstit te )dvisor- Dathryn Levin Instit te of Physics, Chinese Aca!emy of Sciences Bei0ing, China %99&@%99' "esearch )ssistant, State Dey Laboratory of S rface Physics )dvisor- 9hangda Lin /ONO'S AND A2A'DS • #$$9, EChang0iang ScholarF Professorshi!, Ministry of +d cation, China • %99C, First Prize in Natural Sciences, Chinese )cade,y of Sciences GJointly ?ith 9262 Lin, D2)2 <eng, ;2 Hang and B2I2 S nJ, the most prestigious award of CAS2 • #$$:, >isiting <ello?, (nstit te for Theoretical Sciences, )rgonne NatKl Lab 5 Univ.
    [Show full text]