Bulletin of the American Physical Society
2017 Annual Meeting of the APS Mid-Atlantic Section
Volume 62, Number 19
Friday–Sunday, November 3–5, 2017; Newark, New Jersey
Session M2: CMP-QM: Superconductivity and Strongly Correlated Systems - II |
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Chair: Girsh Blumberg, Rutgers University Room: 240, Campus Center, NJIT |
Sunday, November 5, 2017 10:00AM - 10:36AM |
M2.00001: Collective phenomena in correlated electron systems: superconductivity and density waves Invited Speaker: Girsh Blumberg Interaction between electrons in “strongly correlated materials” is associated with many scientifically important and technologically useful phenomena, including superconductivity and exotically ordered charge and spin phases. I will review the recent advances of Raman spectroscopy aimed to characterize these extraordinary self-organized electronic phases, determine the condition under which they are formed, identify the underlying microscopic mechanisms, and test the relevant theories.\\[2mm] Research at Rutgers was done in collaboration with H.-H. Kung, S.-F. Wu, M. Ye, Weilu Zhang. [Preview Abstract] |
Sunday, November 5, 2017 10:36AM - 10:48AM |
M2.00002: Photoinduced Nonequilibrium Dynamics in Charge Density Wave Materials Linghua Zhu, Keun Hyuk Ahn, Tsezar F. Seman, Michel van Veenendaal We study the dynamics of photoinduced phase transitions in charge density wave (CDW) systems of the Peierls instability and analyze the interplay among electrons, periodic lattice distortions, and a phonon thermal reservoir in nonequilibrium states. Simulations based on a tight-binding Hamiltonian and Boltzmann equations reveal partially decoupled oscillations of the CDW order parameter and the periodic lattice distortion during CDW melting, and nonthermal electron distribution during CDW refreezing. The cooling rate of the electron system is found to be sensitively dependent on the CDW gap dynamics. The CDW melting becomes more energy efficient with lower photon energy and the coherent oscillation becomes slower with the lower pump fluence, consistent with the Kohn anomaly. Qualitative agreement is found between key features of the simulations and experiments, which demonstrates the intricate nonequilibrium dynamics in CDW materials. [Preview Abstract] |
Sunday, November 5, 2017 10:48AM - 11:00AM |
M2.00003: Non-equilibrium electron and lattice dynamics in Bi-2212 Tatiana Konstantinova, Jonathan Rameau, Alexander Reid, Lijun Wu, Genda Gu, Alexander Kemper, Hermann Durr, Uwe Bovensiepen, Peter Johnson, Xijie Wang, Yimei Zhu Here I present a study of the non-equilibrium lattice dynamics in a cuprate system, Bi-2212, performed by combining time- and angle-resolved photoelectron spectroscopy and MeV ultrafast electron diffraction. We have conducted the one-to-one comparison between electron and lattice dynamics in this material with 100 fs temporal resolution and established a picture of the energy flow within these two subsystems from the 1.55 eV photon absorption till formation of the acoustic waves. At the sub-picosecond time scale the dynamics is dominated by the electron coupling to the hot phonon, which we have identified through the quantitative analysis of the diffraction pattern changes as the in-plane Cu-O bond-stretching mode. Later dynamics is dominated by the anharmonic decay of the hot phonon to the lower energy modes, while the coupling strength of the electrons to these modes is low. The analysis of the thermal diffuse scattering in the electron diffraction demonstrates that the higher energy optical branches populate faster than the lower energy optical and acoustic branches, leading to a non-thermal phonon distribution, that, along with other observations, questions the validity of the N-temperature model for the cuprates. [Preview Abstract] |
Sunday, November 5, 2017 11:00AM - 11:36AM |
M2.00004: What Stripes Tell Us about Superconductivity in Cuprates Invited Speaker: John Tranquada Doping holes into the correlated-insulator state of CuO$_{\mathrm{2}}$ planes frustrates the antiferromagnetic order and leads to an inhomogeneous state that can take the form of charge and spin stripes. The reduced dimensions of the spin stripes lead to the development of a singlet-triplet gap, while the interaction of the charge carriers with this environment can yield electron pairing. Rather than acting as a competing order, this intertwining of spin and charge correlations can result in superconductivity [1]. In particular, two-dimensional superconductivity has been observed to coexist with stripe order [2], and features of the resulting state have been explained by invoking the concept of a pair-density-wave superconductor [3]. The presence of real-space modulations presents a challenge for the conventional foundation of superconductivity theory, which is a gas of quasiparticles described only in terms of their momenta. Moreover, various spectroscopic measurements of striped and uniform cuprate superconductors look quite similar; hence, it seems likely that the pairing mechanism is common to cuprates spanning the range of hole doping. I will discuss the experimental picture, including recent evidence for the coexistence of truly static charge order [4] and gapless spin fluctuations [5,6] with superconductivity, and the implications for our understanding of these materials. [1] E. Fradkin, S. A. Kivelson, and J. M. Tranquada, Rev. Mod. Phys. \textbf{87}, 457 (2015). [2] Q. Li \textit{et al.}, Phys. Rev. Lett. \textbf{99}, 067001 (2007). \textunderscore [3] E. Berg, E. Fradkin, S. A. Kivelson, and J. M. Tranquada, New J. Phys. \textbf{11}, 115004 (2009). \textunderscore [4] X. M. Chen \textit{et al.}, Phys. Rev. Lett. \textbf{117}, 167001 (2016). [5] Z. J. Xu \textit{et al}., Phys. Rev. Lett. \textbf{113}, 177002 (2014). [6] H. Jacobsen \textit{et al}., Phys. Rev. B \textbf{92}, 174525 (2015). [Preview Abstract] |
Sunday, November 5, 2017 11:36AM - 11:48AM |
M2.00005: Cuprate superconductors with an incomplete Fermi surface trap the magnetic flux Hyun-Tak Kim For cuprate high-$T_{\mathrm{c}}$ superconductors, the pairing symmetry of Cooper pair is still controversial and remains unsolved. This is a central issue for the mechanism of high-$T_{\mathrm{c}}$ superconductivity. For the measurements of flux quantization obtained in the YBCO-Pb corner junction [1], DC- SQUIDS [2,3,4] and in the tricrystal superconducting ring of YBCO [4-6], the results had suggested that the measured half fluxes are strong evidence of the d$x^{\mathrm{2}}$-$y^{\mathrm{2}}$ (or d) pairing symmetry. This has still an influence on the superconductor mechanism research. At this time, we feel reanalysis of the measured half-flux-quantum data, because of the unclear analysis on flux trap in the papers. The authors [1-7] also suggested that the measured half-flux quantum comes from supercurrent induced by the superconducting ring. However, we find asymmetry of the Fraunhofer diffraction pattern, an anomalous large supercurrent, anisotropy in the half-flux quantum SQUID image. These are evidence of flux trap denying the $d$-wave symmetry. For superconducting crystals with an incomplete Fermi surface, the magnetic flux penetrates through anti-node and is expelled at node and is trapped. We suggest the s-wave pairing symmetry [8]. [1] PRL 74(1995)797, [2] PRL 71(1993)2134, [3] PRL 74(1995)4523, [4] PRL 73(1994)593, [5] Rev. Mod. Phys. 72(2000)969. [6] Science 271(1996)5249), [7] Nature Physics 5, 1 (2005). [8] J. Phys. Soc. Jpn. 71 (2002) 2106. [Preview Abstract] |
Sunday, November 5, 2017 11:48AM - 12:00PM |
M2.00006: Bose metal shows no cyclotron resonance Youcheng Wang, Idan Tamir, Dan Shahar, N. P. Armitage It is observed that many thin superconducting films with not too high disorder level (generally R$_N/\Box \leq 2000 $ Ohms) placed in magnetic field show an anomalous metallic phase where the resistance is low but still finite as temperature goes to zero, which is in contradiction with conventional wisdom that Bosons can either condense or be localized in the ground state. Previous studies have found that in this phase superconducting correlations persist but there is limited theoretical understanding, and how the electrodynamics might differ from conventional metals remains unclear. Here we report in weakly disordered amorphous InO$_x$ thin films, that this ``Bose metal" metal phase possesses no cyclotron resonance and hence non-Drude electrodynamics. The absence of a finite frequency resonant mode can be associated with a vanishing downstream component of the vortex current parallel to the supercurrent and an emergent particle-hole symmetry of this anomalous metal, which establishes its non-Fermi liquid character. [Preview Abstract] |
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