Bulletin of the American Physical Society
Mid-Atlantic Section Meeting 2021
Volume 66, Number 18
Friday–Sunday, December 3–5, 2021; Rutgers University, New Brunswick, New Jersey
Session D01: Quantum Matter: Topological |
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Chair: Yi Li, Johns Hopkins University Room: 201A |
Saturday, December 4, 2021 11:15AM - 11:51AM |
D01.00001: Discrete quantum geometry and intrinsic spin Hall effect Invited Speaker: Gen Yin The topological classification of continuous manifolds in real space and reciprocal space has been extensively discussed for solid-state materials. This has led to the discoveries of many intriguing materials hosting non-trivial topological orders such as helical magnets, skyrmion magnets, Chern insulators, Z2 insulators and Weyl semimetals. However, the discrete topology and geometry in these scenarios have attracted much less attention. Here I will introduce our efforts in practicing the discrete geometry and topology in solid-state physics. Such discrete perspective not only refreshes our conventional understanding, but it also resolves many difficulties encountered by their continuous counterparts. In particular I will discuss (i) the topological transition of spin textures defined on a discrete lattice, and (ii) the geometry and the topology of gapless topological materials by considering the Fermi surface as a 3D quantum manifold. [Preview Abstract] |
Saturday, December 4, 2021 11:51AM - 12:27PM |
D01.00002: Electronic Correlations and Semi-Dirac Points in Nodal-line Semimetals Invited Speaker: Yinming Shao Dirac fermions with highly-dispersive linear bands are usually considered weakly correlated, due to relatively large bandwidths (W) compared to Coulomb interactions (U). With the discovery of nodal-line semimetals, the notion of Dirac point has been extended to lines and loops in the momentum space [1]. The anisotropy associated with nodal-line structure gives rise to greatly reduced kinetic energy along the line. However, experimental evidence for anticipated enhanced correlations in nodal-line semimetals is sparse. Here we report on prominent correlation effects in a nodal-line semimetal compound ZrSiSe [2] through a combination of optical spectroscopy and density-functional-theory calculations. We observed two fundamental spectroscopic hallmarks of electronic correlations: strong reduction (1/3) of the free carrier Drude weight and of the Fermi velocity compared to predictions of density functional band theory. The renormalization of Fermi velocity can be further controlled with external magnetic field. Finally, I will discuss the discovery of gapless semi-Dirac points in a closely related compound ZrSiS [3]. The hybrid massless and massive dispersions of the elusive semi-Dirac points entail characteristic Landau levels that scale with the magnetic field as B$^{2/3}$. This unique power-law was observed in ZrSiS and the origin and implications of these semi-Dirac points will be discussed. [1] Y. Shao, Z. Sun et al, PNAS 116, 1168 (2019) [2] Y. Shao et al, Nat. Phys. 16, 6 (2020) [3] Y. Shao, S. Moon et al, (in preparation) [Preview Abstract] |
Saturday, December 4, 2021 12:27PM - 12:39PM |
D01.00003: Floquet engineering of Kitaev quantum magnets Umesh Kumar, Saikat Banerjee, Shi-Zeng Lin In recent years, there has been an intense search for materials realizing the Kitaev quantum spin liquid model. A number of edge-shared compounds with strong spin-orbit coupling, such as RuCl$_3$ and iridates, have been proposed to realize this model. Nevertheless, an effective spin Hamiltonian derived from the microscopic model relevant to these compounds generally contains terms that are antagonistic toward the quantum spin liquid. This is consistent with the fact the zero magnetic field ground state of these materials is generally magnetically ordered. It is a pressing issue to identify protocols to drive the system to the limit of the Kitaev quantum spin model. In this work, we propose Floquet engineering of these Kitaev quantum magnets by coupling materials to a circularly polarized laser. We demonstrate that all the magnetic interactions can be tuned in situ by the amplitude and frequency of the laser, hence providing a route to stabilize the Kitaev quantum spin liquid phase. [Preview Abstract] |
Saturday, December 4, 2021 12:39PM - 12:51PM |
D01.00004: Effect of Kondo-lattice coherence on the phononic and electronic excitations of CeCoIn$_{5}$ Mai Ye, Hsiang-Hsi Kung, Priscila Rosa, Eric Bauer, Kristjan Haule, Girsh Blumberg Heavy fermion metal CeCoIn$_{5}$ has a coherence temperature T*$=$45K, below which individual Kondo singlets evolve into a coherent Kondo lattice [P. Coleman, \textit{Introduction to Many-Body Physics} (Cambridge University Press, 2015)]. We study the phononic and electronic excitations of this compound by inelastic light scattering. Two optical phonon modes exhibit anomalies in their temperature dependence of frequency and linewidth below T*. Such anomalous behaviors result from developing coherent spectral weight at the Fermi level and reducing electron-phonon scattering rate. Moreover, below T* the B$_{2g}$-symmetry electronic excitations are suppressed up to 50cm$^{-1}$; the suppressed Raman response follows a cubic power law. These results support T* as the characteristic temperature marking the development of Kondo-lattice coherence. [Preview Abstract] |
Saturday, December 4, 2021 12:51PM - 1:03PM |
D01.00005: Wave and particle interaction dynamics Raghvendra Singh The outcome of a particle and wave interaction is decided by the value of the phase velocity Vp of the wave, dependent over the components of wave vector k through the following relation Vp(x,y,z)= angular frequency/k(x,y,z) < c ,momentum gain in direction perpendicular to wave vector component occurs. Vp(x,y,z)= angular frequency/k(x,y,z) > c , potential energy of the particle increases in direction perpendicular to the wave vector component. The phase velocity and in turn the outcome of the interaction is affected by the Doppler effect relation apparent angular velocity= (angular velocity +- k(x,y,z).u)/sqrt(1-(u/c)sqr) [Preview Abstract] |
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