Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session E48: Superconductivity: Spin Properties (NMR, NQR, neutron scattering, etc.)Live
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Sponsoring Units: DCMP Chair: Hyowon Park, University of Illinois at Chicago |
Tuesday, March 16, 2021 8:00AM - 8:12AM Live |
E48.00001: An alternate way to calculate magnetic resonance for nuclei of arbitrary spin values ZHICHEN LIU, Sunghyun Kim, Richard Klemm Although most textbooks only treat the magnetic resonance for spin ½ particles, which applies equally well for electron paramagnetic resonance and for magnetic resonance of spin ½ nuclei, in his 1966 book, Gottfried solved the Schrödinger equation for a general spin s particle in both a constant B0 and a perpendicular oscillating magnetic field B⊥cos(ωt) by transforming to a rotating reference frame. Here we provide a simpler procedure that extends the simpler solution for spin ½ particles to higher spin states. We first transform the amplitudes of the components of the spin vector to effective remove the time dependence of the effective Hamiltonian. Then, we diagonalize that effective Hamiltonian by a unitary transformation that changes the basis of the spin vector. Taking the time derivative of that Schrödinger equation then leads to a second order differential equation for each vector component, each equation of which has the form of a classical harmonic oscillator. The eigenvalues, eigenvectors, and resonance frequencies for each spin state can thereby be calculated precisely, and the eigenvalues and resonance frequencies follow a simple pattern arbitrary spin s. We will compare our results with those of Gottfried for s values up to 3. |
Tuesday, March 16, 2021 8:12AM - 8:24AM Live |
E48.00002: The adiabatic approximation for magnetic resonance of spin 1 and 3/2 nuclei Sunghyun Kim, ZHICHEN LIU, Richard Klemm The spin state of particles evolving in time during nuclear magnetic resonance (NMR) experiments is complex, because it involves both the magnitude and frequency of the applied magnetic field B(t)=B0z+B1[xcos(wt)+ysin(wt)]. Despite the complexity, the importance of understanding the spin properties of nuclei has been increasing, especially in order to characterize the pair spin state of exotic superconductors. Michael Berry in 1984 simplified the spin ½ problem in the adiabatic approximation for sufficiently low w values. However, to our knowledge, this has not previously been done for higher spin values. We have studied both the adiabatic and non-adiabatic limits for the magnetic resonance of spin 1 and 3/2 nuclei. These approximations should be useful for the interpretation of NMR experiments, especially those involving the Knight shift in superconductors. |
Tuesday, March 16, 2021 8:24AM - 8:36AM Live |
E48.00003: Paramagnons and high-temperature superconductivity in mercury-based cuprates Lichen Wang, Guanhong He, Zichen Yang, Mirian Garcia-Fernnandez, Abhishek Nag, Ke-jin Zhou, Matteo Minola, Matthieu Le Tacon, Bernhard Keimer, Yingying Peng, Yuan Li High-temperature superconductivity in the cuprates is realized upon doping antiferromagnetic parent compounds, in which spin excitations have a bandwidth of a few hundred meV. At such high energies, paramagnons and two-magnon excitations are known to persist well into and beyond the superconducting doping range [1,2,3], but it remains unclear to what extent they contribute to Cooper pairing [4] or how the magnetic and superconducting energy scales are related to each other. We have used resonant inelastic photon (Raman, X-ray) scattering to study the first two members of the Hg-family of cuprates, HgBa2CuO4+d and HgBa2CaCu2O6+d, which have nearly identical crystal structure in the charge-reservoir layers but different electronic environment in the quintessential Cu-O layers. We find that the latter compound, which has higher Tc and larger superconducting gap, also has considerably higher magnetic excitation energies. |
Tuesday, March 16, 2021 8:36AM - 8:48AM Live |
E48.00004: Manipulation of the time-reversal symmetry breaking superconductivity in Sr2RuO4 by uniaxial stress Shreenanda Ghosh, Vadim Grinenko, Rajib Sarkar, Felix Bruckner, Jean-Christophe Orain, Artem Nikitin, Joonbum Park, Mark E Barber, Naoki Kikugawa, Jake Bobowski, Dmitry Sokolov, YOSHITERU Maeno, Andrew P. Mackenzie, Hubertus Luetkens, Clifford W Hicks, Hans-Henning Klauss
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Tuesday, March 16, 2021 8:48AM - 9:00AM Live |
E48.00005: Superconductivity-induced change in magnetic anisotropy in epitaxial ferromagnet-superconductor hybrids with spin-orbit interaction César González-Ruano, Diego Caso, Coriolan Tiusan, Michel Hehn, Farkhad G Aliev Unlike the common expectation that superconducting spintronics and long-range triplet (LRT) proximity effects require complex ferromagnetic multilayers, noncollinear magnetization or half-metals, we propose a platform compatible with commercial spintronics. We have experimentally demonstrated that interfacial spin-orbit coupling (SOC) and symmetry-filtering in all-epitaxial V/MgO/Fe junctions, cooled below the critical temperature of vanadium, provide a thousand-fold increase in tunneling anisotropic magnetoresistance, supporting the LRT formation [1]. Here we report the converse effect: transformation of the magnetocrystalline anisotropy of a Fe(001) layer driven by the superconductivity of vanadium through a spin-orbit coupled MgO interface [2]. We attribute this to an additional contribution to the free energy of the ferromagnet arising from the controlled generation of triplet Cooper pairs, which depends on the relative angle between the exchange field of the ferromagnet and the spin-orbit field. This observation offers the ability to tune magnetic anisotropies using superconductivity - a key step in designing future cryogenic magnetic memories. [1] I. Martínez et al; Phys. Rev. Appl. 13, 014030 (2020); [2] C. González-Ruano et al; Phys. Rev. B, 020405(R) (2020). |
Tuesday, March 16, 2021 9:00AM - 9:12AM Live |
E48.00006: Competition between superconductivity and antiferromagnetic glass freezing in the pseudogap regime of La1.8-xEu0.2SrxCuO4 Anne Missiaen, Marc-Henri Julien, David LeBoeuf, Hadrien Mayaffre, Sunseng Pyon, Tomohiro Takayama, Hidenori Takagi A. Missiaen, H. Mayaffre, D. LeBoeuf, M.-H. Julien, Laboratoire des Champs Magnétiques Intenses, Grenoble, France |
Tuesday, March 16, 2021 9:12AM - 9:24AM Live |
E48.00007: Dynamical torques from Shiba states in s-wave superconductors Archana Mishra, So Takei, Pascal Simon, Mircea Trif Magnetic impurities inserted in a s-wave superconductor give rise to spin-polarized in-gap states called Shiba states. We study the back-action of these induced states on the dynamics of the classical moments. We show that the Shiba state pertains to both reactive and dissipative torques acting on the precessing classical spin that can be detected through ferromagnetic resonance measurements. |
Tuesday, March 16, 2021 9:24AM - 9:36AM Live |
E48.00008: Effect of Lead Doping on Inversion Symmetry Breaking in Cuprates Kayla Currier, Chiu-Yun Lin, Kenneth Gotlieb, Chris Jozwiak, Koshi Kurashima, Hiroshi Eisaki, Alessandra Lanzara The CuO2 planes of high-temperature cuprate superconductors have long been the focus of theoretical models, with less importance places on out-of-plane characteristics, due to them being the known source of superconductive states. However, to explain the helical spin texture found in Bi-based cuprates, out-of-plane characteristics must be considered. It is known that breaking of local inversion symmetry can create an out- of-plane electric field in cuprates. We focus on measuring the effect of the electric field that arises due to the incommensurate modulation on the spin polarization of Bi2Sr2CaCu2O8+δ (Bi2212). We show how the momentum-dependent spin polarization is modified through the addition of Pb dopants which decrease the incommensurate modulation. Our results give a clue to the complex interplay of spin orbit coupling and lattice characteristics. |
Tuesday, March 16, 2021 9:36AM - 9:48AM Live |
E48.00009: LaNiGa2 Phurba Sherpa, Nicholas Curro, Igor Vinograd, Valentin Taufour, Jackson Badger
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Tuesday, March 16, 2021 9:48AM - 10:00AM Live |
E48.00010: Incommensurate Spin Fluctuations in the Spin-triplet Superconductor Candidate UTe2 Chunruo Duan, Kalyan Sasmal, Jian-Xin Zhu, Andrey Podlesnyak, M Brian Maple, Qimiao Si, Pengcheng Dai Spin-triplet superconductors are of extensive current interest because they can host topological state and Majorana ferimons important for quantum computation. The uranium based heavy-fermion superconductor UTe2 has been argued as a spin-triplet superconductor similar to UGe2, URhGe, and UCoGe, where the superconducting phase is near (or coexists with) a ferromagnetic (FM) instability and spin-triplet electron pairing is driven by FM spin fluctuations. Here we use neutron scattering to show that although UTe2 exhibits no static magnetic order down to 0.3 K, its magnetism in the (0 K L) plane is dominated by incommensurate spin fluctuations near antiferromagnetic (AFM) ordering wave vector and extends to at least 2.6 meV. We are able to understand the dominant incommensurate spin fluctuations of UTe2 in terms of its electronic structure calculated using a combined density functional and dynamic mean field theory. |
Tuesday, March 16, 2021 10:00AM - 10:12AM Live |
E48.00011: Interfacial Spin Structure and Spin-Triplet Superconductivity in Magnetic-Superconducting Heterostructures Sudip Pandey, Haowen Ren, Benjamin Holladay, Brian Kirby, Julie Borchers, Eric Fullerton, Sunil K Sinha Combining superconductivity with spintronics can lead to different superconducting states, which can be useful for spin transport applications. To date, the vast majority of the research on systems that exhibit evidence of spin-triplet superconductivity in hetrostructures has used transport measurements in devices. There is limited research directly probing the nature of the interface and spin structure. Here, we used polarized neutron reflectivity combined with transport measurements to probe the interplay of magnetism and superconductivity in a new spin-triplet spin valve heterostructure with epitaxial growth of Co and Ni thin films as the fixed hard magnetic layer, epitaxial NiFe as the soft magnetic layer, and Nb as the superconductor. Magnetic states of each magnetic layer have been studied using a polarized beam reflectometer. By varying the thickness of the free magnetic layer and the angle of external field, we were able to operate on and off state of the spin-triplet spin valve. Our magnetic heterostructure shows a change in superconducting critical temperature at different angles of external field depending upon the thickness of the free magnetic layer. |
Tuesday, March 16, 2021 10:12AM - 10:24AM Live |
E48.00012: Parallel Spin Stripes and Their Coexistance with Superconducting Ground States at Optimal and High Doping in La$_{1.6-x}$Nd$_{0.4}$Sr$_x$CuO$_4$ Qianli Ma, Kirrily C. Rule, Zachary Willis Cronkwright, Mirela Dragomir, gabrielle mitchell, Evan Smith, Songxue Chi, Alexander Kolesnikov, Matthew Brandon Stone, Bruce Gaulin Quasi 2d quantum magnetism is clearly highly correlated with superconducting ground states. 3d, commensurate long range magnetic order quickly evolves to quasi-two dimensional, incommensurate correlations on doping with mobile holes, and superconducting ground states follow for x as small as 0.05 in the LSCO/LBCO family of superconductors. It has been known that superconducting ground states in these systems is coincident with a rotation of the incommensurate spin order from ``diagonal stripes" to ``parallel stripes". However, little is known about the spin correlations at optimal and high doping levels close to the end of superconductivity. Here we present new elastic and inelastic neutron scattering measurements on single crystals of La$_{1.6-x}$Nd$_{0.4}$Sr$_x$CuO$_4$ with x = 0.125, 0.19, 0.24 and 0.26, and show that 2d, quasi-static, parallel spin stripes are observed to onset at temperatures such that the parallel spin stripe phase envelopes all superconducting ground states in this system. The elastic order parameter for x = 0.19 also shows plateau behavior coincident with the onset of superconductivity. This set of observations assert the foundational role played by two dimensional parallel spin stripe order and fluctuations in High T$_c$ cuprate superconductivity. |
Tuesday, March 16, 2021 10:24AM - 10:36AM Live |
E48.00013: Studies of the Non-Centrosymmetric Superconductor ThIrSi using 29Si NMR Seth Blackwell, Frederico Benedetto Santos, Priscila Rosa, Sean Thomas, Eric D Bauer, Joe Thompson, Filip Ronning Non-centrosymmetric superconductors have stirred interest in the last number of years due to their unique characteristics. Broken inversion symmetry combined with spin-orbit coupling breaks the spin degeneracy of the Fermi surface, and allows for mixed parity superconductivity. ThIrSi possesses a non-centrosymmetric structure and demonstrates a superconducting transition temperature of 6.4K, higher than its analog compounds ThCoSi, ThNiSi, and ThPtSi. Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for condensed matter systems, primarily through measurements of the spin-lattice relaxation T1 and the Knight shift. In superconductors, NMR is particularly useful to determine the nature of the superconducting gap as well as provide evidence for spin-triplet superconductivity. We discuss our NMR results on the superconductor ThIrSi by measuring the 29Si spin-1/2 resonance. |
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