Superfluidity of magnons in ferromagnetic films

ORAL

Abstract

The magnon Bose-Einstein condensation in Yttirum Iron Garnet films at room temperature was discovered by the M\"{u}nster experimental group (S.O. Demokritov) in $2006$. Since the magnon condensate is coherent the natural question is whether the condensate is superfluid. Though the normal magnon density exceeds the condensate density in about $100$ times, the velocity of the superfluid part is by $5$-$7$ decimal orders larger than that of the normal part at the same field gradients. Thus, the spin current is dominated by the condensate, i.e. superfluid. A deeper obstacle is that the phase trapping is inconsistent with the free motion whose phase linearly depends on coordinate. The superfluidity can start only after submission of a finite (threshold) energy to the condensate by an external source. At energy close to threshold, the phase on long intervals of length remains close to the trapped values and changes by $2\pi$ on a comparatively short intervals (phase solitons). The superfluid velocity remains almost zero between solitons and acquires finite value inside solitons. Thus, the current and number of magnons are not conserved locally transferring the spin momentum to the lattice, but they are conserved globally. All these phenomena are due to the dipolar forces.

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Authors

  • Chen Sun

    Texas A&M University

  • Harry A. Atwater

    Institute for Advanced Physics and Mathematics, Zhejiang University of Technology, Baylor University, baylor university, Lanzhou Jiaotong University, Lanzhou University, Trinity University, University of New Hampshire, Los Alamos National Lab, Southwest Research Institute, University of Texas San Antonio, Texas A&M University, Department of Physics, Texas State University, San Marcos, TX78666, None, Southern Illinois University, Carbondale, Illinois 62901, Beijing Computational Science Research Center, Beijing 100094, P.R. China, The State Key Laboratory of Quantum Optics and Quantum Optics Devices, China, COMSATS Institute of Information Technology, Islamabad, Pakistan, Lamar University, NIST, NIST Physical Measurement Laboratory,Thermodynamic Metrology Laboratory, Rice University, University of Texas at Rio Grande Valley, University of Texas at Dallas, Texas Tech University, Department of Physics and Astronomy, Texas A\&M University, Russian Quantum Center, Physics Department, International Laser Center, M.V. Lomonosov Moscow State University, Baylor University, Texas A&M University, Princeton University, Baylor University, Texas A&M University, Florida State University, Univ of Texas, Dallas, University of Texas Rio Grande Valley, University of Houston, Physics and Astronomy, Material Science and Eng,Texas A\&M University. WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, Japan, Physics and Astronomy, Texas A\&M University, Material Science and Eng., Texas A\&M University, Texas Christian University, Utaca College, University of Texas at Arlington, Angelo State University Physics & Geosciences Department, Texas State University, Universidade Federal de Viçosa, Department of Physics, Lamar University, Texas Lutheran University, University of Oklahoma, Texas A&M University, Baylor University, Princeton University, Texas A&M University, Baylor University, Institute for Quantum Science and Engineering (IQSE) and Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843-4242, Texas A\&M University, Florida A&M University, Texas A&M University, Princeton University, Baylor University, Department of Physics and Astronomy, Texas A&M University, College Station, TX, Texas A&M University and Baylor University, Abilene Christian University, Michigan State University, Argonne National Laboratory, Southern Methodist University, University of Maryland, Baltimore County, Baltimore, MD 21250, Institute for Quantum Science and Engineering, Texas A&M University 4242 TAMU College Station, Texas 77843-4242, The Institute for Quantum Science and Engineering, Texas A&M University, Southern Nazarene University, Texas A&M University, Landau Institute for Theoretical Physics, University of Cologne, Department of Physics, The University of Texas at Dallas, 800 W. Campbell Rd., Richardson, Texas 75080, USA, Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA, $^{1}$Department of Physics and Astronomy, Texas A\&M University, $^{1}$Department of Physics and Astronomy, Texas A\&M University, $^{2}$WPI-AIMR, Tohoku University, Japan, Department of Physics, Austin College, AMRIS/NHMFL, University of Florida, University of Texas Southwestern Medical Center, Mississippi State University, The Methodist Hospital System, Biophotonic Solutions, Inc., University of Texas, Austin, California Insititute of Technology

  • Harry A. Atwater

    Institute for Advanced Physics and Mathematics, Zhejiang University of Technology, Baylor University, baylor university, Lanzhou Jiaotong University, Lanzhou University, Trinity University, University of New Hampshire, Los Alamos National Lab, Southwest Research Institute, University of Texas San Antonio, Texas A&M University, Department of Physics, Texas State University, San Marcos, TX78666, None, Southern Illinois University, Carbondale, Illinois 62901, Beijing Computational Science Research Center, Beijing 100094, P.R. China, The State Key Laboratory of Quantum Optics and Quantum Optics Devices, China, COMSATS Institute of Information Technology, Islamabad, Pakistan, Lamar University, NIST, NIST Physical Measurement Laboratory,Thermodynamic Metrology Laboratory, Rice University, University of Texas at Rio Grande Valley, University of Texas at Dallas, Texas Tech University, Department of Physics and Astronomy, Texas A\&M University, Russian Quantum Center, Physics Department, International Laser Center, M.V. Lomonosov Moscow State University, Baylor University, Texas A&M University, Princeton University, Baylor University, Texas A&M University, Florida State University, Univ of Texas, Dallas, University of Texas Rio Grande Valley, University of Houston, Physics and Astronomy, Material Science and Eng,Texas A\&M University. WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, Japan, Physics and Astronomy, Texas A\&M University, Material Science and Eng., Texas A\&M University, Texas Christian University, Utaca College, University of Texas at Arlington, Angelo State University Physics & Geosciences Department, Texas State University, Universidade Federal de Viçosa, Department of Physics, Lamar University, Texas Lutheran University, University of Oklahoma, Texas A&M University, Baylor University, Princeton University, Texas A&M University, Baylor University, Institute for Quantum Science and Engineering (IQSE) and Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843-4242, Texas A\&M University, Florida A&M University, Texas A&M University, Princeton University, Baylor University, Department of Physics and Astronomy, Texas A&M University, College Station, TX, Texas A&M University and Baylor University, Abilene Christian University, Michigan State University, Argonne National Laboratory, Southern Methodist University, University of Maryland, Baltimore County, Baltimore, MD 21250, Institute for Quantum Science and Engineering, Texas A&M University 4242 TAMU College Station, Texas 77843-4242, The Institute for Quantum Science and Engineering, Texas A&M University, Southern Nazarene University, Texas A&M University, Landau Institute for Theoretical Physics, University of Cologne, Department of Physics, The University of Texas at Dallas, 800 W. Campbell Rd., Richardson, Texas 75080, USA, Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA, $^{1}$Department of Physics and Astronomy, Texas A\&M University, $^{1}$Department of Physics and Astronomy, Texas A\&M University, $^{2}$WPI-AIMR, Tohoku University, Japan, Department of Physics, Austin College, AMRIS/NHMFL, University of Florida, University of Texas Southwestern Medical Center, Mississippi State University, The Methodist Hospital System, Biophotonic Solutions, Inc., University of Texas, Austin, California Insititute of Technology