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 A54: Kitaev RuCl3 and Spin Liquid Related IridatesFocus Live
|
Hide Abstracts |
Sponsoring Units: DMP Chair: Kenneth Burch |
Monday, March 15, 2021 8:00AM - 8:36AM Live |
A54.00001: Ferromagnetic Kitaev interactions and magnetic anisotropy in alpha-RuCl3 Invited Speaker: Young-June Kim α-RuCl3 is drawing much attention as a promising candidate for the Kitaev quantum spin liquid. However, despite intensive research efforts, controversy remains about the form of the basic interactions governing the physics of this material. Even the sign of the Kitaev interaction (the bond-dependent anisotropic interaction responsible for Kitaev physics) is still under debate, with conflicting results from theoretical and experimental studies. The significance of the symmetric off-diagonal exchange interaction (referred to as the Γ term) is another contentious question. We present resonant elastic and inelastic X-ray scattering data that provide unambiguous experimental constraints to the two leading terms in the magnetic interaction Hamiltonian. We show that the Kitaev interaction (K) is ferromagnetic and that the Γ term is antiferromagnetic and comparable in size to the Kitaev interaction. Our findings also provide a natural explanation for the large anisotropy of the magnetic susceptibility in α-RuCl3 as arising from the large Γ term. |
Monday, March 15, 2021 8:36AM - 8:48AM Live |
A54.00002: Phononic Structure of Kitaev Quantum Spin Liquid Candidate Material alpha-RuCl3 part 1: experiment Sai Mu, Kiranmayi Dixit, Yongqiang Cheng, Arnab Banerjee, Tom Berlijn Understanding phonons in alpha-RuCl3 is important to analyze the controversial observation of the half-integer thermal quantum Hall effect. We investigate the phononic structure of alpha-RuCl3 via Inelastic Neutron Scattering experiments and Density Functional Theory. |
Monday, March 15, 2021 8:48AM - 9:00AM Live |
A54.00003: Phononic Structure of Kitaev Quantum Spin Liquid Candidate Material alpha-RuCl3 part 2: theory Sai Mu, Kiranmayi Dixit, Yongqiang Cheng, Arnab Banerjee, Tom Berlijn Understanding phonons in alpha-RuCl3 is important to analyze the controversial observation of the half-integer thermal quantum Hall effect. We investigate the phononic structure of alpha-RuCl3 via Inelastic Neutron Scattering experiments and Density Functional Theory. |
Monday, March 15, 2021 9:00AM - 9:36AM Live |
A54.00004: Emergence of novel magnetic quasiparticles and spin liquid physics in iridates Invited Speaker: Mark Dean The strong spin-orbit coupling and moderate electronic correlations in iridates open fascinating new routes to realizing novel magnetic states. A prime example of this is Ba4Ir3O10, which has been shown to host a spin liquid ground state, despite its apparently unfrustrated quasi-2D lattice of IrO6 trimers. Here we solve this mystery using resonant inelastic x-ray scattering (RIXS) to measure the magnetic excitation spectrum, finding that it is dominated by spinons. We interpret our result using density matrix renormalization group (DMRG) model Hamiltonian calculations and density function theory calculations of hopping. These show how spins within the trimer are effectively decoupled from the lattice via the cancelation of competing interactions to yield quasi 1D physics. |
Monday, March 15, 2021 9:36AM - 9:48AM Live |
A54.00005: X-ray Absorption Studies of Structural Distortion in Ag3LiIr2O6 Alberto De La Torre, Benjamin Zager, Faranak Bahrami, Gilberto F L Fabbris, Fazel Tafti, Kemp Plumb Strong spin orbit coupling in honeycomb iridates can give rise to Jeff=1/2 states with Kitaev interactions. This is realized in alpha-Li2IrO3 and Na2IrO3, but magnetic ordering occurs at low temperatures likely due to Heisenberg interactions. Ag3LiIr2O6 is a recently synthesized Kitaev spin liquid candidate similar to α-Li2IrO3, but with the interplanar Li replaced by Ag. Thermodynamic measurements confirmed the absence of long range order. However, the higher covalency of the Ag atoms may distort the IrO6 octahedra. Large enough distortion would mix the Jeff=1/2 and Jeff=3/2 states, invalidating the Jeff=1/2 picture. To investigate the local structure and electronic states, we carried out x-ray absorption spectroscopy measurements at the Ir L2 and L3 edges in Ag3LiIr2O6 and other iridates. The near edge structure (XANES) suggests spin orbit coupling with strength comparable to that in α-Li2IrO3 and shows signs of mixed valency. From the extended x-ray absorption fine structure (EXAFS), we extract temperature dependent Ir-O bond lengths to track distortion. These results will help determine the proximity of Ag3LiIr2O6 to the Kitaev model. |
Monday, March 15, 2021 9:48AM - 10:00AM Live |
A54.00006: Electric Field Induced Mott Insulator to Soft-Gap Transition in α-RuCl3 Jordan Frick, Samanvitha Sridhar, Shaun O'Donnell, Paul Maggard, Daniel Dougherty The Mott insulator to metal transitions have been an area of intense study in highly correlated systems for many years. Lately there has been interest transitions to other electronic phases. Here, we report new experiments that induce a transition by utilizing the high electric fields under a scanning tunneling microscope (STM) tip. We are able to reversibly control the apparent Mott gap size of α-RuCl3 in STM experiments. At high fields, we can induce a collapse of the Mott gap into a soft “power law gap” phase. We directly quantify the power law exponent characterizing the gap shape which varies from ~ 2 in the Mott Insulator phase at low fields down to less than 1 at very strong fields. These observations will be discussed in the context of the generic soft gap phenomenology in correlated materials. |
Monday, March 15, 2021 10:00AM - 10:12AM Live |
A54.00007: Time Scales of Excited State Relaxation in α-RuCl3 Observed by Time-Resolved Two Photon Photoemission Spectroscopy Daniel Nevola, Alexander W Bataller, Ankit Kumar, Samanvitha Sridhar, Jordan Frick, Shaun O'Donnell, Harald W Ade, Paul Maggard, Alexander F Kemper, Kenan Gundogdu, Daniel Dougherty The existence of long-lived hot carriers in correlated materials is significant in the search for new quantum phasescreated by external driving and is also needed to quantify the strength and nature of complex electronic interactions. We have studied the photoexcitation dynamics in a spin-orbit assisted Mott insulator α-RuCl3 using time resolved two photon photoemission spectroscopy and differential reflection spectroscopy. We find that photoexcited carriers (doublons) in the upper Hubbard band (UHB) rapidly relax to Mott-Hubbard excitons (MHE) on a time scale of less than 200 fs. Subsequently, further fast relaxation of excitons occurs with a time constant of ~ 400 fs. After this process, the population of Mott-Hubbard excitons persists for very long times of at least several hundred picoseconds in agreement with several theoretical predictions about long-lived excited states in large gap Mott insulators. |
Monday, March 15, 2021 10:12AM - 10:24AM Live |
A54.00008: Magnetoelastic coupling and effects of uniaxial strain in α-RuCl3 from first principles Kira Riedl, David Kaib, Sananda Biswas, Stephen Winter, Roser Valenti Kitaev materials are prime examples where the orbital and spin degrees of freedom can not be understood separately, and instead are formulated jointly through so-called "pseudospins". In contrast to conventional spin-lattice coupling, the spin-orbital nature of the pseudospins foreshadows a much more intricate coupling to the lattice. |
Monday, March 15, 2021 10:24AM - 10:36AM Live |
A54.00009: Probing magnetic ordered states in thin crystals of spin-orbit assisted Mott insulators using a graphene heterostructure Everardo Molina, Sara S Qubbaj, Vikram Nagarajan, Derek Bergner, Isaac Arriaga, Blake Koford, James Analytis, Claudia Ojeda-Aristizabal Spin-orbit driven Mott insulators such as sodium Iridate (Na2IrO3) and alpha-ruthenium chloride (α-RuCl3) present exciting properties thanks to a combination of electronic correlations, spin-orbit coupling, crystal field effects and a honeycomb arrangement of the Ir and Ru ions respectively. These materials are in close proximity to a Kitaev-Heisenberg system, yielding exciting ground states such as gapless spin liquids and a variety of ordered states. The insulating character Na2IrO3 and RuCl3 has limited experimental probes to those that don’t require charge transport, such as thermal Hall conductance, magnetic susceptibility or neutron scattering, with few works using electronic transport. Here, we present signature of magnetic ordered states in these materials through a van der Waals heterostructure that exploits the conducting character of graphene. |
Monday, March 15, 2021 10:36AM - 10:48AM Live |
A54.00010: X-ray scattering studies of elementary excitations of α-RuCl3 Blair Lebert, Subin Kim, Valentina Bisogni, Ignace Jarrige, Andi Barbour, Ahmet Alatas, Ayman Said, Young-June Kim We investigated the Kitaeuv quantum spin liquid candidate α-RuCl3 using resonant inelsatic x-ray scattering (RIXS) and inelastic x-ray scattering (IXS). Our room temperature M3-edge RIXS results revealed a spin-orbit exciton from which we extracted values for the spin-orbit coupling constant and trigonal distortion field energy which support the jeff = 1/2 nature of α-RuCl3 [1]. I will discuss the potential of M3-edge RIXS to study 4d transition metal systems and perspectives on low temperature measurements on α-RuCl3. Finally, I will present our IXS measurements of the dispersion of acoustic phonons in α-RuCl3 measured at 5 K. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700