Evidence for a quantum spin liquid in single-layer 1T-TaSe2

Invited

Abstract

Quantum spin liquids are a novel state of matter predicted to arise in quantum antiferromagnets where magnetic frustration or quantum fluctuations are strong enough to prevent magnetically ordered states even down to the lowest temperatures. Quantum spin liquids are believed to exist in strongly correlated Mott insulators, and are thus related to unconventional superconductivity. Much work on quantum spin liquids has focused on triangular and kagome lattices where frustration is strong. An example is the bulk Mott insulator 1T-TaS2 which has attracted attention as a quantum spin liquid candidate due to localized d-orbitals in the Ta atoms that form a triangular lattice in this material. This scenario, however, is complicated by interlayer coupling and possible different stacking orders in the bulk, thus motivating investigation into related single-layer materials.

I will discuss recent studies that we have performed on single-layer 1T-TaSe2 that provide evidence for 2D spin liquid behavior. We have characterized the electronic structure of single-layer 1T-TaSe2 (grown via molecular beam epitaxy) by means of scanning tunneling microscopy/spectroscopy (STM/STS), angle-resolved photoemission spectroscopy (ARPES), and first-principles calculations. We observe Mott insulating behavior in single-layer 1T-TaSe2, including novel orbital texture not seen in bulk samples. Vertical heterostructures formed by a single 1T-TaSe2 layer placed on top of metallic 1H-TaSe2 exhibit Kondo behavior, providing direct evidence for a triangular array of local magnetic moments in single-layer 1T-TaSe2. Evidence for a spin-liquid-based spinon Fermi surface is observed in both STM and ARPES measurements of single-layer 1T-TaSe2. These results will be discussed in the context of recent theoretical predictions.

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Presenters

  • Wei Ruan

    University of California, Berkeley

Authors

  • Wei Ruan

    University of California, Berkeley

  • Yi Chen

    University of California, Berkeley

  • Meng Wu

    University of California, Berkeley, Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory

  • Shujie Tang

    ALS, Lawrence Berkeley National Laboratory, Lawrance Berkeley National Laboratory, Stanford University, SIMES, Stanford University, Advanced Light Source, Lawrence Berkeley National Laboratory

  • Hyejin Ryu

    Lawrence Berkeley National Laboratory, Lawrance Berkeley National Laboratory, Lawrence Berkeley Nat. Lab

  • Hsin-Zon Tsai

    University of California, Berkeley, UC Berkeley

  • Ryan Lee

    University of California, Berkeley

  • Salman Abdul Gaffar Kahn

    University of California, Berkeley

  • Franklin Liou

    University of California, Berkeley

  • Caihong Jia

    University of California, Berkeley

  • Oliver R Albertini

    Georgetown University

  • Hongyu Xiong

    Stanford University

  • Tao Jia

    Stanford University, GLAM, Stanford University

  • Zhi Liu

    Chinese Academy of Sciences, Shanghai Institute of Microsystem and Information Technology, Shanghai Institute of Microsystem and Information Technology

  • Jonathan Sobota

    Stanford University, Department of Applied Physics, Stanford University, SLAC National Accelerator Laboratory

  • Amy Liu

    Georgetown University

  • Joel Moore

    University of California, Berkeley, Department of Physics, University of California, Berkeley, California 94720, USA, University of California, Berkeley and Lawrence Berkeley National Laboratory, Physics, University of California, Berkeley, University of California, Berkeley, and Lawrence Berkeley National Laboratory

  • Zhi-Xun Shen

    Stanford University, SLAC National Accelerator Laboratory

  • Steven G. Louie

    Physics, UC Berkeley, University of California, Berkeley, Department of Physics, University of California, Berkeley, Physics Department, UC Berkeley and Lawrence Berkeley National Lab, Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory, Physics, University of California at Berkeley, University of California at Berkeley and Lawrence Berkeley National Lab, University of California at Berkeley and Lawrence Berkeley National Laboratory, Physics, University of California, Berkeley, UC Berkeley and Lawrence Berkeley National Lab, Physics, University of California - Berkeley, Physics and Materials Sciences, University of California at Berkeley and Lawrence Berkeley National Laboratory, Lawrence Berkeley National Lab and University of California, Berkeley, University of California - Berkeley, Lawrence Berkeley National Laboratory

  • Sung-Kwan Mo

    ALS, Lawrence Berkeley National Laboratory, Lawrance Berkeley National Laboratory, Lawrence Berkeley Nat. Lab, Advanced Light Source, Lawrence Berkeley National Laboratory

  • Patrick Lee

    Massachusetts Institute of Technology, Physics, Massachusetts Institute of Technology, Department of Physics, Massachusetts Institute of Technology

  • Michael F Crommie

    Physics, UC Berkeley, University of California, Berkeley, Lawrence Berkeley National Laboratory and UC Berkeley, Department of Physics, University of California at Berkeley, Physics, University of California - Berkeley