Report

New paradigms for RIXS: 30meV resolution, and reading the quantum interference pattern L. Andrew Wray Advanced Light Source, Lawrence Berkeley National Laboratory 8/14/2013 IXS 2013 1 Collaborators LBNL Princeton University APS Zahid Hussain Yi-De Chuang Jonathan Denlinger Shih-Wen Huang Wanli Yang Ruimin Qiao Elke Arenholz M. Zahid Hasan Yuqi Xia Su-Yang Xu Nasser Alidoust Madhab Neupane Yuri Shvyd’ko SPring-8 Special thanks to UC Berkeley Z. Q. Qiu Jia Li R. Ramesh Jian Liu 8/14/2013 K. Ishii K. Ikeuchi BNL Ignace Jarrige Jinsheng Wen Zhijun Xu Genda Gu IXS 2013 Harvard University Charles Mathy AIST Hiroshi Eisaki Takami Tohyama Kenji Tsutsui R. Eder K. Wohlfeld Dung-Hai Lee Ronny Thomale Suman Hossain Sujoy Roy Padraic Shafer 2 Talk outline 1. Introduction 2. RIXS at high resolution: dd modes in CoO • “pseudo-anti-Stokes” radiation How does high resolution change what you can study with RIXS? • beyond the atomic multiplet 3. Quantum interference in RIXS spectra • 2-slit interference in cuprates • transforming into the time domain Where does quantum interference fit into RIXS analysis and simulation? •interference in arbitrary experimental spectra 4. Future directions: into the time domain! • A non-Kramers-Heisenberg calculation • New physics with ultrashort pulses • A momentum-resolved thermometer 8/14/2013 IXS 2013 3 ALS MERLIN beamline (4.0.3) RIXS at hv~40-120eV >~10meV RIXS resolution Polarization control ARPES at hv~14-120eV 8/14/2013 IXS 2013 4 RIXS at the M-edge SrCuO 2 M2,3: 3p½3d (Mn 47eV to Cu 77eV) 8/14/2013 IXS 2013 5 2 RIXS at high resolution dd modes in CoO t2g-eg dd mode eg t2g 200meV resolution dd mode 30meV resolution Temperature dependence from “any old excitation” Temperature dependence in a large spin 3D AF Mott insulator LSMO MI transition K. Ishii, PRB 2004 C. Monney, PRL 2013 Inter-site ZRS in quasi-0D The observation of effects like this is of existential importance for future pumpprobe time resolved RIXS 8/14/2013 IXS 2013 7 Pseudo-anti-Stokes pAS will instantly show where the energy is in pump-probe RIXS (AS will show where energy is after 1-2 scattering events) CoO AS states: 20meV: spin 38meV: spin-orbit 47meV: mixed Wray et al., Phys. Rev. B 88, 035105 (2013) 8/14/2013 IXS 2013 8 Shaking up the neighbors Model vs. Data 12 states/Co atom from 0-150meV Poisson AM calc Wray et al., Phys. Rev. B 88, 035105 (2013) 8/14/2013 IXS 2013 9 Mini-Summary RIXS at high resolution: • Observed “final state shake-up” excitations • Identified a likely role of electronic instabilities • First identification of “pseudo-anti-Stokes” • Will be an important q-independent signal in the time domain • Just one of many kinds of temperature dependence yet to be seen in RIXS 8/14/2013 IXS 2013 10 3 Quantum interference in RIXS spectra When a particle follows two different paths that arrive at the same place, at the same time Cuprate orbitons (SrCuO2) RIXS with just two core hole symmetries! You don’t need a ‘real’ AM calculation to understand cuprate RIXS: see Sala et al., New J. Phys. 13, 043026 (2011) 8/14/2013 IXS 2013 12 Transforming to the time domain Knowing amplitudes and phases lets you take Kramers-Heisenberg into the time domain! 8/14/2013 IXS 2013 RIXS with a 100as X-ray pulse: 13 Direct, indirect and elastic scattering SIAM Charge Transfer (NiO) ~0.2fs~1/ESOC See definitions in L. Ament review [RMP 83, 705 (2011)] 8/14/2013 IXS 2013 14 Quantum interference in complex spectra 8/14/2013 IXS 2013 15 Future directions into the time domain! Have you ever seen the momentum-vs-energy dispersion relation of a Cooper pair? RIXS gives information other spectroscopies are blind to RIXS with sub-fs pulses and time-resolved (pump-probe) capabilities will take X-ray science to new places 4 Self consistent lifetime correction (SCLC) SCLC(1): the natural answer for Kramers-Heisenberg SCLC(∞): the non-perturbative answer for a Hamiltonian K. Okada, A. Kotani, H. Ogasawara, Y. Seino, B. T. Thole, PRB 47, 6203 (1993); L. A. Wray et al., PRB 86, 195130 (2012). 8/14/2013 IXS 2013 17 Beyond Kramers-Heisenberg Another way to get a coherent core hole is to use a coherent, sub-femtosecond X-ray pulse. 8/14/2013 IXS 2013 18 Changing the core hole clock 2π/4eV=1fs L-edge Γtot (eV) 2.5 2 SCLC(∞) A KH 1.5 1 B 0 1 Time (fs) 2 Core hole decay is ~20% faster on a small time scale, during overlap with the 100as incident pulse. 8/14/2013 Same effect at the L- and K- edges! IXS 2013 19 Tracking energy in time and momentum pAS will instantly show where the energy is in pump-probe RIXS (AS will show where energy is after 1-2 scattering events) CoO AS states: 20meV: spin 38meV: spin-orbit 47meV: mixed Wray et al., Phys. Rev. B 88, 035105 (2013) 8/14/2013 IXS 2013 20 K Excitation Mechanisms 1. Atomic monopole shake-up Features: 1. Broad Q-dependence 2. Large resolving power L Excitation Mechanisms 1. Atomic multipole 2. Intersite/intraband monopole Features: 1. High throughput! 2. Weak elastic line! Now M Excitation Mechanisms 1. Strong atomic multipole 2. 10-30meV resolution: •Final state shake-up •T-dependence Features: Strong quantum interference Surface sensitivity to several unit cells Near Future Resolution similar to kBT! Resolution similar to ARPES • resolving electronic superstructure and susceptibility features Flux δE~5meV Laser coherence ? A cleaner elastic tail? Summary Color code RIXS at high resolution: • Observed temperature dependence in a simple orbiton black: M only blue: M, L and K! • First observation of “pseudo-anti-Stokes” radiation • Identified many-body spectral structure in simple orbitons Quantum interference • Fitted phase information from 2-slit interference in cuprates • Experimental RIXS data transformed into the time domain for the first time • Introduced ζ function to identify interference in arbitrary experimental spectra • QI in core hole decay improves multiplet and ultrafast simulations 8/14/2013 IXS 2013 22 23 M vs L vs K M Fast resonance processes Elastic Fano effect 1/q~20nm Best current resolution (10meV) L • 1/q~10nm • Best flux • Large spin-orbit coupling gives strong spin cross section K 1/q<< lattice constant 24 Energy resolution and the time scale of dynamics Energy resolution sets the observable time scale. With 200meV resolution, you have ~3fs. With 20meV resolution, you have ~30fs Low energy resolution: local physics High energy resolution: less local physics Excitations that take a long time to emerge can only be studied with high resolution 8/14/2013 IXS 2013 25 26 Fano tails 8/14/2013 IXS 2013 27 The dynamics of RIXS “What is the RIXS spectral function?” RIXS reveals a spectral decomposition of the many-body quantum state in the time window of core hole decay. Kramers-Heisenberg equation 8/14/2013 IXS 2013 28 When is a core hole not a core hole? Ni orbitals in NiO 9 Electron probability density 8 2p 7 6 5 4 3s 3 3p 2 3d 1 0 0 0.5 1 1.5 Radial distance (Angstroms) 8/14/2013 IXS 2013 29