Spin-dependent transport phenomena in strongly spin-orbit coupled mesoscopic systems: spin Hall effect and Aharonov-Casher Hong Kong, August 17 th 2005.

Slides:



Advertisements
Similar presentations
Topological Insulators
Advertisements

Multisubband Monte Carlo simulations for p-MOSFETs David Esseni DIEGM, University of Udine (Italy) Many thanks to: M.De Michielis, P.Palestri, L.Lucci,
Spintronics with topological insulator Takehito Yokoyama, Yukio Tanaka *, and Naoto Nagaosa Department of Applied Physics, University of Tokyo, Japan *
New developments in the AHE: New developments in the AHE: phenomenological regime, unified linear theories, and a new member of the spintronic Hall family.
JAIRO SINOVA Research fueled by: New Horizons in Condensed Matter Physics Aspen Center for Physics February 4 th 2008 Theory challenges of semiconducting.
Topics in Condensed Matter Physics Lecture Course for graduate students CFIF/Dep. Física Spin-dependent transport theory Vitalii Dugaev Winter semester:
Spintronics: How spin can act on charge carriers and vice versa Tomas Jungwirth University of Nottingham Institute of Physics Prague.
Spintronics: How spin can act on charge carriers and vice versa Tomas Jungwirth University of Nottingham Institute of Physics Prague.
Quantum anomalous Hall effect (QAHE) and the quantum spin Hall effect (QSHE) Shoucheng Zhang, Stanford University Les Houches, June 2006.
The quantum AHE and the SHE The persistent spin helix
The Persistent Spin Helix Shou-Cheng Zhang, Stanford University Banff, Aug 2006.
Spin-orbit effects in semiconductor quantum dots Departament de Física, Universitat de les Illes Balears Institut Mediterrani d’Estudis Avançats IMEDEA.
SPIN-HALL EFFECT a new adventure in condensed matter physics San Houston State University, January 22 th 2008 JAIRO SINOVA Research fueled by: NERC.
Spin transport in spin-orbit coupled bands
Hiroyuki Inoue Electric manipulation of spin relaxation in a film using spin-Hall effect K. Ando et al (PRL in press)
Research fueled by: Instituto de Ciencia de Materiales de Madrid-CSIC November 19 th, 2010 JAIRO SINOVA Texas A&M University Institute of Physics ASCR.
Spin-injection Hall effect Spin-injection Hall effect: A new member of the spintronic Hall family Institute of Physics of the Academy of Science of the.
Spin Injection Hall Effect: a new member of the spintronic Hall family and its implications in nano-spintronics Research fueled by: Optical Spintronics.
Research fueled by: University of Utah November 9 th, 2010 JAIRO SINOVA Texas A&M University Institute of Physics ASCR Echoes of special relativity in.
JAIRO SINOVA Research fueled by: NERC ICNM 2007, Istanbul, Turkey July 25 th 2007 Anomalous and Spin-Hall effects in mesoscopic systems.
Research fueled by: Freie Universitaet Berlin April 12 th, 2010 JAIRO SINOVA Texas A&M University Institute of Physics ASCR New paradigms in spin-charge.
Optical study of Spintronics in III-V semiconductors
Experimental observation of the Spin-Hall Effect in InGaN/GaN superlattices Student : Hsiu-Ju, Chang Advisor : Yang Fang, Chen.
Spin Hall Effect induced by resonant scattering on impurities in metals Peter M Levy New York University In collaboration with Albert Fert Unite Mixte.
Spin Injection Hall Effect: a new member of the spintronic Hall family Symposium Spin Manipulation in Solid State Systems Würzburg, October 8th - 9th,
Research fueled by: JAIRO SINOVA Texas A&M University Institute of Physics ASCR Hitachi Cambridge Jörg Wunderlich, A. Irvine, et al Institute of Physics.
Research fueled by: JAIRO SINOVA Texas A&M University Institute of Physics ASCR Hitachi Cambridge Jörg Wunderlich, A. Irvine, et al Institute of Physics.
1 Motivation: Embracing Quantum Mechanics Feature Size Transistor Density Chip Size Transistors/Chip Clock Frequency Power Dissipation Fab Cost WW IC Revenue.
Spin-injection Hall effect Spin-injection Hall effect: A new member of the spintronic Hall family Computational Magnetism and Spintronics International.
Research fueled by: Ohio State University February 9 th, 2010 JAIRO SINOVA Texas A&M University Institute of Physics ASCR Exploiting the echoes of special.
Berry phase effects on Electrons
Research fueled by: Forschungszentrum Jülich November 11 th, 2009 JAIRO SINOVA Texas A&M University Institute of Physics ASCR Hitachi Cambridge Joerg W.
New spintronic device concept using spin injection Hall effect: a new member of the spintronic Hall family JAIRO SINOVA Texas A&M University Institute.
Anomalous Hall transport in metallic spin-orbit coupled systems November 11 th 2008 JAIRO SINOVA Texas A&M University Institute of Physics ASCR Research.
Dissipationless quantum spin current at room temperature Shoucheng Zhang (Stanford University) Collaborators: Shuichi Murakami, Naoto Nagaosa (University.
Topological Aspects of the Spin Hall Effect Yong-Shi Wu Dept. of Physics, University of Utah Collaborators: Xiao-Liang Qi and Shou-Cheng Zhang (XXIII International.
Optical Properties of Ga 1-x Mn x As C. C. Chang, T. S. Lee, and Y. H. Chang Department of Physics, National Taiwan University Y. T. Liu and Y. S. Huang.
Berry Phase Effects on Bloch Electrons in Electromagnetic Fields
Spintronics Tomas Jungwirth University of Nottingham Institute of Physics ASCR, Prague.
Spin-dependent transport in the presence of spin-orbit interaction L.Y. Wang a ( 王律堯 ), C.S. Tang b and C.S. Chu a a Department of Electrophysics, NCTU.
Observation of the spin-Hall Effect Soichiro Sasaki Suzuki-Kusakabe Lab. Graduate School of Engineering Science Osaka University M1 Colloquium.
Nripen Dhar p Outlines of Presentation Discovery Principles Importance Existing measurement system Applications New Discoveries 2.
Berry Phase Effects on Electronic Properties
Research fueled by: 8th International Workshop on Nanomagnetism & Superconductivity Coma-ruga July 2 nd, 2012 Expecting the unexpected in the spin Hall.
Ferromagnetic and non-magnetic spintronic devices based on spin-orbit coupling Tomas Jungwirth Institute of Physics ASCR Alexander Shick University of.
The spin Hall effect Shoucheng Zhang (Stanford University) Collaborators: Shuichi Murakami, Naoto Nagaosa (University of Tokyo) Andrei Bernevig, Taylor.
Research fueled by: Frontiers in Materials: Spintronics Strasboug, France May 13 th, 2012 Expecting the unexpected in the spin Hall effect: from fundamental.
Quantum pumping and rectification effects in interacting quantum dots Francesco Romeo In collaboration with : Dr Roberta Citro Prof. Maria Marinaro University.
Spin Hall effect J. Wunderlich(1), B. Kästner(1,2), J. Sinova (3), T. Jungwirth (4,5) Hitachi Cambridge Laboratory, UK National Physical Laboratory, UK.
Detection of current induced Spin polarization with a co-planar spin LED J. Wunderlich (1), B. Kästner (1,2), J. Sinova (3), T. Jungwirth (4,5) (1)Hitachi.
Research fueled by: International Symposium High Performance Computing in Nano-Spintronics Hamburg, November 30 th, 2011 Transport theory and simulations.
The Helical Luttinger Liquid and the Edge of Quantum Spin Hall Systems
Microscopic theory of spin transport
2D Topological insulator in HgTe quantum wells Z.D. Kvon Institute of Semiconductor Physics, Novosibirsk, Russia 1. Introduction. HgTe quantum wells. 2.
Topological Insulators Effects of spin on transport of electrons in solids.
Hall effects and weak localization in strong SO coupled systems : merging Keldysh, Kubo, and Boltzmann approaches via the chiral basis. SPIE, San Diego,
Spin-orbit interaction in semiconductor quantum dots systems
SemiSpinNe t Research fueled by: ASRC Workshop on Magnetic Materials and Nanostructures Tokai, Japan January 10 th, 2012 Vivek Amin, JAIRO SINOVA Texas.
German Physical Society Meeting March 26 th, 2012 Berlin, Germany Research fueled by: JAIRO SINOVA Texas A&M University Institute of Physics ASCR UCLA.
Berry Phase and Anomalous Hall Effect Qian Niu University of Texas at Austin Supported by DOE-NSET NSF-Focused Research Group NSF-PHY Welch Foundation.
Extraordinary magnetoresistance in GaMnAs ohmic and Coulomb blockade devices Tomas Jungwirth University of Nottingham Bryan Gallagher, Tom Foxon, Richard.
Quantum spin Hall effect Shoucheng Zhang (Stanford University) Collaborators: Andrei Bernevig, Congjun Wu (Stanford) Xiaoliang Qi (Tsinghua), Yongshi Wu.
Topological Insulators
Anomalous Hall effects :
Qian Niu 牛谦 University of Texas at Austin 北京大学
Spin-orbit interaction in a dual gated InAs/GaSb quantum well
Gauge structure and effective dynamics in semiconductor energy bands
Lecture 2:
Review of semiconductor physics
Presentation transcript:

Spin-dependent transport phenomena in strongly spin-orbit coupled mesoscopic systems: spin Hall effect and Aharonov-Casher Hong Kong, August 17 th 2005 JAIRO SINOVA Collaborators supported by: Collaborators: Allan MacDonald, Dimitri Culcer, Ewelina Hankeiwc, Qian Niu, Kentaro Nomura, Nikolai Sinitsyn, Laurens Molenkamp, Hartmut Buhmann, Charlie Becker, Volker Daumer, Yongshen Gui Matthias König, Jian Liu, Markus Schäfer, Joerg Wunderlich, Bernd Kästner, Tomas Jungwirth, Branislav Nikolic, Satofumi Souma, Liviu Zarbo, Mario Borunda

OUTLINE Spin dependent transport in SO coupled systems: Das-Datta transistor paradigm Spin dependent transport in SO coupled systems: Das-Datta transistor paradigm Spin-Hall effect Spin-Hall effect Basic pheonemonlogy Basic pheonemonlogy Some settled issues: mini-workshop on spin-Hall effect Some settled issues: mini-workshop on spin-Hall effect Spin Hall effect in the mesoscopic regime Spin Hall effect in the mesoscopic regime Why study the mesoscopic regime Why study the mesoscopic regime Transport indications of SHE in the mesoscopic regime Transport indications of SHE in the mesoscopic regime Spin accumulation in ballistic and coherent systems Spin accumulation in ballistic and coherent systems Aharonov-Casher effect in mesoscopic rings Aharonov-Casher effect in mesoscopic rings

Spin-orbit coupling interaction (one of the few echoes of relativistic physics in the solid state) Ingredients: -“Impurity” potential V(r) - Motion of an electron Produces an electric field In the rest frame of an electron the electric field generates and effective magnetic field This gives an effective interaction with the electron’s magnetic moment CONSEQUENCES If part of the full Hamiltonian quantization axis of the spin now depends on the momentum of the electron !! If treated as scattering the electron gets scattered to the left or to the right depending on its spin!!

Spin Hall effect like-spin Spin-orbit coupling “force” deflects like-spin particles I _ F SO _ _ _ V=0 non-magnetic Spin-current generation in non-magnetic systems without applying external magnetic fields Spin accumulation without charge accumulation excludes simple electrical detection Take now a PARAMAGNET instead of a FERROMAGNET: Carriers with same charge but opposite spin are deflected by the spin-orbit coupling to opposite sides. Refs: Dyakonov and Perel (71), J. E. Hirsch (99)

INTRINSIC SPIN-HALL EFFECT: INTRINSIC SPIN-HALL EFFECT: Murakami et al Science 2003 (cond-mat/ ) Sinova et al PRL 2004 (cont-mat/ ) as there is an intrinsic AHE (e.g. Diluted magnetic semiconductors), there should be an intrinsic spin-Hall effect!!! Inversion symmetry  no R-SO Broken inversion symmetry  R-SO (differences: spin is a non-conserved quantity, define spin current as the gradient term of the continuity equation. Spin-Hall conductivity: linear response of this operator) n, q n’  n, q

Disorder effects: beyond the finite lifetime approximation for Rashba 2DEG Question: Are there any other major effects beyond the finite life time broadening? Does side jump contribute significantly? Inoue, Bauer, Molenkamp PRB 04 Ladder partial sum vertex correction: Also: Mishchenko et al, PRL 04 Raimondi et al, PRB 04, Dimitrova PRB05, Loss et al, PRB 05 NOTE: the vertex corrections are zero for 3D hole systems (Murakami 04) and 2DHG (Bernevig and Zhang 05)

Experimental observations Wunderlich, Kästner, Sinova, Jungwirth, cond-mat/ PRL in press: Experimental observation of the spin-Hall effect in a two dimensional spin-orbit coupled semiconductor system Co-planar spin LED in GaAs 2D hole gas: ~1% polarization CP [%] Light frequency (eV) Kato, Myars, Gossard, Awschalom, Science Nov 04 Observation of the spin Hall effect bulk in semiconductors Local Kerr effect in n-type GaAs and InGaAs: ~0.03% polarization (weaker SO-coupling, stronger disorder)

SHE controversy Does the SHE conductivity vanish due to scattering? Seems to be the case in 2DRG+Rashba (Inoue et al 04), does not for any other system studied Dissipationless vs. dissipative transport Is the SHE non-zero in the mesoscopic regime? What is the best definition of spin-current to relate spin-conductivity to spin accumulation ……

APCTP Workshop on Semiconductor Nano-Spintronics: Spin-Hall Effect and Related Issues August 8-11, 2005 APCTP, Pohang, Korea A COMMUNITY WILLING TO WORK TOGETHER

Semantics agreement: The intrinsic contribution to the spin Hall conductivity is the the spin Hall conductivity in the limit of strong spin orbit coupling and  >>1. This is equivalent to the single bubble contribution to the Hall conductivity in the weakly scattering regime. General agreement The spin Hall conductivity in a 2DEG with Rashba coupling vanishes in the absence of a magnetic field and spin-dependent scattering. The intrinsic contribution to the spin Hall conductivity is identically cancelled by scattering (even weak scattering). This unique feature of this model can be traced back to the specific spin dynamics relating the rate of change of the spin and the spin current directly induced, forcing such a spin current to vanish in a steady non-equilibrium situation. The cancellation observed in the 2DEG Rashba model is particular to this model and in general the intrinsic and extrinsic contributions are non-zero in all the other models studied so far. In particular, the vertex corrections to the spin-Hall conductivity vanish for p-doped models.

OUTLINE Spin dependent transport in SO coupled systems: Das-Datta transistor paradigm Spin dependent transport in SO coupled systems: Das-Datta transistor paradigm Spin-Hall effect Spin-Hall effect Basic pheonemonlogy Basic pheonemonlogy Some settled issues: mini-workshop on spin-Hall effect Some settled issues: mini-workshop on spin-Hall effect Spin Hall effect in the mesoscopic regime Spin Hall effect in the mesoscopic regime Why study the mesoscopic regime Why study the mesoscopic regime Transport indications of SHE in the mesoscopic regime Transport indications of SHE in the mesoscopic regime Spin accumulation in ballistic and coherent systems Spin accumulation in ballistic and coherent systems Aharonov-Casher effect in mesoscopic rings Aharonov-Casher effect in mesoscopic rings

Non-equilibrium Green’s function formalism (Keldysh-LB) Advantages: No worries about spin-current definition. Defined in leads where SO=0 Well established formalism valid in linear and nonlinear regime Easy to see what is going on locally SHE in the mesoscopic regime

Spin Hall effect in the mesoscopic regime, simplifying the debate Hankiewicz, Molenkamp, Jungwirth, Sinova, PRB 70, (R) (2004). Also: Sheng et al, PRL 05 Nikolic et al, PRB 05 6

Actual gated H-bar sample HgTe-QW  R = 5-15 meV 5  m ohmic Contacts Gate- Contact Unfortunately the device is too large to observe coherent transport

Nikolic, Souma, Zarbo, and Sinova, PRL 05 Spin accumulation in mesoscopic systems

x100, E F =-3.8t, t so =0.1t Non-linear regime Rashba Model

OUTLINE Spin dependent transport in SO coupled systems: Das-Datta transistor paradigm Spin dependent transport in SO coupled systems: Das-Datta transistor paradigm Spin-Hall effect Spin-Hall effect Basic pheonemonlogy Basic pheonemonlogy Some settled issues: mini-workshop on spin-Hall effect Some settled issues: mini-workshop on spin-Hall effect Spin Hall effect in the mesoscopic regime Spin Hall effect in the mesoscopic regime Why study the mesoscopic regime Why study the mesoscopic regime Transport indications of SHE in the mesoscopic regime Transport indications of SHE in the mesoscopic regime Spin accumulation in ballistic and coherent systems Spin accumulation in ballistic and coherent systems Aharonov-Casher effect in mesoscopic rings Aharonov-Casher effect in mesoscopic rings

HgTe Ring-Structures Three phase factors: Aharonov-Bohm Berry Aharonov-Casher

High Electron Mobility  > 3 x 10 5 cm 2 /Vsec

Rashba Effect in HgTe Rashba splitting energy 8 x 8 k  p band structure model A. Novik et al., PRB 72, (2005). Y.S. Gui et al., PRB 70, (2004).

HgTe Ring-Structures Modeling E. Hankiewicz, J. Sinova, Concentric Tight Binding Model + B-field

CONCLUSION Spin Hall effect is robust in the mesoscopic regime Spin Hall effect is robust in the mesoscopic regime Coherent transport can in principle be used as a spin injector. Coherent transport can in principle be used as a spin injector. Need to connect the two regimes (bulk, mesoscopic) Need to connect the two regimes (bulk, mesoscopic) Need a consistent spin-accumulation theory (in terms of the chiral states) Need a consistent spin-accumulation theory (in terms of the chiral states) Aharonov-Casher effect in HgTe ring nanostructure consistent with theory Aharonov-Casher effect in HgTe ring nanostructure consistent with theory

Rashba Splitting (Bychkov-Rashba) subband splitting due to macroscopic asymmetric potential spin orbit coupling in an asymetric potential  Rashba hamiltonian Rashba term  : effective mass parameter  : vector of Pauli spin matrices E : confining electric field energy dispersion in case of a hole system

Band Structure of HgTe QWs 4 nm QW 15 nm QW normal semiconductor E2 H1 H2 L1 inverted semiconductor

First Data Asymmetric HgTe-QW  R = 5-15 meV

Inverted Bandstructure type-III QW

First Data HgTe-QW  R = 5-15 meV Signal due to depletion...

Other Wafer Symmetric HgTe-QW  R = 0-5 meV Signal less than 10 -4

HgTe: Semimetal or Semiconductor D.J. Chadi et al. PRB, 3058 (1972) zero gap: fundamental gap bandstructure

Using SO: Datta-Das spin FET V - v B eff - v - v V/2

HgTe Quantum-Well wellbarrier VBO = 570 meV