Name: experimental methods for spin- and angle-resolved photoemission spectroscopy combined with polarization-variable laser
Uploaded: 2018-06-28T13:00:00.000+00:00
Duration: 9 min
Description: Watch this Scientific Journal Video about Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser at JoVE.com

福島聡豊久中山雅に感謝我々 の石田慶樹が実験のセットアップ サポートしています。感謝する資金日本学術振興会 Grantin 援助から研究 (B) プロジェクト号 26287061 を通じての若手研究 (B) プロジェクト号経由 15 K 17675。この作品も (新学術領域「トポロジカル材料科学」許可第 16 H 00979) 日本の文部科学省と日本学術振興会科研費 (補助金第 16 H 02209) によって支持された

1. サンプル マウントとインストール
<ol><li>1 × 1 × 0.5 mm のおおよそのサイズに切断した Bi2Se313の単結晶試料試料ホルダーにサンプルを接着するエポキシをスライバー ベース3の使用。</li>
	<li>試料表面にセロハン テープを貼り付けます。 メモ: スコッチ テープは、超高真空 (UHV) アトミックきれいな表面を得るためにサンプルの切断に使用されます。</li>
	<li>読み込みロックの雑誌のサンプルにサンプルをインストール、読み込みロックの圧力は 1 × 10-5 pa. より下までポンプを開始</li>
</ol>2. サンプルの切断
<ol><li>読み込みロックと超高真空準備室の超高真空バルブを開きます。</li>
	<li>リニア/回転フィードスルー ロードロック室に接続されているを使用して、ロード岩からサンプル雑誌を準備室に移動します。</li>
	<li>準備室に接続されている転送棒によって雑誌のサンプルからサンプルをピックアップします。</li>
	<li>サンプル誌に戻す負荷ロック、超高真空バルブを閉じます。</li>
	<li>準備室の圧力が 5 × 10-7 pa. を下回るまで待つ</li>
	<li>準備室で揺れのスティックを使用してセロハン テープをはがし、超高真空条件下で試料を切断します。</li>
</ol>3. サンプル測定位置に転送
<ol><li>超高真空の測定室にサンプルを転送し、測定チャンバー搭載スクリュー ドライバーによってメイン ゴニオ ステージにサンプルを修正します。</li>
	<li>測定位置にゴニオ ステージを移動し、正確に分光器の焦点にサンプル位置を移動するマイクロメータ ステージを使用します。</li>
</ol>4. 7 eV レーザー セットアップ
<ol><li>Nd:YVO4 レーザーをオンにします。 注: レーザーは、120 MHz の高繰り返し率 355 nm のレーザー光を生成します。</li>
	<li>レーザー ビーム シャッターを開き、レーザーは通過、kbbf、177 の第 2 高調波を確認 nm (6.994 eV) が生成されます。</li>
	<li>可変減衰器と 355 nm レーザーのパワーを変更することによって 7 eV レーザーのパワーを最適化します。</li>
</ol>5. 角度分解光電子分光データ集録
<ol><li>デスクトップ コンピューター上のアナライザー コントロール ソフトウェアを開きます。 注: 我々 は電子デフ付け制御 ScientaOmicron アナライザーの一般的なプログラムである「SES ソフトウェア"を使用します。</li>
	<li>... 以下のシーケンスメニューのセットアップを選択して (図 2、ステップ i.2 1) バー。</li>
	<li>光電子デフ付けフェルミ面マッピングを実行する一覧 (図 3、ステップ i.3 2) の角度分解光電子分光構成(図 3、ステップ i.3 1) と角度分解光電子分光マッピングを選択します。</li>
	<li>(図 3、ステップ i.3 3) を編集をクリックし、-12 ° から 0.5 ° (図 3のステップ i.3-4) のステップ サイズの出射角θyの 12 ° までフェルミ面マッピングを構成します。 注: 電子デフ付け半球アナライザーは、サンプル回転せずフェルミ面にマップすることが出来ます。</li>
	<li>(図 2i.2-3 の手順) を実行をクリックします。</li>
</ol>6. SARPES データ集録
<ol><li>SARPES 測定アナライザー入口スリットや絞りのサイズ (図 1) などの機械のセットアップを手動で変更します。</li>
	<li>... 以下のシーケンスメニューのセットアップを選択して (図 2、ステップ i.2 2) バー。</li>
	<li>リスト (図 4、ステップ i.4 2)、(図 4、ステップ i.4 1)構成をスピンとノーマルを選択し、 [ok] (図 4、ステップ i.4 3) をクリックします。</li>
	<li>メニュー バーおよびコントロール シータのDA30 (図 5、手順 i.5 1) を選択してください.(図 5、手順 i.5 2) DA30 角 (θx, θy) 構成の設定パネルを開きます。</li>
	<li>発光角度 (θxと θy) を選択 (-6 °、0 °) = SARPES スペクトル (図 5手順 3 i.5) を取る。</li>
	<li>特定の軸に沿って正の方向に VLEED ターゲットを磁化するバイポーラ コンデンサー銀行を制御することによって磁場を適用 (α: x y、またはz)。 注: システムでこのプロセスは [図 6 (a)] コマンド プロンプトから実行できます。</li>
	<li>強度スペクトル (図 2i.2-3 の手順) を実行をクリックします。</li>
	<li>Α に沿って負の方向に VLEED ターゲットを磁化させるし、強度スペクトルをスキャンを開始するための磁界を適用します。</li>
	<li>スピン偏極とスピン分解スペクトルを計算します。</li>
</ol>7. 光の偏波依存性をスキャン
<ol><li>7 eV レーザーの偏光をチューニングするステッピング モーターによりきめ細かい制御が λ/2-用の角度を変更します。 注: 我々 のシステムでこのプロセスは [図 6 (b)] コマンド プロンプトから実行できます。</li>
	<li>X、y 、およびz軸のスピン分解スペクトルを取る。</li>
	<li>102 ° 3 ° のステップ サイズの 0 ° から半波長板の角度を変えることで光の偏光の関数としてスピン分解スペクトルをスキャンします。</li>
</ol>

<ol>
	<li>Damascelli, A., Hussain, Z., Shen, Z. -. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Angle-resolved+photoemission+studies+of+the+cuprate+superconductors.">Angle-resolved photoemission studies of the cuprate superconductors.</a> Rev. Mod. Phys. 75 (2), 473-541 (2003).</li><li>Qiao, S., Kimura, A., Harasawa, A., Sawada, M., Chung, J. -. G., Kakizaki, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+compact+electron+spin+polarimeter+with+a+high+efficiency.">A new compact electron spin polarimeter with a high efficiency.</a> Rev. Sci. Instrum. 68 (12), 4390-4395 (1997).</li><li>Dil, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spin+and+angle+resolved+photoemission+on+non-magnetic+low-dimensional+systems.">Spin and angle resolved photoemission on non-magnetic low-dimensional systems.</a> J. Phys. Condens. Matter. 21 (40), 403001 (2009).</li><li>Hoesch, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spin-polarized+Fermi+surface+mapping.">Spin-polarized Fermi surface mapping.</a> J. Electron Spectrosc. 124 (2), 263-279 (2002).</li><li>Souma, S., Takayama, S., Sugawara, K., Sato, T., Takahashi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrahigh-resolution+spin-resolved+photoemission+spectrometer+with+a+mini+Mott+detector.">Ultrahigh-resolution spin-resolved photoemission spectrometer with a mini Mott detector.</a> Rev. Sci. Instrum. 81 (9), 096101 (2010).</li><li>Okuda, T., Kimura, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spin-+and+angle-resolved+photoemission+of+strongly+spin-orbit+coupled+systems.">Spin- and angle-resolved photoemission of strongly spin-orbit coupled systems.</a> J. Phys. Soc. Jpn. 82 (2), 021002 (2013).</li><li>Okuda, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+spin-polarized+photoemission+spectrometer+with+very+high+efficiency+and+energy+resolution.">A new spin-polarized photoemission spectrometer with very high efficiency and energy resolution.</a> Rev. Sci. Instrum. 79 (12), 123117 (2008).</li><li>Jozwiak, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high-efficiency+spin-resolved+photoemission+spectrometer+combining+time-of-flight+spectroscopy+with+exchange-scattering+polarimetry.">A high-efficiency spin-resolved photoemission spectrometer combining time-of-flight spectroscopy with exchange-scattering polarimetry.</a> Rev. Sci. Instrum. 81 (5), 053904 (2010).</li><li>Okuda, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+spin+resolved+spectroscopy+observation+machine+at+Hiroshima+Synchrotron+Radiation+Center.">Efficient spin resolved spectroscopy observation machine at Hiroshima Synchrotron Radiation Center.</a> Rev. Sci. Instrum. 82 (10), 103302 (2011).</li><li>Yaji, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-resolution+three-dimensional+spin-+and+angle-resolved+photoelectron+spectrometer+using+vacuum+ultraviolet+laser+light.">High-resolution three-dimensional spin- and angle-resolved photoelectron spectrometer using vacuum ultraviolet laser light.</a> Rev. Sci. Instrum. 87 (5), 053111 (2016).</li><li>Shimojima, T., Okazaki, K., Shin, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-temperature+and+high-energy-resolution+laser+photoemission+spectroscopy.">Low-temperature and high-energy-resolution laser photoemission spectroscopy.</a> J. Phys. Soc. Jpn. 84 (7), 072001 (2015).</li><li>Augustine, S., Mathai, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth,+morphology,+and+microindentation+analysis+of+Bi2Se3,+Bi1.8In0.2Se3,+and+Bi2Se2.8Te0.2+single+crystals.">Growth, morphology, and microindentation analysis of Bi2Se3, Bi1.8In0.2Se3, and Bi2Se2.8Te0.2 single crystals.</a> Mater. Res. Bull. 36 (13), 2251-2261 (2001).</li><li>Hasan, M. Z., Kane, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colloquium:+Topological+insulators.">Colloquium: Topological insulators.</a> Rev. Mod. Phys. 82 (4), 3045-3067 (2010).</li><li>Ando, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Topological+insulator+materials.">Topological insulator materials.</a> J. Phys. Soc. Jpn. 82 (10), 102011 (2013).</li><li>Zhang, H., Liu, C. -. X., Qi, X. -. L., Dai, X., Fang, Z., Zhang, S. -. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Topological+insulators+in+Bi2Se3,+Bi2Te3+and+Sb2Te3+with+a+single+Dirac+cone+on+the+surface.">Topological insulators in Bi2Se3, Bi2Te3 and Sb2Te3 with a single Dirac cone on the surface.</a> Nature Phys. 5 (6), 438-442 (2009).</li><li>Cao, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+the+orbital+wavefunction+of+the+surface+states+in+three-dimensional+topological+insulators.">Mapping the orbital wavefunction of the surface states in three-dimensional topological insulators.</a> Nature Phys. 9 (8), 499-504 (2013).</li><li>Zhang, H., Liu, C. -. X., Zhang, S. -. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spin-orbital+texture+in+topological+insulators.">Spin-orbital texture in topological insulators.</a> Phys. Rev. Lett. 111 (6), 066801 (2013).</li><li>Kuroda, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coherent+control+over+three-dimensional+spin-polarization+for+the+spin-orbit+coupled+surface+state+of+Bi2Se3.">Coherent control over three-dimensional spin-polarization for the spin-orbit coupled surface state of Bi2Se3.</a> Phys. Rev. B. 94 (16), 165162 (2016).</li><li>Meier, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interference+of+spin+states+in+photoemission+from+Sb/Ag(111)+surface+alloys.">Interference of spin states in photoemission from Sb/Ag(111) surface alloys.</a> J Phys-Condens Mat. 23 (7), 072207 (2011).</li><li>Dil, J. H., Meier, F., Osterwalder, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rashba-type+spin+splitting+and+spin+interference+of+the+Cu(111)+surface+state+at+room+temperature.">Rashba-type spin splitting and spin interference of the Cu(111) surface state at room temperature.</a> J Electron Spectrosc. 201, 42-46 (2015).</li><li>Yaji, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spin-dependent+quantum+interference+in+photoemission+process+from+spin-orbit+coupled+states.">Spin-dependent quantum interference in photoemission process from spin-orbit coupled states.</a> Nature Commun. 8, 14588 (2017).</li><li>Noguchi, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+mapping+of+spin+and+orbital+entangled+wave+functions+under+interband+spin-orbit+coupling+of+giant+Rashba+spin-split+surface+states.">Direct mapping of spin and orbital entangled wave functions under interband spin-orbit coupling of giant Rashba spin-split surface states.</a> Phys. Rev. B. 95 (6), 04111(R) (2017).</li></ol>

著者は、彼らは競合する金銭的な利益があることを宣言します。

角度分解光電子分光と SARPES 技術は、一般バンド マッピングとスピン検出1,2バンド電子構造を研究するために使用されています。上記これらの一般的な利点に加えてレーザー SARPES 光双極子励起の軌道選択ルールに基づくは波動関数と量子スピン干渉におけるスピン軌道結合効果を可視化する手法として用いることができます。.レーザーの偏光を?...

角度分解光電子分光 (ARPES) 法は固体状態1の準粒子バンド構造を調査する最も強力なツールの 1 つに開発しました。角度分解光電子分光の魅力的な機能のほとんどは、エネルギーと運動量空間での電子の状態を特徴付けるバンド マッピングの機能です。スピン分解 ARPES (SARPES)、ここで例えばスピン検出器を装備。モット検出器2,3はさらに、観測バンド構造4スピン性を解決することが出来ます。さらに 2 つモット検出器の組み合わせにより 3 つのディメンション4,5 のスピンの向きを取得する 1 つ、モット検出器は、2 つの軸 (xとz、またはyおよびz) とスピンを測定できる、ので.数十年、ただし、SARPES 実験被害がなかった彼らの低効率 (通常 1/10000 スピン統合角度分解光電子分光測定の比較)3,4,5,6 、7エネルギーや角解像度に限られていた。いわゆる非常に低エネルギー電子線回折 (VLEED) 検出器7,8,9交換散乱に基づく高効率スピン検出器を用いた SARPES のエネルギー分解能を増加している最近、 ,10。この器、データの品質が大幅に改善されているし、データ収集時間が短縮されています。最近では、SARPES は、スピン偏極電子状態とスピンのテクスチャ表面バンド7の結果特にスピン軌道結合効果に対処するため大きくしました。
ここでは、SARPES を用いて偏波可変真空紫外測定レーザー光 (レーザー-SARPES)、この複合技術の大きな利点を発揮します。Bi2Se3スピン軌道結合表面状態の調査を通してレーザー SARPES の 2 つの機能を提案する.まず、 s p- 双極子遷移領域における直線偏光レーザの軌道選択ルールのため-偏光が軌道対称性の異なる波動関数の固有の部分を選択的にエキサイトします。そのような軌道選択的励起はそれにより SARPES、すなわち、軌道選択的 SARPES で利用可能です。第二に、SARPES で 3次元 (3 D) スピン検出はスピン量子軸の方向を示し、直接偏光依存性の完全な情報が表示されます。このプロトコルでは、簡単に強力なスピン軌道結合効果を研究するこの最新のレーザー SARPES テクニックを実行する方法をについて説明します。
11東京大学物性研究所でレーザー SARPES システムがあります。レーザー様々 SAPRES マシンの図は図 1に示します。偏波可変 7 eV レーザー光12はサンプル表面を照らすし、サンプルから光電子が放出されます。レーザーの偏光は、MgF2- 基づく λ/2 - と波長板 λ/4 直線および円偏波を選択的に使用するによって自動的に制御されます。半球電子アナライザーは、光電子を修正し、運動エネルギー (E親族)、放出角度 (θxとθy) を分析します。光電子強度はEキン- CCD カメラによって監視されているθx画面にマップされます。この画像は、逆格子空間におけるエネルギー バンド構造に直接変換されます。
SARPES 測定の具体的な排出角度と電子アナライザーを用いて運動エネルギー光電子が 90 度光電子デフ付け 2 VLEED 型スピン検出器に導かれているし、光電子ビームは、2 つに焦点を当てています。fe (001)p(1 × 1) 薄膜の酸素によって終了の異なるターゲット。ターゲットによって反映される光電子は、各スピン検出器は、channeltron を使用して、単一チャンネル検出で検出されます。VLEED ターゲットは、互いに対して直交するジオメトリと整理されるヘルムホルツ型電気コイル磁化することができます。磁化の向きは、バイポーラ コンデンサー銀行によって制御されます。ダブル VLEED スピン検出器により、私たちは 3 つの次元での光電子スピン分極ベクトルを分析します。

<table><tbody><tr><td>DA30-L hemispherical analyzer</td><td>ScientaOmicron</td><td></td><td>http://www.scientaomicron.com/en/products/353/1170</td></tr><tr><td>Silver-based epoxy</td><td>Epoxy Technology</td><td>H20E</td><td></td></tr><tr><td>Sctoch tape</td><td>3M</td><td>801-1-18C</td><td></td></tr><tr><td>UHV valve</td><td>VAT</td><td>01034-KE01</td><td></td></tr><tr><td>linear/rotary feedthrough</td><td>Ferrovac</td><td>MD40</td><td></td></tr><tr><td>transfer rod</td><td>UHV design</td><td>PP series</td><td></td></tr><tr><td>wobble stick</td><td>Ferrovac</td><td>WM40</td><td></td></tr><tr><td>Paladin compact 355</td><td>Coherent</td><td></td><td></td></tr><tr><td>half waveplate</td><td>Kogakugiken</td><td></td><td>order made</td></tr><tr><td>Bipolar condenser bank</td><td>Tsuji electronics</td><td></td><td></td></tr></tbody></table>

experimental methods for spin- and angle-resolved photoemission spectroscopy combined with polarization-variable laser

このプロトコルの目的は、スピン角度分解光電子分光偏光可変 7 eV レーザー (レーザー SARPES)、結合を実行する方法を示し、固体物理学の勉強法の力を発揮することです。レーザー SARPES は、2 つの偉大な機能を実現します。まず、直線偏光レーザの軌道選択ルールを調べれば、軌道選択的励起可能様々 SAPRES 実験。第二に、技術は、光の偏光の関数としてスピン量子軸の変化の完全な情報を表示できます。レーザー SARPES でこれらの機能のコラボレーションの力を示すためには、Bi2Se3スピン軌道結合表面状態の調査のためこのテクニックを適用されます。この手法を affords スピン軌道結合波動関数からスピン ・軌道部品を分解します。また、偏波可変レーザーと共同で直接スピンの検出を使用する代表的な利点、テクニックは明確に 3 つの次元のスピン量子軸の偏光依存性を視覚化します。SARPES レーザー光電子分光法の機能が大幅に増加します。

SARPES 実験を開始、する前にkの位置で高エネルギー、角-解像度 (プロトコル 5.1 5.5) 高統計スピン統合角度分解光電子分光の結果を使用してスピン分解スペクトルを取るため正確に決定する必要があります。これは Bi2Se3単結晶の角度分解光電子分光の結果が表示されます図 7で示されます。この材料は、表面状態のスピン偏...

Watch this Scientific Journal Video about Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser at JoVE.com

Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

ここでは、固体状態におけるスピン軌道結合効果を視覚化するスピン角度分解光電子分光法による偏波可変 7 eV レーザーを組み合わせています。

偏波可変レーザーと組み合わせてスピン角度分解光電子分光の実験法

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser ...

experimental-methods-for-spin-angle-resolved-photoemission

Universidad San Sebastian

Research

JoVE Journal

Engineering

9.8K ビュー.  University of Tokyo. ここでは、固体状態におけるスピン軌道結合効果を視覚化するスピン角度分解光電子分光法による偏波可変 7 eV レーザーを組み合わせています。

ビデオ: Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures

The physical properties of a material are defined by its electronic structure. Electrons in solids are characterized by energy (&omega;) and momentum (k) and the probability to find them in a particular state with given &omega; and k is described by the spectral function A(k, &omega;). This function can be directly measured in an experiment based on the well-known photoelectric effect, for the explanation of which Albert Einstein received the Nobel Prize back in 1921. In the photoelectric effect the light shone on a surface ejects electrons from the material. According to Einstein, energy conservation allows one to determine the energy of an electron inside the sample, provided the energy of the light photon and kinetic energy of the outgoing photoelectron are known. Momentum conservation makes it also possible to estimate k relating it to the momentum of the photoelectron by measuring the angle at which the photoelectron left the surface. The modern version of this technique is called Angle-Resolved Photoemission Spectroscopy (ARPES) and exploits both conservation laws in order to determine the electronic structure, i.e. energy and momentum of electrons inside the solid. In order to resolve the details crucial for understanding the topical problems of condensed matter physics, three quantities need to be minimized: uncertainty* in photon energy, uncertainty in kinetic energy of photoelectrons and temperature of the sample.
In our approach we combine three recent achievements in the field of synchrotron radiation, surface science and cryogenics. We use synchrotron radiation with tunable photon energy contributing an uncertainty of the order of 1 meV, an electron energy analyzer which detects the kinetic energies with a precision of the order of 1 meV and a He3 cryostat which allows us to keep the temperature of the sample below 1 K. We discuss the exemplary results obtained on single crystals of Sr2RuO4 and some other materials. The electronic structure of this material can be determined with an unprecedented clarity.

The overall goal of this method is to determine the low-energy electronic structure of solids at ultra-low temperatures using Angle-Resolved Photoemission Spectroscopy with synchrotron radiation.

超低温での角度分解光電子分光

The physical properties of a material are defined by its  electronic structure. Electrons in solids are characterized by energy (&omega;)  and momentum ...

工学

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.

A protocol to detect and automate mode locking in a pre-adjusted nonlinear polarization rotation fiber laser is presented. The detection of a sudden change in the output polarization state when mode locking occurs is used to command the alignment of an intra-cavity polarization controller in order to find mode-locking conditions.

出力偏光測定を通じて非線形偏波回転ファイバレーザにおけるモードロックの自動化

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we demonstrate an optical spectroscopy method that is capable of resolving spectral features beyond that of the spin fine structure and homogeneous linewidth of single quantum dots (QDs) using a standard, easy-to-use spectrometer setup. This method incorporates both laser and photoluminescence spectroscopy, combining the advantage of laser line-width limited resolution with multi-channel photoluminescence detection. Such a scheme allows for considerable improvement of resolution over that of a common single-stage spectrometer. The method uses phonons to assist in the measurement of the photoluminescence of a single quantum dot after resonant excitation of its ground state transition. The phonon&#39;s energy difference allows one to separate and filter out the laser light exciting the quantum dot. An advantageous feature of this method is its straight forward integration into standard spectroscopy setups, which are accessible to most researchers.

The manuscript describes a method of phonon-assisted quasi-resonant fluorescence spectroscopy that incorporates both laser-limited resolution and photoluminescence (PL) spectroscopy. This method utilizes optical phonons to provide linewidth-limited resolution spectra of atom-like semiconductor structures in the energy domain. The method is also easily realized with a single spectrometer optical spectroscopy setup.

高解像度フォノンアシスト準共鳴蛍光分光

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we ...

Direct Imaging of Laser-driven Ultrafast Molecular Rotation

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb explosion imaging setup in which a hitherto-impractical camera angle is realized. In our imaging technique, diatomic molecules are irradiated with a circularly polarized strong laser pulse. The ejected atomic ions are accelerated perpendicularly to the laser propagation. The ions lying in the laser polarization plane are selected through the use of a mechanical slit and imaged with a high-throughput, 2-dimensional detector installed parallel to the polarization plane. Because a circularly polarized (isotropic) Coulomb exploding pulse is used, the observed angular distribution of the ejected ions directly corresponds to the squared rotational wave function at the time of the pulse irradiation. To create a real-time movie of molecular rotation, the present imaging technique is combined with a femtosecond pump-probe optical setup in which the pump pulses create unidirectionally rotating molecular ensembles. Due to the high image throughput of our detection system, the pump-probe experimental condition can be easily optimized by monitoring a real-time snapshot. As a result, the quality of the observed movie is sufficiently high for visualizing the detailed wave nature of motion. We also note that the present technique can be implemented in existing standard ion imaging setups, offering a new camera angle or viewpoint for the molecular systems without the need for extensive modification.

We present a protocol for creating a real-time movie of a molecular rotational wave packet using a high-resolution Coulomb explosion imaging setup.

レーザー駆動の超高速分子回転のダイレクトイメージング

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb ...

化学

Determination of the Excitation and Coupling Rates Between Light Emitters and Surface Plasmon Polaritons

We have developed a unique method to measure the excitation and coupling rates between the light emitters and surface plasmon polaritons (SPPs) arising from metallic periodic arrays without involving time-resolved techniques. We have formulated the rates by quantities that can be measured by simple optical measurements. The instrumentation based on angle- and polarization-resolved reflectivity and photoluminescence spectroscopy will be described in detail here. Our approach is intriguing due to its simplicity, which requires routine optics and several mechanical stages, and thus is highly affordable to most of the research laboratories.

This protocol describes the instrumentation for determining the excitation and coupling rates between light emitters and Bloch-like surface plasmon polaritons arising from periodic arrays.

励起と発光と表面プラズモンのレートを結合の定量

We have developed a unique method to measure the excitation and coupling rates between the light emitters and surface plasmon polaritons (SPPs) arising ...

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F&#8722;

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound electrons with neutral molecules/atoms. State-of-the-art in vacuo anion generation techniques allow application to a broad range of atomic, molecular, and cluster anion systems. These are separated and selected using time-of-flight mass spectrometry. Electrons are removed by linearly polarized photons (photo detachment) using table-top laser sources which provide ready access to excitation energies from the infra-red to the near ultraviolet. Detecting the photoelectrons with a velocity mapped imaging lens and position sensitive detector means that, in principle, every photoelectron reaches the detector and the detection efficiency is uniform for all kinetic energies. Photoelectron spectra extracted from the images via mathematical reconstruction using an inverse Abel transformation reveal details of the anion internal energy state distribution and the resultant neutral energy states. At low electron kinetic energy, typical resolution is sufficient to reveal energy level differences on the order of a few millielectron-volts, i.e., different vibrational levels for molecular species or spin-orbit splitting in atoms. Photoelectron angular distributions extracted from the inverse Abel transformation represent the signatures of the bound electron orbital, allowing more detailed probing of electronic structure. The spectra and angular distributions also encode details of the interactions between the outgoing electron and the residual neutral species subsequent to excitation. The technique is illustrated by the application to an atomic anion (F&#8722;), but it can also be applied to the measurement of molecular anion spectroscopy, the study of low lying anion resonances (as an alternative to scattering experiments) and femtosecond (fs) time resolved studies of the dynamic evolution of anions.

Here, we present a protocol for photoelectron imaging of anionic species. Anions generated in vacuo and separated by mass spectrometry are probed using velocity mapped photoelectron imaging, providing details of anion and neutral energy levels, anion and neutral structure and the nature of the anion electronic state.

F− 310 Nm 剥離によって示されている陰イオンの光電子イメージング

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound ...

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

We present a high-performance source of unconditional polarization-entangled photons that have a high-emission rate, a broadband distribution, are degenerated and postselection free. The property of the source is based on the multiple quantum interference effect with a round-trip configuration of a Sagnac interferometer. The quantum interference effects make it possible to use the high generation efficiency of the polarization-entangled photons to process parametric down-conversion, and separate degenerated photon pairs into different optical modes without a postselection requirement. The principle of the optical system was described and experimentally used to measure the fidelity and Bell parameters, and also to characterize the generated polarization-entangled photons from a minimum of six combinations of polarization correlated data. The experimentally obtained fidelity and Bell parameters exceeded the classical local correlation limit and are clear evidence of the generation of unconditional polarization-entangled photons.

We describe an optical system for the generation of unconditional polarization-entangled photons based on multiple quantum interference effects with a detection scheme to estimate the experimental fidelity of generated entangled photons.

複数の量子干渉に基づく無条件偏波絡み合った光子を生成するフォトニックシステム

We present a high-performance source of unconditional polarization-entangled photons that have a high-emission rate, a broadband distribution, are ...

Spectral and Angle-Resolved Magneto-Optical Characterization of Photonic Nanostructures

Photonic crystals are periodic nanostructures that can support a variety of confined electromagnetic modes. Such confined modes are usually accompanied by local enhancement of electric field intensity that strengthens light-matter interactions, enabling applications such as surface-enhanced Raman scattering (SERS) and surface plasmon enhanced sensing. In the presence of magneto-optically active materials, the local field enhancement gives rise to anomalous magneto-optical activity. Typically, the confined modes of a given photonic crystal depend strongly on the wavelength and incidence angle of the incident electromagnetic radiation. Thus, spectral and angular-resolved measurements are needed to fully identify them as well as to establish their relationship with the magneto-optical activity of the crystal. In this article, we describe how to use a Fourier-plane (back focal plane) microscope to characterize magneto-optically active samples. As a model system, here we use a plasmonic grating built out of magneto-optically active Au/Co/Au multilayer. In the experiments, we apply a magnetic field on the grating in situ and measure its reciprocal space response, obtaining the magneto-optical response of the grating over a range of wavelengths and incident angles. This information enables us to build a complete map of the plasmonic band structure of the grating and the angle and wavelength dependent magneto-optical activity. These two images allow us to pinpoint the effect that the plasmon resonances have on the magneto-optical response of the grating. The relatively small magnitude of magneto-optical effects requires a careful treatment of the acquired optical signals. To this end, an image processing protocol for obtaining magneto-optical response from the acquired raw data is laid out.

Photonic band structure enables understanding how confined electromagnetic modes propagate within a photonic crystal. In photonic crystals that incorporate magnetic elements, such confined and resonant optical modes are accompanied by enhanced and modified magneto-optical activity. We describe a measurement procedure to extract the magneto-optical band structure by Fourier space microscopy.

フォトニックナノ構造のスペクトルと角度分解磁気光学特性

Photonic crystals are periodic nanostructures that can support a variety of confined electromagnetic modes. Such confined modes are usually accompanied by ...

In Situ Measurement of Vacuum Window Birefringence using 25Mg+ Fluorescence

Accurate control of the polarization states of laser light is important in precision measurement experiments. In experiments involving the use of a vacuum environment, the stress-induced birefringence effect of the vacuum windows will affect the polarization states of laser light inside the vacuum system, and it is very difficult to measure and optimize the polarization states of the laser light in situ. The purpose of this protocol is to demonstrate how to optimize the polarization states of the laser light based on the fluorescence of ions in the vacuum system, and how to calculate the birefringence of vacuum windows based on azimuthal angles of external wave plates with Mueller matrix. The fluorescence of 25Mg+ ions induced by laser light that is resonant with the transition of |32P3/2,F = 4, mF&#160;= 4<img align="center" alt="Equation 100" src="/files/ftp_upload/61175/61175img1.jpg" style="color: rgb(68, 0, 68); font-size: 18px; font-weight: 700;" />&#160;&#8594;&#160;|32S1/2,F = 3, mF&#160;= 3<img align="center" alt="Equation 100" src="/files/ftp_upload/61175/61175img1.jpg" style="color: rgb(68, 0, 68); font-size: 18px; font-weight: 700;" />&#160;is sensitive to the polarization state of the laser light, and maximum fluorescence will be observed with pure circularly polarized light. A combination of half-wave plate (HWP) and quarter-wave plate (QWP) can achieve arbitrary phase retardation and is used for compensating the birefringence of the vacuum window. In this experiment, the polarization state of the laser light is optimized based on the fluorescence of 25Mg+ ion with a pair of HWP and QWP outside the vacuum chamber. By adjusting the azimuthal angles of the HWP and QWP to obtain maximum ion fluorescence, one can obtain a pure circularly polarized light inside the vacuum chamber. With the information on the azimuthal angles of the external HWP and QWP, the birefringence of the vacuum window can be determined.

In Situ Measurement of Vacuum Window Birefringence using 25Mg+ Fluorescence

Presented here is a method to measure the birefringence of vacuum windows by maximizing the fluorescence counts emitted by Doppler cooled 25Mg+ ions in an ion trap. The birefringence of vacuum windows will change the polarization states of the laser, which can be compensated by changing the azimuthal angles of external wave plates.

25Mg+蛍光を用いた真空窓複屈折のSitu測定

Accurate control of the polarization states of laser light is important in precision measurement experiments. In experiments involving the use of a vacuum ...

偏光感受性2光子顕微鏡による球晶石の特性評価

Polarization-Sensitive Two-Photon Microscopy for a Label-Free Amyloid Structural Characterization

Compared to its one-photon counterpart, two-photon excitation is beneficial for bioimaging experiments because of its lower phototoxicity, deeper tissue penetration, efficient operation in densely packed systems, and reduced angular photoselection of fluorophores. Thus, the introduction of polarization analysis in two-photon fluorescence microscopy (2PFM) provides a more precise determination of molecular organization in a sample compared to standard imaging methods based on linear optical processes. In this work, we focus on polarization-sensitive 2PFM (ps-2PFM) and its application in the determination of molecular ordering within complex bio-structures-amyloid spherulites. Neurodegenerative diseases such as Alzheimer's or Parkinson's are often diagnosed through the detection of amyloids-protein aggregates formed due to an impaired protein misfolding process. Exploring their structure leads to a better understanding of their creation pathway and consequently, to developing more sensitive diagnostic methods. This paper presents the ps-2PFM adapted for the determination of local fibril ordering inside the bovine insulin spherulites and spherical amyloidogenic protein aggregates. Moreover, we prove that the proposed technique can resolve the three-dimensional organization of fibrils inside the spherulite.

著者スポットライト:偏光感受性2光子顕微鏡を用いた複雑な生体構造の非侵襲的イメージング 

This paper describes how polarization-sensitive two-photon microscopy could be applied to characterize the local organization within label-free amyloid superstructures-spherulites. It also describes how to prepare and measure the sample, assemble the required setup, and analyze the data to obtain information about the local organization of amyloid fibrils.

偏光感受性2光子顕微鏡によるラベルフリーアミロイド構造解析

Compared to its one-photon counterpart, two-photon excitation is beneficial for bioimaging experiments because of its lower phototoxicity, deeper tissue ...

偏波可変レーザーと組み合わせてスピン角度分解光電子分光の実験法

要約

さらに動画を探す

この動画の章