The 7 th Day After First Light
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The 7 th Day After First Light Yu He SC Meeting Jul 25, 2013 • Milestones • Early Guinea Pigs • PROBLEMS! Metal Cuprate Topological Insulator Pnictide FeSe Film
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The 7 th Day After First Light. Yu He SC Meeting Jul 25, 2013. Milestones. Early Guinea Pigs. Metal Cuprate Topological Insulator Pnictide FeSe Film. PROBLEMS!. The Laser. Ionization Chamber (IC-P). Gas Conversion Module (GCM). ARPES Manifold. Dispersion Chamber (DC). - PowerPoint PPT Presentation
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The 7th Day After First LightYu HeSC MeetingJul 25, 2013MilestonesEarly Guinea PigsPROBLEMS!MetalCuprateTopological InsulatorPnictideFeSe FilmThe Laser
Seed laser, 100MHz, IRAmplifier, SHG and FHGGas Conversion Module (GCM)Dispersion Chamber (DC)Ionization Chamber (IC-P)ARPES ManifoldGas Control Panel (GCP)Milestones
Jul 10Jul 11
Jul 07Jul 12Jul 15Jul 20
Jul 16
The Gold Standard
By proper beam alignment, two step puzzle solvedBest Au resolution ~10meVUD92 Bi2212 half wave plate rotation
Polarization changes intensity by 2 foldsSignal-background ratio modulatedTo be motorizedTo add quarter-wave plateUD92 Bi2212 reaching zone boundary
Reaching zone boundary!Need better stats and even longer time per scanBi2Se3 characterize polarization?
Bi2Se3 linear dichroism
Z.-H. Zhu et al, PRL 110, 216401 (2013)P-polarization dominatesWhat exactly is the half-wave plate doing to the linear polarization of 11eV?0.2eV0.1eV0 eV-0.1eVBi2Se3 Bi2Se3 circular dichroism
Z.-H. Zhu et al, PRL 110, 216401 (2013)
0.2eV
0.1eVBi2Se3 Bi2Se3 circular dichroism
Z.-H. Zhu et al, PRL 110, 216401 (2013)
0.2eVSmall circular dichroism existsLinear dichroism dominatesRotating half wave plate by doesnt simply rotate linear polarization by 2
0.1eVFeTeSe blur band and space charging
UV power411uW334uW223uW140uW
Strong evidence for space charging
Down to 150k counts/second at EF the effect is still visible
Whats wrong?FeTeSe blur band and space chargingPulse durationAverage powerRepetion rate11eV~1ns~5uW1MHz6eV~10ps~?uW80MHzSPEAR31-100ps10uW @500mA500MHz-1MHz
12FeSe film reaching zone boundary
M18Khv = 21.218eVHelium plasma dischargehv = 10.897eV1024nm+256nm+256nmFeSe film reaching zone boundary
Back bending clearly observed below Tc
Less background at low binding energy
Fully reaching zone boundary powerful tool to study fine structures and subtle changes at M pointProblems!
Space Charging
Polarization
ResolutionIncrease rep rate to 10MHz or moreThe limiting factor: power or spot size?Pass energy to get around?How keen are we now perusing 100uW power?MotorizeWhat does the wave plate exactly do upstream the GCM?Quarter wave plate for circular dichroismGo beyond 10meV how about 1meV?The END
