Name: Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures (Video) | JoVE Journal
Uploaded: 2012-10-09T12:55:00.000+00:00
Duration: 8 min 53 s
Description: Learn high-resolution ARPES for mapping electronic structures in complex materials like Sr2RuO4 at ultra-low temperatures. This method reveals superconducting gaps and electron correlations with unprecedented clarity.

ai_agent_IP

ai_agent

maintenance

instantTrialDurationMinutes

isBiopharma

enableNewMyJoveSectionDesign

educationFeatures

seoMetaApi

ai_copilot_institution_blacklist

ai_chat_institution_blacklist

freeAccessWindow

ssoRoleCapture

scheduledMaintenanceBanner

joveLabsFeatures

disable_autoplay_for_bots

extended_trial_duration

5 minutes

We gratefully acknowledge the help of Rolf Follath, Roland H&uuml;bel, K. M&ouml;hler, Dmytro Inosov, J&ouml;rg Fink, Andreas Koitzsch, Bernd B&uuml;chner, Andrei Varykhalov, Emile Rienks, Oliver Rader, Setti Thirupathaiah, Denis Vyalikh, Sergey Molodtsov, Clemens Laubschat, Ramona Weber, Hermann D&uuml;rr, Wolfgang Eberhardt, Christian Jung, Thomas Blume, Gerd Reichardt, David Batchelor, Kai Godehusen, Martin Knupfer, Stefan Le&szlig;ny, Dirk Lindackers, Stefan Leger, Ralf Voigtl&auml;nder, Ronny Sch&ouml;nfelder, who conceived the "1-cubed" project, designed, constructed and commissioned the beamline and end-station as well as provided organizational and user support.
The project "1-cubed ARPES" has been funded by BMBF grant "Highest Resolution ARPES" as well as directly by BESSYII and IFW-Dresden. This particular work was supported by the DFG priority program SPP1458, grants ZA 654/1-1, BO1912/3-1 and BO1912/2-2. E.C. and B.P.D. thank the Faculty of Science at the University of Johannesburg for travel funding. A.V., R.F. and M.C. acknowledge support from the EU -FP7/2007-2013 under grant agreement N. 264098 - MAMA.

1.	Mounting the Sample
<ol>
 <li>This experiment uses synchrotron radiation produced by the BESSY storage ring of Helmholtz-Zentrum Berlin. The photons travel a beamline to our end-station where a sample is mounted.</li>
	<li>Begin with a single crystal of the material to be investigated, here strontium ruthenate. Use silver-based epoxy to glue the sample to the sample holder. The silver-based epoxy ensures good thermal and electrical contact.</li>
	<li>Glue an aluminum top-post to the surface of the single-crystal. The top-post will be used to cleave the sample in ultra-high vacuum to expose an atomically clean surface.</li>
	<li>Mount the sample holder in the load lock.</li>
</ol>
2.	Achieving Ultra-high Vacuum and Thermal Isolation
<ol>
 <li>Begin evacuating the load lock to minimize contamination of the ultra-high vacuum chamber.</li>
 <li>Monitor the pressure. Once a pressure of about 10-8 mbar has been achieved, transfer the assembly to the preparation chamber, and subsequently to the main chamber.The cold finger and sample holder have been specially designed to guarantee the best possible thermal contact with the helium pot.</li>
 <li>These demonstration versions show how this is achieved by using conical surfaces to increase the area of contact. The conical surfaces are pressed against one another and the sample holder and cold finger are firmly fixed in place using a titanium nut and bolt.</li>
</ol>
3.	Positioning and Cooling the Sample 
<ol>
 <li>The next step is to orient the sample within the cold finger along the azimuth using the transfer arm. Fix the position of the sample by tightening the nut while applying a counterforce with the supporting arm attached to the opposite side of the chamber.</li>
 <li>Cleave the sample by moving the manipulator upwards so that the top-post is removed by interaction with the supporting arm.</li>
 <li>With the beam shutter closed, move the sample into position in the beamline using the manipulator. Once the sample is in place, make sure the cryoshields are closed properly.</li>
 <li>Start pumping on the 1-K pot and circulate the helium-3 gas in order to cool the sample to the base temperature. The temperature is measured close to the sample and will not change during the experiment.</li>
 <li>Open the beam shutter of the beamline. Use the micrometer screws on the apparatus to adjust the position of the sample so that it is at the focus of the analyzer lens. This adjustment is crucial.</li>
</ol>
4.	Collecting Data
<ol>
 <li>Once the setup is ready, switch to the angle-resolved mode of the analyzer and record the spectrum in swept mode. This will generate data for two-dimensional energy-angle plots.</li>
 <li>Construct a Fermi surface map using the data. Select polar angles that correspond to Fermi level crossings for study of the superconducting gap of strontium ruthenate.</li>
 <li>Record high-resolution spectra at the chosen polar angles above and below the superconducting transition temperature of strontium ruthenate to investigate the behavior of the superconducting gap.</li>
</ol>

<ol><li>Borisenko, S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((One-Sign+Order+Parameter+in+Iron+Based+Superconductor%5BTitle%5D)+AND+%22Symmetry%22%5BJournal%5D)">One-Sign Order Parameter in Iron Based Superconductor.</a> Symmetry. 4, 251-264 (2012).</li>
<li>Maeno, Y., Hashimoto, H., Yoshida, K., Nishizaki, S., Fujita, T., Bednorz, J. G., Lichtenberg, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Superconductivity+in+a+layered+perovskite+without+copper%5BTitle%5D)+AND+%22Nature+%28London%29%22%5BJournal%5D)">Superconductivity in a layered perovskite without copper.</a> Nature (London). 372, 532(1994).</li>
<li>Singh, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Relationship+of+Sr2RuO4+to+the+superconducting+layered+cuprates%5BTitle%5D)+AND+%22Phys.+Rev.+B%22%5BJournal%5D)">Relationship of Sr2RuO4 to the superconducting layered cuprates.</a> Phys. Rev. B. 52, 1358(1995).</li>
<li>Zabolotnyy, V. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Surface+and+bulk+electronic+structure+of+the+unconventional+superconductor+Sr2RuO4%3A+unusual+splitting+of+the+%CE%B2+band%5BTitle%5D)+AND+%22New+Journal+of+Physics%22%5BJournal%5D)">Surface and bulk electronic structure of the unconventional superconductor Sr2RuO4: unusual splitting of the β band.</a> New Journal of Physics. 14, 63039(2012).</li>
<li>Stöwe, K., Wagner, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Crystal+Structure+and+Calculated+Electronic+Band+Structure+of+ZrTe3%5BTitle%5D)+AND+%22Journal+of+Solid+State+Chemistry%22%5BJournal%5D)">Crystal Structure and Calculated Electronic Band Structure of ZrTe3.</a> Journal of Solid State Chemistry. 138, 160-168 (1998).</li>
<li>Zabolotnyy, V. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Momentum+and+temperature+dependence+of+renormalization+effects+in+the+high-temperature+superconductor+YBa2Cu3O7-%CE%B4%5BTitle%5D)+AND+%22Phys.+Rev.+B%22%5BJournal%5D)">Momentum and temperature dependence of renormalization effects in the high-temperature superconductor YBa2Cu3O7-δ.</a> Phys. Rev. B. 76, 064519(2007).</li>
<li>Zabolotnyy, V. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Disentangling+surface+and+bulk+photoemission+using+circularly+polarized+light%5BTitle%5D)+AND+%22Phys.+Rev.+B%22%5BJournal%5D)">Disentangling surface and bulk photoemission using circularly polarized light.</a> Phys. Rev. B. 76, 024502(2007).</li>
<li>Kordyuk, A. A., Borisenko, S. V., Kim, T. K., Nenkov, K. A., Knupfer, M., Fink, J., Golden, M. S., Berger, H., Follath, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Origin+of+the+Peak-Dip-Hump+Line+Shape+in+the+Superconducting-State+%28%CF%80%2C0%29+Photoemission+Spectra+of+Bi2Sr2CaCu2O8%5BTitle%5D)+AND+%22Phys.+Rev.+Lett%22%5BJournal%5D)">Origin of the Peak-Dip-Hump Line Shape in the Superconducting-State (π,0) Photoemission Spectra of Bi2Sr2CaCu2O8.</a> Phys. Rev. Lett. 89, 077003(2002).</li>
<li>Inosov, D. S., Fink, J., Kordyuk, A. A., Borisenko, S. V., Zabolotnyy, V. B., Schuster, R., Knupfer, M., B?chner, B., Follath, R., D?rr, H. A., Eberhardt, W., Hinkov, V., Keimer, B., Berger, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Momentum+and+Energy+Dependence+of+the+Anomalous+High-Energy+Dispersion+in+the+Electronic+Structure+of+High+Temperature+Superconductors%5BTitle%5D)+AND+%22Phys.+Rev.+Lett%22%5BJournal%5D)">Momentum and Energy Dependence of the Anomalous High-Energy Dispersion in the Electronic Structure of High Temperature Superconductors.</a> Phys. Rev. Lett. 99, 237002(2007).</li>
<li>Inosov, D. S., Schuster, R., Kordyuk, A. A., Fink, J., Borisenko, S. V., Zabolotnyy, V. B., Evtushinsky, D. V., Knupfer, M., B?chner, B., Follath, R., Berger, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Excitation+energy+map+of+high-energy+dispersion+anomalies+in+cuprates%5BTitle%5D)+AND+%22Phys.+Rev.+B%22%5BJournal%5D)">Excitation energy map of high-energy dispersion anomalies in cuprates.</a> Phys. Rev. B. 77, 212504(2008).</li>
<li>Hüfner, S. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aH%C3%BCfner%2C+S+%22Photoelectron+Spectroscopy%2C+Principles+and+Applications%22">Photoelectron Spectroscopy, Principles and Applications</a>. , 2nd Edition, Springer Verlag. Heidelberg. (1996).</li>
</ol>

No conflicts of interest declared.

As is shown above, the implemented method is very efficient in studying the low-energy electronic structure of single crystals. Recent instrumental improvements have turned ARPES from a mere characterization and band-mapping tool into a sophisticated many-body spectroscopy. A modern experiment delivers information about the electronic structure of a solid or a nano-object with a new level of precision. Access to the Fermi surface in the case of a metal, energy gaps of semiconductors and insulators, their surface st...

Nowadays ARPES is widely used to determine the electronic structure of solids. Usually, different variations of this method are defined by the source of the radiation needed to excite the electrons. We use synchrotron radiation since it offers a unique opportunity to tune the polarization and the excitation photon energy in a wide energy range and is characterized by high intensity, small bandwidth (uncertainty in energy hn) and it can be focused to a narrow beam to collect photoelectrons from a spot of a few tens of microns. Synchrotron radiation is generated in electron storage rings forcing electrons circulating in the ring with an energy of the order of 2 GeV ** to pass through periodic arrangements of strong magnets (undulators). The magnetic field deflects the electrons and when such fast electrons change their direction they emit radiation. Exactly this radiation is then directed into the so called beamline where it is further monochromatized by a diffraction grating and focused on the surface of the sample by several mirrors. There are many such facilities around the world. Our end-station is located at one of the beamlines of the BESSY storage ring which belongs to the Helmholtz-Zentrum Berlin.
The heart of this ARPES facility is the electron-energy analyzer (Figure 1). Since we are interested in both the kinetic energy and angle at which electrons leave the surface, it is very convenient to detect them in one measurement. A very simple principle makes this approach a reality. As in a basic experiment with an optical lens, which focuses a plane wave into the point in the back focal plane thus performing spatial Fourier transformation, the electron optical lens projects electrons which left the surface at particular angle to a point in the focal plane (Figure 1). In such a way we gain access to the reciprocal, i.e. momentum, space. The distance from the forward direction in the focal plane corresponds to the angle and thus to the momentum of the photoelectron. Now the electrons have to be analyzed in terms of energy. For this purpose the entrance slit of the hemispherical analyzer is placed exactly in the focal plane of the electron optical lens. Voltages on two hemispheres are chosen such that only electrons with particular kinetic energy (pass energy) will be guided exactly in the middle of two hemispheres and land on the central line of the two dimensional detector. Those which are faster will hit the detector closer to the outer hemisphere; those which are slower will be deflected towards the inner hemisphere. In such a way we can get the photoemission intensity distribution as a function of angle and kinetic energy simultaneously.
The main advantage of our approach over existing methods is the use of the He3 cryomanipulator. There are at least two reasons to carry out the measurements at low temperatures. The higher the temperature of the material, the more smeared out the electronic states become in energy and momentum. To determine the electronic structure with high precision this temperature broadening has to be avoided. Also, many physical properties are temperature dependent, some ordering phenomena set in at low temperatures and the knowledge of the electronic structure in the ground state of the system, i.e. at T=0, is of fundamental importance. One of the most effective ways to cool down the sample down to tenths of a Kelvin is to liquefy He3 gas. In many experiments reaching sub-Kelvin temperatures is not a problem, since thermal radiation, the main enemy of ultra-low temperatures, can be effectively shielded. Unfortunately, this is not the case in photoemission experiments. We need to provide free access for the incoming light and outgoing electrons. This is realized by specially designed slits in three radiation shields, having different temperatures. In order to compensate for the heat load caused by the photon beam and room-temperature radiation, the cooling power of the cryostat should be very high. This is achieved by the very large pumping speed of two pumps which reduce the vapor pressure above the liquid He3, thus cooling the cold finger and sample. The design specifications of our He3 system make it the most powerful worldwide. It is perhaps the only place on the planet where one can see a 1 K cold surface through a room temperature window, the "coldest visible".
The sketch of the modern photoemission experiment is shown in Figure 1. The synchrotron beam (dashed green line) illuminates the 1 K cold surface of the sample and excites photoelectrons. Electrons are projected to the entrance slit of the hemispherical analyzer, sorted in terms of angle (yellow, magenta and cyan traces correspond to different tilt angles) and then are analyzed in terms of kinetic energy. Figure 2 shows the typical intensity distribution as a function of tilt angle and kinetic energy. Such an intensity distribution is indeed expected as the comparison with band structure calculations of this material shows (right panel). This is our window into reciprocal space.
By scanning voltages on the lens and hemispheres and rotating the sample around the vertical axis (polar angle) we can explore the broad binding energy range as well as wide regions of the reciprocal space with unprecedented detail. In particular, plotting intensity at the Fermi level as a function of both components of the in-plane momentum, calculated from tilt and polar angles, we have direct access to the Fermi surface (FS).
* Under "uncertainty" we understand the experimenter's best estimate of how far an experimental quantity might be from the "true value."
** The low-energy ring can have an energy of ~0.8 GeV, the high-energy one - up to 8 GeV.

<table><tbody><tr><td>Single crystals of ZrTe&lt;sub&gt;3&lt;/sub&gt; and TiSe&lt;sub&gt;2&lt;/sub&gt;</td><td></td><td></td><td>grown by Dr Helmut Berger, EPFL, Lausanne</td></tr><tr><td>Single crystals of Sr&lt;sub&gt;2&lt;/sub&gt;RuO&lt;sub&gt;4&lt;/sub&gt;</td><td></td><td></td><td>grown by the group of Dr Antonio Vecchione</td></tr><tr><td colspan="4">&lt;strong&gt;SAMPLES&lt;/strong&gt;&lt;br/&gt; ZrTe&lt;sub&gt;3&lt;/sub&gt;, TiSe&lt;sub&gt;2&lt;/sub&gt;, Sr&lt;sub&gt;2&lt;/sub&gt;RuO&lt;sub&gt;4&lt;/sub&gt;</td></tr></tbody></table>

angle-resolved photoemission spectroscopy at ultra-low temperatures

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 ultra-low temperatures of our setup together with the high resolution of the beamline and analyzer allow us to record spectra with very high overall resolution. This is illustrated in Figure 3. The usual test of the energy resolution is to measure the width of the Fermi edge of a metal. In this case it is a freshly evaporated indium film. The full width at half maximum (FWHM) of the Gaussian, which when convoluted with the step-function precisely describes the edge, is of the order of 2 meV. Of more ...

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.

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

The overall goal of the following experiment is to determine the low energy electronic structure of solids at ultra-low temperatures using angle resolved photo emission spectroscopy or arrp pez with synchrotron radiation. In the synchrotron radiation facilities, ultra high vacuum chamber attached to the beam line, a single crystal of the studied material is cleaved, exposing an atomically clean surface as a second step. The sample is cooled below one Kelvin, which ensures minimal temperature broadening and proximity to the ground state of the material.Next, the photo emission intensity is recorded as a function of tilt, angle and energy and static geometry. By rotating the sample information can be collected from a large portion of momentum energy space needed to obtain the firming surface map and dispersions close to the firm level Results are obtained that show that low energy electronic structure of complex materials can be determined with unprecedented clarity and resolution. Using the helium three cryo manipulator and synchrotron based arrp e Angle result for the emission spectroscopy is a technique based on a simple photoelectric effect, which has been discovered and explained more than a century ago.We use this technique today in order to determine the electronic structure of solids with a very high precision. In our approach. We use three latest achievements in the fields of synchrotron radiation, surface science, and cryogenics.We use tuneable exudation photo images, which contributed in certainty of one milli electron Walt. We detect the kinetic energy of our photo electrons with uncertainty of one milli electron Walt, and what is more important? We use helium three cryostat, which allows to keep the temperature of our samples below one column.Because of these three ones we call our system one cube, We use a specially designed helium three cryostat, which provides a free access for the incoming light and outgoing electrons. The design of our system makes it the most powerful in the world.Actually. With this system, it is possible to see a surface at one column through the room temperature window.With this technique and this setup, we can answer key questions in the field of electronic systems. In particular for superconductivity, we can determine the structure of the other parameter to find out what drives the phenomenon. This experiment uses the synchrotron radiation produced by the Bessie storage ring of the helm, Holt Centrum Berlin.The photons travel a beamline to our end station where a sample is mounted. Begin with a single crystal of the material to be investigated here. STR urinate use silver based epoxy to glue the sample to the sample holder.The silver based epoxy ensures good thermal and electrical contact glue. An aluminum top post to the surface of the single crystal. The top post will be used to cleave the sample in ultra high vacuum to expose an anatomically clean surface mount, the sample holder in the load lock begin evacuating the load lock to minimize contamination of the ultra high vacuum chamber.Monitor the pressure. Once a pressure of about 10 to the minus eight millibar has been achieved, transfer the assembly to the preparation chamber and subsequently to the main chamber. The cold finger and sample holder have been specially designed to guarantee the best possible thermal contact with the helium pot.These demonstration versions show how this is achieved by using conical surfaces to increase the area of contact. The conical surfaces are pressed against one another, and the sample holder and cold finger are firmly fixed in place using a titanium nut and bolt. The transfer system has been designed to minimize thermal contact with the assembly as seen in this demonstration unit.This is accomplished by using a thin titanium tube with multiple openings as the main carrying element of the assembly. At the end of the transfer arm, a spring activated screwdriver inside the assembly is used to adjust the angular position of the sample. The next step is to orient the sample within the cold finger along the asmuth using the transfer arm.Fix the position of the sample by tightening the nut while applying a counterforce with the supporting arm attached to the opposite side of the chamber. Clea the sample by moving the manipulator upward so that the top post is removed by interaction with the supporting arm. With the beam shutter closed, move the sample into position in the beam line using the manipulator.Once the sample is in place, make sure the cryo shields are closed properly. Start pumping on the one kelvin pot and circulate the helium three gas in order to cool the sample to the base temperature. Open the beam shutter of the beam line.Use the micrometer screws on the apparatus to adjust the position of the sample so that it is at the focus of the analyzer lens. This adjustment is crucial. Once the setup is ready, switch to the angle resolved mode of the analyzer and record the spectrum in swept mode.This will generate data for two dimensional energy angle plots. Conduct a fury surface map using the data. Select polar angles that correspond to firmly level crossings.For study of the superconducting gap of stratum urinate record high resolution spectra at the chosen polar angles above and below the superconducting transition temperature of the stratum urinate to investigate the behavior of the superconducting gap. Shown here is the photo electron intensity as a function of tilt angle and energy. For a sample of zirconium three Telluride.Compare this with the theoretical band structure calculation for the same material. A standard test for energy resolution is to measure the full width at half maximum of the Gaussian, which when convoluted with the step function describes the firm edge. The Gaussian full width at half maximum used fit.This data for freshly evaporated indium is of order, two milli electron vols. Here is a plot of the energy distribution curve in a superconducting sample of lithium ion arsenide taken with the system. As another example of the resolution that can be achieved here is the momentum distribution curve at the firming level of zirconium three Telluride.The anticipated overall energy resolution of the system is expressed by the formula shown here. The actual performance is very close to this goal. On the left is a typical spectrum taken to study the superconducting gap of stratum brunate for T equals 970 millikelvin.The arrow indicates momentum corresponding to the energy distribution curve on the right. The image on the right shows the shift of the leading edge of the integrated energy distribution curve for a sample of str and urinate above and below the superconducting transition temperature. The spectrum used for the calculation is shown on the left.The momentum window is indicated by the width of the red arrow. The gap corresponds to a firming surface point on the band near the Brill wall zone diagonal as another example. Here is the shift of the energy distribution curve as a function of temperature from another point on the firmi surface of strate.Finally, the system allows measurement of the typical temperature behavior of the binding energy of the leading edge in the vicinity of the crossing of two fury surfaces. Once mastered, this technique can be done within eight hours if everything is performed properly. That is within one shift of a typical syn zone operation.While attempting this procedure, it is very important to follow all the describable steps with high degree of precautions, luing the sample during the sample transfer. Unsuccessful cleavage because of bad sample preparation or just poor adjustments, all could lead to failure of the whole experiment. This technique provides the information about the electronic structure of a solid or inana objects.With the new level of precision, we have access to the firm surface maps, bend dispersion and comparison with this data, with the EB bend structure calculations allows us to determine the bandwidth randomization or velocity normalization. Thus, we can judge about the complexity of the materials in terms of the correlations. Defined structures near the firm level allow to detect the fingerprints of the interaction between the electrons and other degrees of freedom like phonons, plasmin, or magnets.Using the systematic momentum dependent study, one can see the dependence of the superconducting gap as a function of momentum. Thus getting the information about the all the parameter, its symmetry and structure. This experiment can provide the ultimate test for the existing theories as well as stimulate new paths of inquiry.

angle-resolved-photoemission-spectroscopy-at-ultra-low-temperatures

Research

JoVE Journal

Engineering

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.

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

Europium thenoyltrifluoroacetonate (EuTFC) has an optical luminescence line at 612 nm, whose activation efficiency decreases strongly with temperature. If a sample coated with a thin film of this material is micro-imaged, the 612 nm luminescent response intensity may be converted into a direct map of sample surface temperature.

High-resolution Thermal Micro-imaging Using Europium Chelate Luminescent Coatings

A simple liquid nitrogen Dewar/cryostat apparatus comprised of a small fused silica optical Dewar, a thermocouple, and a charge-coupled device (CCD) spectrograph are described. The experiments for which this Dewar/cryostat is designed require fast sample loading, freezing, and alignment, accurate and stable sample temperatures, and small size/portability.

A Simple Dewar/Cryostat for Thermally Equilibrating Samples at Known Temperatures for Accurate Cryogenic Luminescence Measurements

Here, we present a method of the spectroscopic characterization of organic molecules by means of time-resolved photoluminescence spectroscopy on the nanosecond-to-millisecond timescale in oxygen-free conditions. Methods to efficiently remove oxygen from the samples and, thus, limit luminescence quenching are also described.

Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera

We demonstrate an all-electronic method to observe nanosecond-resolved charge dynamics of dopant atoms in silicon with a scanning tunneling microscope.

All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics

This protocol describes the key steps for performing and analyzing pump-probe experiments combining a femtosecond optical laser with a free-electron laser in order to study ultrafast photochemical reactions in gas-phase molecules.

An Experimental Protocol for Femtosecond NIR/UV - XUV Pump-Probe Experiments with Free-Electron Lasers

Here, we combine polarization-variable 7-eV laser with spin- and angle-resolved photoemission technique to visualize the spin-orbital coupling effect in solid states.

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

Here, we present a protocol for typical experiments of soft X-ray absorption spectroscopy (sXAS) and resonant inelastic X-ray scattering (RIXS) with applications in battery material studies.

Elemental-sensitive Detection of the Chemistry in Batteries through Soft X-ray Absorption Spectroscopy and Resonant Inelastic X-ray Scattering

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.

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

We present a protocol for probing ultrafast vibrational coherences in polyatomic radical cations that result in molecular dissociation.

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization

Learn high-resolution ARPES for mapping electronic structures in complex materials like Sr2RuO4 at ultra-low temperatures. This method reveals superconducting gaps and electron correlations with unprecedented clarity.

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures

Explore More Videos