Name: visualizing uniaxial-strain manipulation of antiferromagnetic domains in fe1+yte using a spin-polarized scanning tunneling microscope
Uploaded: 2019-03-24T14:00:00
Description: Watch this Scientific Journal Video about Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope at JoVE.com

P.A. acknowledges support from the U.S. National Science Foundation (NSF) CAREER under award No. DMR-1654482. Material synthesis was carried out with the support of the Polish National Science Centre grant No 2011/01/B/ST3/00425.

NOTE: The U-shaped body is made of 416-grade stainless steel, which is stiff and has a low coefficient of thermal expansion (CTE), ~9.9 &#956;m/(m&#8729;&#176;C), as compared to ~17.3 &#956;m/(m&#8729;&#176;C) for 304-grade stainless steel.
1. Mechanical uniaxial-strain device
<ol>
	<li>Clean the U-shaped device, the micrometer screws (1&#8211;72 corresponding to 72 rotations per inch), the Belleville spring disks, and the base plate by sonicating them separately in acetone first and then in...

<ol>
	<li>Paglione, J., Greene, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-temperature+superconductivity+in+iron-based+materials.">High-temperature superconductivity in iron-based materials.</a> Nature Physics. 6 (9), 645 (2010).</li><li>Keimer, B., Kivelson, S. A., Norman, M. R., Uchida, S., Zaanen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+quantum+matter+to+high-temperature+superconductivity+in+copper+oxides.">From quantum matter to high-temperature superconductivity in copper oxides.</a> Nature. 518, 179-186 (2015).</li><li>Anderson, P. 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D., Haghighirad, A. A., Rhodes, L. C., Hoesch, M., Kim, T. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gigantic+anisotropic+uniaxial+pressure+effect+on+superconductivity+within+the+CuO2+plane+of+La1.64Eu0.2Sr0.16CuO4:+Strain+control+of+stripe+criticality.">Gigantic anisotropic uniaxial pressure effect on superconductivity within the CuO2 plane of La1.64Eu0.2Sr0.16CuO4: Strain control of stripe criticality.</a> Journal of the Physical Society of Japan. 73 (5), 1123-1126 (2004).</li><li>Kuo, H. -. H., Shapiro, M. C., Riggs, S. C., Fisher, I. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+the+elastoresistivity+coefficients+of+the+underdoped+iron+arsenide+Ba(Fe0.975Co0.025)2As2.">Measurement of the elastoresistivity coefficients of the underdoped iron arsenide Ba(Fe0.975Co0.025)2As2.</a> Physical Review B. 88 (8), 085113 (2013).</li><li>He, 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=Dichotomy+between+in-plane+magnetic+susceptibility+and+resistivity+anisotropies+in+extremely+strained+BaFe2As2.">Dichotomy between in-plane magnetic susceptibility and resistivity anisotropies in extremely strained BaFe2As2.</a> Nature Communications. 8 (1), 504 (2017).</li><li>Engelmann, J., 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=Strain+induced+superconductivity+in+the+parent+compound+BaFe2As2.">Strain induced superconductivity in the parent compound BaFe2As2.</a> Nature Communications. 4 (2877), 2877 (2013).</li><li>Berger, A. 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N., 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> Temperature Driven Topological Switch in 1T’-MoTe2 and Strain Induced Nematicity in NaFeAs. , (2018).</li><li>B&#246;hmer, A., 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=Effect+of+biaxial+strain+on+the+phase+transitions+of+Ca(Fe1&#8722;xCox)2As2.">Effect of biaxial strain on the phase transitions of Ca(Fe1&#8722;xCox)2As2.</a> Physical Review Letters. 118 (10), 107002 (2017).</li><li>Bao, W., 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=Tunable+(&#948;+&#960;,+&#948;+&#960;)-type+antiferromagnetic+order+in+&#945;-Fe(Te,Se)+superconductors.">Tunable (&#948; &#960;, &#948; &#960;)-type antiferromagnetic order in &#945;-Fe(Te,Se) superconductors.</a> Physical Review Letters. 102 (24), 247001 (2009).</li><li>Koz, C., R&#246;&#223;ler, S., Tsirlin, A. 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All operations required to move the samples into and inside the STM are carried out using sets of arm manipulators. The STM is maintained at low temperatures by liquid nitrogen and liquid helium, and the sample cools down for at least 12 h before being approached. This allows the sample and microscope temperature to reach thermal equilibrium. To isolate electric and acoustic noise, the STM is placed in an acoustic and radio frequency shielded room. The microscope head is further suspended from springs for optimized instr...

High-temperature superconductivity in cuprates and iron-based superconductors is an intriguing state of quantum matter1,2. A major challenge in understanding superconductivity is the locally intertwined nature of various broken symmetry states, such as electronic nematic and smectic phases (that break rotational and translational symmetries of the electronic states), with superconductivity3,4,5,6,7. Manipulation and deliberate tuning of these broken symmetry states is a key objective toward understanding and controlling superconductivity.
Controlled strain, both uniaxial and biaxial, is a well-established technique to tune the collective electronic states in condensed matter systems8,9,10,11,12,13,14,15,16,17,18,19,20,21,22. This clean tuning, without the introduction of disorder through chemical doping, is commonly used in various kinds of experiments to tune bulk electronic properties23,24,25,26. For example, uniaxial pressure has proved to have an immense effect on superconductivity in Sr2RuO413 and cuprates27 and on the structural, magnetic, and nematic phase transitions of iron-based superconductors10,14,28,29 and was recently demonstrated in tuning the topological states of SmB624. However, the use of strain in surface-sensitive techniques, such as STM and angle-resolved photoemission spectroscopy (ARPES), has been limited to in situ-grown thin films on mismatched substrates26,30. The major challenge with applying strain to single crystals in surface-sensitive experiments is the need to cleave the strained samples in ultrahigh vacuum (UHV). In the last few years, an alternative direction has been to epoxy a thin sample on piezo stacks9,10,18,31 or on plates with different coefficients of thermal expansion19,32. Yet in both cases, the magnitude of the applied strain is quite limited.
Here we demonstrate the use of a novel mechanical uniaxial-strain device that allows researchers to strain a sample (compressive strain) without constraints and simultaneously visualize its surface structure using STM (see Figure 1). As an example, we use single crystals of Fe1+yTe, where y = 0.10, the parent compound of the iron chalcogenide superconductors (y is the excess iron concentration). Below TN = ~60 K, Fe1+yTe transitions from a high-temperature paramagnetic state into a low-temperature antiferromagnetic state with a bicollinear stripe magnetic order26,33,34&#160;(see Figure 3A,B). The magnetic transition is further accompanied by a structural transition from tetragonal to monoclinic26,35. The in-plane AFM order forms detwinned domains with the spin structure pointing along the long b-direction of the orthorhombic structure34. By visualizing the AFM order with spin-polarized STM, we probe the bidirectional domain structure in unstrained Fe1+yTe samples and observe their transition into a single large domain under applied strain (see the schematic in Figure 3C-E). These experiments show the successful surface tuning of the single crystals using the uniaxial-strain device presented here, the cleaving of the sample, and the simultaneous imaging of its surface structure with the scanning tunneling microscope. Figure 1 shows the schematic drawings and pictures of the mechanical strain device.

<table border="0" cellpadding="0" cellspacing="0" style="width:668px;" width="668">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Belleville spring disks</td>
			<td style="width:167px;">McMaster Carr</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Fe(1.1)Te</td>
			<td style="width:167px;"></td>
			<td style="width:119px;"></td>
			<td>Single Crystal</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">H20E</td>
			<td style="width:167px;">Epoxy Technology</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">H74F</td>
			<td style="width:167px;">Epoxy Technology</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Micrometer screws</td>
			<td style="width:167px;">McMaster Carr</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Stainless Steel sheets (416)</td>
			<td style="width:167px;">McMaster Carr</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

visualizing uniaxial-strain manipulation of antiferromagnetic domains in fe1+yte using a spin-polarized scanning tunneling microscope

The quest to understand correlated electronic systems has pushed the frontiers of experimental measurements toward the development of new experimental techniques and methodologies. Here we use a novel home-built uniaxial-strain device integrated into our variable temperature scanning tunneling microscope that enables us to controllably manipulate in-plane uniaxial strain in samples and probe their electronic response at the atomic scale. Using scanning tunneling microscopy (STM) with spin-polarization techniques, we visualize antiferromagnetic (AFM) domains and their atomic structure in Fe1+yTe samples, the parent compound of iron-based superconductors, and demonstrate how these domains respond to applied uniaxial strain. We observe the bidirectional AFM domains in the unstrained sample, with an average domain size of ~50-150 nm, to transition into a single unidirectional domain under applied uniaxial strain. The findings presented here open a new direction to utilize a valuable tuning parameter in STM, as well as other spectroscopic techniques, both for tuning the electronic properties as for inducing symmetry breaking in quantum material systems.

STM topographs were measured in constant current mode with a setpoint bias of -12 meV applied to the sample and a setpoint current of -1.5 nA collected on the tip. Pt-Ir tips were used in all experiments. To achieve spin-polarized STM, the scanning tunneling microscope tip has to be coated with magnetic atoms, which can be quite challenging. In this case of studying Fe1+yTe, the sample itself provides a simple means of achieving this. The excess irons (y...

Watch this Scientific Journal Video about Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope at JoVE.com

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope

Using uniaxial strain combined with spin-polarized scanning tunneling microscopy, we visualize and manipulate the antiferromagnetic domain structure of Fe1+yTe, the parent compound of iron-based superconductors.

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope

The quest to understand correlated electronic systems has pushed the frontiers of experimental measurements toward the development of new experimental ...

This protocol is significant because it is a visualization of the integration of the uniaxial-strain device with scanning tunneling microscopy. It involves both applying strain and visualizing the manipulation of structural domains in SDM. The main advantage of this technique is it allows for increased amounts of strain since it's a mechanical device.It's surface effects are able to be visualized using scanning tunneling microscopy. In high temperature superconductors by deliberately tuning and manipulating broken symmetry states, one can control and understand superconductivity. This process can be applied to any material provided it's a single crystal and it is SDM-compatible.There's a lot of device testing to determine the set-up's response to varying conditions including how much strain can be achieved. It's a very challenging experiment where patience and absolute understanding of what you are doing is key. Visual demonstration of this process is critical, as it gives an insight into making and using the described device with SDM which is a complex process.To begin, disassemble the u-shaped device and place it into acetone. Clean the device, the micrometer screws, the Belleville spring discs, and the base plate by sonicating them for 20 minutes. Then, transfer them into isopropanol and sonicate them for an additional 20 minutes.Once clean, bake the device components in an oven for 15 to 20 minutes to get rid of any water residue and to degas. Then, using a sharp razor blade, cut the iron tellurium sample to one millimeter by two millimeters by 0.1 millimeters in size. Finally, assemble the parts together.The opening inside the u is one millimeter and can be tuned smaller or large by a pair of micrometer screws located on the sides of the device. In two separate dishes, mix silver epoxy and non-conductive epoxy according to the instructions on the epoxy data sheets. Then, apply a thin layer of silver epoxy to create an electrical contact and mount the sample across the one millimeter gap so that its long axis is oriented along the b axis of the iron tellurium sample.Place the sample holder and sample into a convection oven and bake them for 15 minutes to again cure the epoxy. Once the sample has cooled, cover its two sides with non-conductive epoxy so that the sample is firmly supported on the device. Then, place it back into the oven to cure the epoxy.Using an optical microscope, examine the position of the sample from all angles to check for parallel alignment of the sides of the sample with the gap. With everything now prepared, begin to apply compressive strain by rotating the micrometer screw 50 degrees while observing the surface of the sample. There should be no cracks or bending of the sample after the pressure is applied.Next, screw the device into the base plate. Once secured, apply a thin layer of silver epoxy from the base plate onto the u-shaped device to create electrical contact between the sample and the plate. Place the sample into the oven to cure the epoxy.Once cooled, check the electrical contact using a multimeter. Then, use a thin layer of non-conducting epoxy to glue an aluminum post onto the sample so that it is perpendicular to the ab cleaving plane. The posts should be the same size as the sample.When the post is correctly positioned, bake the assembled device until the epoxy is cured. First, transfer the device to the scanning tunneling microscope by placing it into the loading dock of the variable temperature, ultra-high vacuum scanning tunneling microscope. Using an arm manipulator, knock off the aluminum post in ultra-high vacuum at room temperature to expose a freshly cleaved surface.Immediately transfer the device in situ with another set of manipulators to the scanning tunneling microscope chamber, enter the microscope head, which has been cooled down to nine degrees Calvin. Allow the sample to cool down to nine degrees overnight before carrying out the next steps and maintain this temperature during the experiments. Once the temperature equilibrium has been reached, prepare the platinum iridium tips prior to each experiment by field emission on a one one one copper surface that has been treated with several rounds of sputtering and annealing.Using the voltage applied to the piezo electric materials in the microscope, move the sample stage to align with the tip. Then approach the sample. Once the tip is a few angstroms away from the sample and the tunneling current registers on the oscilloscope, it is ready for taking topographs.Here is a 10 nanometer atomic resolution topographical image of an unstrained iron tellurium single crystal. The atomic structure seen corresponds to the tellurium atoms which are exposed after cleaving the sample. The 4DA transform of the topography shows four sharp peaks at the corners of the image along the a and b directions that correspond to the atomic Bragg peaks.In contrast to the first image, this topographical image shows a topograph obtained with a magnetic tip. Unidirectional stripes with a periodicity of twice that of the lattice along the a axis are observed. The 4DA transform of this topograph shows in addition to the Bragg peaks, a new pair of satellite peaks, corresponding to half the Bragg peak momenta and therefore twice the real space wavelength.The new structure corresponds to the AFM stripe order of the iron atoms just below the surface. On some parts of the unstrained sample twin domain boundaries exist where the crystal structure with the long b axis and the accompanying AFM stripe order rotate 90 degrees. Here you can observe a 25 nanometers topograph of an AFM twin domain boundary.The 4DA transform of this region shows two pairs of AFM order highlighted by green and yellow circles. Each magnetic domain contributes to only one pair of the peaks in the 4DA transform. For the strained sample, only one single domain can be seen as a result of the uniaxial pressure applied to the sample.Here, a large-scale topography is shown spanning a total region of approximately 1.75 microns by 0.75 microns which is more than twice the total area spanned in the unstrained samples. The 4DA transform for each topograph shows only one pair of AFM peaks indicating only a single domain on this strained sample. The most important thing to consider while attempting this procedure is your ultimate goal.Knowing why you're applying uniaxial strain should guide you as to the sample orientation and how much strain to apply. Following this procedure, a strain device could also be integrated with other techniques such as x-ray diffraction, resonant elastic x-ray scattering, and angular resolved photoemission spectroscopy. SDM's a powerful technique that enables one to visualize electrons in quantum materials.And these are materials that are very sensitive to external perturbations such as strain, so the uniaxial strain integrated SDM technique will allow one to electronically tune these materials and visualize the response to strain with the ultimate goal of understanding superconductivity.

Research

JoVE Journal

Engineering

Scanning-probe Single-electron Capacitance Spectroscopy

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Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities

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Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

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Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

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Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics

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Hand Controlled Manipulation of Single Molecules via a Scanning Probe Microscope with a 3D Virtual Reality Interface

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Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

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Precision Milling of Carbon Nanotube Forests Using Low Pressure Scanning Electron Microscopy

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning ...

Demonstration of a Hyperlens-integrated Microscope and Super-resolution Imaging

The use of super-resolution imaging to overcome the diffraction limit of conventional microscopy has attracted the interest of researchers in biology and ...