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【TDLI】Important Progress in the Study of Strongly Correlated Magnetic Compound

April 28, 2021      Author:

Tsung-Dao Lee Fellow Chi Ming Yim et al. have made important progress in the study of strongly correlated magnetic compound iron telluride, with the related research results published as a research article entitled "Strain-Stabilized (π, π) Order at the Surface of Fe1+xTe " in Nano Letters.

The interplay between magnetism and superconductivity has always been a common theme in the research of iron-based superconductors.  Most iron-based superconductors with zero doping exhibit a magnetic order characterized by a wavevector of (π, π).  As doping level increases, magnetic order of this kind gets suppressed, and superconductivity sets in.  This universal behavior also implies the importance of magnetic fluctuation to superconductivity.  However, this universality is not applicable to iron-chalcogenides, among which iron telluride (Fe1+xTe) exhibits magnetic order along the (π, 0) direction, while superconducting iron selenide does not show any magnetic order.  The discrepancy in magnetic order may also be reflected from the different crystal structure of Fe1+xTe .

Figure 1 (a, b) (π, π) and (π, 0) surface magnetic orders in iron pnictide and chalcogenide compounds. (c) Calculated formation energies of the two magnetic orders at different strain values.  (d) Schematic of STM-strain setup.  Different thermal expansion properties between the sample and piezoelectric actuator leads to tensile strain in the sample after cooling.  (e) STM image of unstrained Fe1+xTe sample. (f) Magnetic image taken within one monoclinic domain.  Inset (bottom-right): Fourier transform image of (f).  Inset (top-left): non-magnetic, atomically resolved image.

This work employed uniaxial strain and low temperature scanning tunneling microscopy to tune and measure the ground-state of Fe1+x Te.  Experimental results show that by applying uniaxial pressure along the <110> direction to the crystal, the surface of Fe1.1Te undergoes (π, 0) magnetic order to (π, π) charge order transition.  Results from transport measurements also performed with uniaxial strain show that the observed (π, π) ordered phase is a surface phase.  This work offers new opportunities for the exploration for novel electronic phases stabilized near the surface and interface.

Figure 2. (a) STM image of the (π, π) ordered phase of strained Fe1.1Te. (b) Atomically resolved image of the (π, π) ordered phase.  (c) Fourier transform image of (b).  Black and red circles mark the crystal Bragg peaks and the (π, π) order peaks respectively.

Research collaborators of this work include Prof. Peter Wahl group, Dr. Andreas Rost group, and Dr. Alexandra Gibbs of University of St. Andrews (UK), Dr. Christoph Heil of Graz University of Technology (Austria), Dr. Oxana Magdysyuk of Diamond Light Source (UK), and Prof. Alois Loidl and Dr. Vladimir Tsurkan of University of Augsburg.  T. D. Lee Fellow Prof. Chi Ming Yim is the first author and co-corresponding author with Prof. Peter Wahl.

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Source: Tsung-Dao Lee Institute