Title: Magnetic field-induced non-trivial electronic topology in Fe_3-xGeTe₂

Abstract

The anomalous Hall, Nernst, and thermal Hall coefficients of the itinerant ferromagnet Fe_3-xGeTe₂ display anomalies upon cooling that are consistent with a topological transition that could induce deviations with respect to the Wiedemann–Franz (WF) law. This law has not yet been validated for the anomalous transport variables, with recent experimental studies yielding material-dependent results. Nevertheless, the anomalous Hall and thermal Hall coefficients of Fe_3-xGeTe₂ are found, within our experimental accuracy, to satisfy the WF law for magnetic fields ${\mu }_{0}H$ applied along its c axis. Remarkably, large anomalous transport is also observed for ${\mu }_{0}H\left|\right|a$ axis with the field aligned along the gradient of the chemical potential generated by thermal gradients or electrical currents, a configuration that should not lead to their observation. These anomalous planar quantities are found to not scale with the component of the planar magnetization ( $M_{\left|\right|}$), showing instead a sharp decrease beyond ${\mu }_0{H}_{\left|\right|}=$ 4 T or the field required to align the magnetic moments along ${\mu }_{0}H$_||. We argue that chiral spin structures associated with Bloch domain walls lead to a field-dependent spin chirality that produces a novel type of topological transport in the absence of interaction between the magnetic field and electrical or thermal currents. Locally chiral spin structures are captured by our Monte Carlo simulations incorporating small Dzyaloshinskii–Moriya and biquadratic exchange interactions. These observations reveal not only a new way to detect and expose topological excitations, but also a new configuration for heat conversion that expands the current technological horizon for thermoelectric energy applications.

Authors:

Macy, Juan  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-7624-4843"

Ratkovski, Danilo  ^[1];

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Balakrishnan, Purnima P.  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-1426-669X"

Strungaru, Mara ^[3]; Chiu, Yu-Che ^[1]; Flessa Savvidou, Aikaterini ^[1]; Moon, Alex ^[1]; Zheng, Wenkai ^[1]; Weiland, Ashley  ^[4];

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McCandless, Gregory T. ^[4]; Chan, Julia Y.  ^[4];

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Kumar, Govind S. ^[5]; Shatruk, Michael ^[5]; Grutter, Alexander J.  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-6876-7625"

Borchers, Julie A. ^[2]; Ratcliff, William D.  ^[2];

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Choi, Eun Sang ^[1]; Santos, Elton G.  ^[6];

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• Search DOE PAGES for ORCID "0000-0001-6065-5787"

Balicas, Luis  ^[1]

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• Search DOE PAGES for ORCID "0000-0002-5209-0293"

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+ Show Author Affiliations

1. Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab)
2. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research
3. Univ. of Edinburgh, Scotland (United Kingdom). Institute for Condensed Matter Physics and Complex Systems
4. Univ. of Texas at Dallas, Richardson, TX (United States)
5. Florida State Univ., Tallahassee, FL (United States)
6. Univ. of Edinburgh, Scotland (United Kingdom). Institute for Condensed Matter Physics and Complex Systems, and Higgs Centre for Theoretical Physics

Publication Date:

Thu Oct 07 00:00:00 EDT 2021

Research Org.:

Florida State Univ., Tallahassee, FL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF); Engineering and Physical Sciences Research Council (EPSRC); University of Edinburgh

OSTI Identifier:

1825055

Alternate Identifier(s):

OSTI ID: 1824719

Grant/Contract Number:  

SC0002613; EP/P020194/1; EP/P020267/1; EP/T021578/1

Resource Type:

Accepted Manuscript

Journal Name:

Applied Physics Reviews

Additional Journal Information:

Journal Volume: 8; Journal Issue: 4; Journal ID: ISSN 1931-9401

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY