Joseph P. Heremans is a condensed matter experimental physicist at The Ohio State University where he holds a chair as Ohio Eminent Scholar and Professor in the Department of Mechanical and Aerospace Engineering, with courtesy appointments in the Department of Physics and Department of Materials Science and Engineering. He is a member of the National Academy of Engineering. His research focuses on magneto-transport and thermal transport properties of electrons, phonons, and spin in narrow-gap semiconductors, semimetals, nanostructures, goniopolar materials, ferromagnetic and ferroelectric solids and quantum materials. Prior to OSU, Heremans worked as a research scientist and section manager at GM Research Lab from 1984-1998. From 1999-02005 he was a technical fellow at the Delphi Research Labs. He co-authored over 260 publications in refereed journals and conference proceedings. His work has garnered significant attention and has been cited more than 17,000 times, with an h-index of 58 according to ISI numbers and an h-index of 66 according to Google Scholar. He is an inventor on 40 issued US patents. He co-founded a startup company, GonioTech LLC., located in Columbus, Ohio (2019) after having been a member of the founding team of another startup, ZT Plus in Azusa, CA (2009).
Heremans was educated at the École Polytechnique de Louvain, the college of engineering of the Catholic University of Louvain (Université Catholique de Louvain) where he received a Bachelor of Science degree in electrical engineering (Ingénieur Civil Electricien) in 1975 followed by a Doctor of Applied Sciences degree (Docteur en Sciences Appliquées) in applied physics in 1978. His Ph.D. training included a Research Fellowship with the Belgian Institute for Research in Industry and Agriculture (IRSIA). Following his formal education, Prof. Heremans worked for the Fonds National de la Recherche Scientifique (FNRS, the Belgian equivalent of the French CNRS) at the École Polytechnique de Louvain and as invited postdoctoral scientist at the Oersted Institute at the University of Copenhagen, where he worked under the direction of Prof. Ole P. Hansen, a the Massachusetts Institute of Technology, where he worked under the direction of Prof. Mildred S. Dresselhaus, and at the Institute for Solid State Physics at the University of Tokyo, where he worked under the direction of Prof. Seichi Tanuma.
The research in Heremans' group involves experimental investigation of electron, magnon, and phonon transport properties. He focused on the physics of narrow-gap semiconductor (primarily InSb, PbTe, and BiSb alloys), of classical semimetals (primarily bismuth and graphite), of nanostructures (bismuth nanowires and nanostructured thermoelectric materials), of goniopolar materials (e.g. NaSn2As2 and Re4Si7) and of quantum materials, primarily Weyl semimetals (NbP, BiSb alloys) and magnetic Weyl semimetals (e.g. YbMnBi2).. His early work at GM focused on PbTe-based infrared diode lasers, InSb-based magnetic field sensors and magnetic position sensors, and carbons (e.g. he showed that molten carbon is a metal).
In the 1990s, Heremans developed the geometrical magnetoseebeck and magnetoresistance effects, the latter of which resulted in the development of magnetic field sensors [J. Phys. D: Appl. Phys. 26, 1149-1168 (1993), http://doi.org/10.1088/0022-3727/26/8/001] that went into commercial production in crankshaft and camshaft position sensors on many V6 and V8 engines made by GM for ignition timing and OBD-II misfire diagnostics .
In the early 2000s, his work switched to nanoscale thermoelectric materials for waste heat recovery applications, and also for greenhouse-gas-free refrigeration. His work on quantum wires resulted in the discovery of large thermopowers due to size-quantization effects [Phys. Rev. B 61, 2921 (2000) http://doi.org/10.1103/PhysRevB.61.2921]. In 2008, his team published evidence that resonant levels increase the thermoelectric figure of merit, zT, in PbTe by distorting the electronic density of states [ Science 321, 554 -558 (2008) http://dx.doi.org/10.1126/science.1159725 . This and other discoveries provided the basis for the foundation of ZT Plus.
Research on spin caloritronic effects [Energy Environ. Sci., 7, 885-910 (2014) http://dx.doi.org/10.1039/C3EE43299H] was added to his portfolio around 2010, first on GaMnAs [Nature Materials 9 898-903 (2010) http://doi.org/10.1038/nmat2860]. In 2012, his team published data proving the giant spin-Seebeck effect in a non-magnetic material; they demonstrated that the spin-Seebeck effect in InSb is as large as the largest thermopower values ever measured [Nature 487, 210-213 (2012) http://dx.doi.org/10.1038/nature11221]. He also identifies magnon-drag as a spin-caloritronic effect; this is a phenomenon by which thermal gradients create a spin flux that then drags along an electron flux, giving rise to a strong enhancement of the Seebeck coefficient. This opens a new physical mechanism to optimize thermoelectric materials. This mechanism even works with paramagnons, damped magnons that exist locally in paramagnets above the ordering temperature [Science Advances, eaat9461, (2019) http://doi.org/10.1126/sciadv.aat9461].
In 2015, his team published experimental proof that phonons in diamagnets respond to magnetic fields.[Nature Materials 14, 601-606 (2015) http://dx.doi.org/10.1038/nmat4247 ] This is extended in 2023 with investigations of the nature of the thermal perturbations of the ferroelectric order in ferroelectrics being added to the research portfolio [Science Advances 9, eadd7194 (2023); https://doi.org/10.1126/sciadv.add7194 ]. This is a new field where much is still unknown but that offers potential control of phonon behavior with electrical and magnetic fields, with potential applications in new memory and logic devices, and in thermal switches.
Investigations of quantum materials is added to his research portfolio in 2017. He outlines the difficulties in obtaining truly electrically insulating topological insulators.[ Nature Reviews Materials 2 17049 (2017) http://doi.org/10.1038/natrevmats.2017.49 ] He adds studies on Weyl semimetals like NbP and identifies the thermal chiral anomaly in 2021 [Nature Materials 20,1525–1531 (2021) http://doi.org/10.1038/s41563-021-00983-8 ].
In 2019, he and several colleagues developed goniopolar materials, materials that, due to the specific shape and topology of their Fermi surface, display simultaneous n- and p-type behavior of the same charge carriers, depending on the direction and type of measurement.[Nature Materials. 18 568-572 (2019) http://doi.org/10.1038/s41563-019-0309-4]. These materials have applications in transverse thermoelectric generators [Energy and Environmental Science 14, 4009-4017 (2021) http://doi.org/10.1039/D1EE00923K] and non-reciprocal microwave devices. This latter property provided the basis for the foundation of GonioTech LLC.
Honors and awards
In 1987, Heremans was named fellow of the American Physical Society for his pioneering work in the thermal conductivity of low-dimensional materials and electronic magnetostriction; and for the study of electronic and thermal properties of narrow-gap semiconductors, semimetals, and graphite intercalation compounds. In 2011, he was named fellow of American Association for the Advancement of Science, and he was elected to the National Academy of Engineering in 2013 for his discoveries in thermal energy transfer and conversion to electricity, and for the commercial devices employed in automobiles.
Heremans has won several awards at OSU: the Clara M. and Peter L. Scott Award for Excellence in Engineering Education (2014), the Lumley Interdisciplinary Research Award (2013, 2019), the Lumley Award (2010), the Innovators Award (2010), and OSU’s the Inventor of the Year Award (2011). He won a regional award, the TechColumbus Inventor of the Year award (2009). At General Motors he was the recipient of the Charles L. McCuen Award (1994), the John M. Campbell Award (1989) and the Boss Kettering Award (1994), which recognizes an invention that has seen commercial production. At Delphi he was elected to the Inventors Hall of Fame (1999), Gold Level (2004), and won the Scientific Excellence Award (2003).
Experimental investigation of electron, phonon and spin transport properties, semiconductor, semimetals, topological and magnetic materials and nanostructures. Contributions:
- Goniopolar materials exhibit simultaneous n- and p-type behavior by the same charge carriers (2019). They enable the construction of transverse thermoelectric generators that don't need electrical contacts at their hot side, and mostly eliminate efficiency losses in contact resistances (2021).
- Phonons in diamagnets respond to magnetic fields (2015). Phonons in ferroelectric materials can also be affected by an external electric field (2023). This discovery constitutes the base of a new approach to electrical control of the lattice thermal conductivity. This new field is labeled "polarization caloritronics".
- The thermal chiral anomaly is a new way for electrons to carry heat. This process applies only to electrons in Weyl semimetals, in which electrons are massless but have a "chirality". In the presence of a temperature gradient, energy (heat) is created by electrons of one chirality, annihilated by electrons of opposite chirality, and this creates a heat transfer mechanism, grounded in quantum mechanics, that dominates all other mechanisms (2021). It offers the possibility of realizing all-solid-state heat switches.
- In 2008, a new field, labeled spin caloritronics, opened that linked the transport of heat by magnons (the thermal perturbations of the ferromagnetic order) to the transport of spin. We contributed to this field, e.g. by identifying the giant spin-Seebeck effect in InSb is as large as the largest thermopower values measured (2012). Another discovery is that magnons can drag electrons in a phenomenon labeled magnon-drag, and this in turn can contribute greatly to boost the Seebeck coefficients of magnetic materials. Even in the paramagnetic state, paramagnons can drag electrons (2017), boosting the thermoelectric figure of merit.
- Resonant levels increase the thermoelectric figure of merit (2008).
- Large thermopowers in quantum wires due to size-quantization (2002-4)
- Geometrical magnetoseebeck and magnetoresistance effects – the latter resulted in commercial position sensors used on crank and camshafts by GM (1990s).