Turan Birol
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Turan Birol has a total of 471 co-authors. Here are the top co-authors by number of shared publications:
- Rafael M. Fernandes
School of Physics and Astronomy, University of Minnesota, Minneapolis, USA
15 shared publications - Chris Leighton
Department of Chemical Engineering and Materials Science University of Minnesota Minneapolis Minnesota USA
9 shared publications Arpita Paul
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
8 shared publicationsEthan T. Ritz
Department of Chemical Engineering and Materials Science University of Minnesota 55455 Minneapolis MN USA
7 shared publications- Janice L. Musfeldt
Department of Chemistry, University of Tennessee 1 , Knoxville, Tennessee 37996
7 shared publications - K. Andre Mkhoyan
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
7 shared publications
Latest Publications
- 9 November 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 114 (28)
Tuning charge transport properties and magnetic order in metallic EuTi O 3 − δ
- 9 November 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 114 (28)
Tuning charge transport properties and magnetic order in metallic EuTi O 3 − δ
- 28 September 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 114 (14) , 144108
Ferroic polarization from nonpolar phonons
The Born effective charge, a fundamental quantity in lattice dynamics and ferroelectrics, provides a quantitative measure of the linear polarization response to ionic displacements. However, it does not account for higher-order effects, which can play a significant role in certain materials, such as fluorite ${\mathrm{HfO}}_{2}$. In this paper, we use the second-order mode effective charges defined with the second-order atomic dynamical charges as a measure of the dipole moments generated by nonpolar lattice distortions. Using first-principles calculations, we demonstrate that specific combinations of nonpolar phonons in many oxides can induce strongly aligned second-order polarizations, reaching magnitudes comparable to those of intrinsically polar modes even in the zero-frequency limit, broadening the understanding of second-order effects, which have historically been emphasized for their dynamical effects at specific frequency ranges. Through a symmetry-based analysis of the charge density, we elucidate the microscopic origin of these effects, tracing them to variations in bond covalency and local electronic rearrangements. We also demonstrate large second-order mode effective charge in well-studied perovskites, highlighting the generality of these phenomena. Our results offer insights into the design principles of next-generation ferroelectric, piezoelectric, and multifunctional materials from the higher-order contribution to polarization in crystalline solids.- 28 September 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 114 (14) , 144108
Ferroic polarization from nonpolar phonons
The Born effective charge, a fundamental quantity in lattice dynamics and ferroelectrics, provides a quantitative measure of the linear polarization response to ionic displacements. However, it does not account for higher-order effects, which can play a significant role in certain materials, such as fluorite ${\mathrm{HfO}}_{2}$. In this paper, we use the second-order mode effective charges defined with the second-order atomic dynamical charges as a measure of the dipole moments generated by nonpolar lattice distortions. Using first-principles calculations, we demonstrate that specific combinations of nonpolar phonons in many oxides can induce strongly aligned second-order polarizations, reaching magnitudes comparable to those of intrinsically polar modes even in the zero-frequency limit, broadening the understanding of second-order effects, which have historically been emphasized for their dynamical effects at specific frequency ranges. Through a symmetry-based analysis of the charge density, we elucidate the microscopic origin of these effects, tracing them to variations in bond covalency and local electronic rearrangements. We also demonstrate large second-order mode effective charge in well-studied perovskites, highlighting the generality of these phenomena. Our results offer insights into the design principles of next-generation ferroelectric, piezoelectric, and multifunctional materials from the higher-order contribution to polarization in crystalline solids.- 23 September 2026
- Published by American Physical Society (APS) in Physical Review Materials
- Vol. 10 (9)
Decoupling the high-temperature spin-state and insulator-metal transitions in LaCo O 3 via heteroepitaxial strain
- 23 September 2026
- Published by American Physical Society (APS) in Physical Review Materials
- Vol. 10 (9)
Decoupling the high-temperature spin-state and insulator-metal transitions in LaCo O 3 via heteroepitaxial strain
- 8 September 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 114 (15) , 154407
All-in-all-out pyrochlore iridates as noncollinear spin-orbit coupled counterparts of altermagnets
Altermagnets are collinear magnetically ordered states that exhibit momentum-dependent spin splitting in the absence of net magnetization and spin-orbit coupling (SOC). Related spin-splitting patterns, however, can also emerge in noncollinear magnetic systems with large SOC. Here we show, via a microscopic model, that the all-in-all-out (AIAO) state in pyrochlore iridates constitutes a noncollinear counterpart of a $d$-wave altermagnet stabilized by strong SOC. Starting from a microscopic ${j}_{\mathrm{eff}}=\frac{1}{2}$ tight-binding model on the pyrochlore lattice, we demonstrate that electronic interactions favor the AIAO phase and analyze its symmetry properties. We show that the AIAO order parameter transforms as an ${A}_{2g}^{\ensuremath{-}}$ octupolar magnetic moment, breaking time-reversal symmetry while preserving inversion and zero net magnetization. Using group-theory analysis and mean-field calculations, we demonstrate that this symmetry enforces both a spin-polarized momentum-dependent lifting of band degeneracies that is similar to that of a collinear $d$-wave cubic altermagnet, but also a band splitting at zero momentum. We show that the latter feature is captured by a low-energy model similar to the Luttinger-Kohn model for cubic semiconductors. Our results identify pyrochlore iridates as a platform for noncollinear counterparts of altermagnetism and provide a general symmetry framework for spin-split phenomena in spin-orbit coupled materials.- 8 September 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 114 (15) , 154407
All-in-all-out pyrochlore iridates as noncollinear spin-orbit coupled counterparts of altermagnets
Altermagnets are collinear magnetically ordered states that exhibit momentum-dependent spin splitting in the absence of net magnetization and spin-orbit coupling (SOC). Related spin-splitting patterns, however, can also emerge in noncollinear magnetic systems with large SOC. Here we show, via a microscopic model, that the all-in-all-out (AIAO) state in pyrochlore iridates constitutes a noncollinear counterpart of a $d$-wave altermagnet stabilized by strong SOC. Starting from a microscopic ${j}_{\mathrm{eff}}=\frac{1}{2}$ tight-binding model on the pyrochlore lattice, we demonstrate that electronic interactions favor the AIAO phase and analyze its symmetry properties. We show that the AIAO order parameter transforms as an ${A}_{2g}^{\ensuremath{-}}$ octupolar magnetic moment, breaking time-reversal symmetry while preserving inversion and zero net magnetization. Using group-theory analysis and mean-field calculations, we demonstrate that this symmetry enforces both a spin-polarized momentum-dependent lifting of band degeneracies that is similar to that of a collinear $d$-wave cubic altermagnet, but also a band splitting at zero momentum. We show that the latter feature is captured by a low-energy model similar to the Luttinger-Kohn model for cubic semiconductors. Our results identify pyrochlore iridates as a platform for noncollinear counterparts of altermagnetism and provide a general symmetry framework for spin-split phenomena in spin-orbit coupled materials.- 27 August 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 114 (10) , 105142
Symmetries of spin splitting induced by spin-orbit coupling in nonmagnetic crystals
Spin-orbit coupling (SOC) leads to splitting of otherwise spin-degenerate bands in noncentrosymmetric materials, even if time-reversal symmetry is present. While this gives rise to well-known phenomena such as the Rashba and Dresselhaus effects, various other terms are allowed based on the point group of the crystal and the electronic Hamiltonian. In this study, we utilize point group representations to illustrate that four different types of SOC terms (Rashba, Dresselhaus, Weyl, and Ising) can emerge in periodic solids. We construct reciprocal-space energy expressions for each type of SOC-induced splitting of opposite-spin bands, and follow a similar procedure to also obtain minimal tight-binding models that capture all types of spin splittings for subgroups of two high-symmetry groups $m\overline{3}m$ and $6/mmm$. Furthermore, we also obtain a complete list of nodal features in the electronic band structure in these systems, distinguishing between crystallographic-symmetry-imposed nodal lines and those imposed by time-reversal symmetry only. Finally, we conclude by presenting a list of materials that host each type of inversion-breaking SOC effects. Our classification of the spin-splitting symmetries in nonmagnetic systems with SOC is the counterpart of the recent classification of spin-splitting symmetries in unconventional magnetic systems without SOC, such as altermagnets and odd-parity magnets. More broadly, our work provides a basis for studying superconductivity and other collective electronic phenomena that are impacted by SOC-induced band splittings in noncentrosymmetric materials.- 27 August 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 114 (10) , 105142
Symmetries of spin splitting induced by spin-orbit coupling in nonmagnetic crystals
Spin-orbit coupling (SOC) leads to splitting of otherwise spin-degenerate bands in noncentrosymmetric materials, even if time-reversal symmetry is present. While this gives rise to well-known phenomena such as the Rashba and Dresselhaus effects, various other terms are allowed based on the point group of the crystal and the electronic Hamiltonian. In this study, we utilize point group representations to illustrate that four different types of SOC terms (Rashba, Dresselhaus, Weyl, and Ising) can emerge in periodic solids. We construct reciprocal-space energy expressions for each type of SOC-induced splitting of opposite-spin bands, and follow a similar procedure to also obtain minimal tight-binding models that capture all types of spin splittings for subgroups of two high-symmetry groups $m\overline{3}m$ and $6/mmm$. Furthermore, we also obtain a complete list of nodal features in the electronic band structure in these systems, distinguishing between crystallographic-symmetry-imposed nodal lines and those imposed by time-reversal symmetry only. Finally, we conclude by presenting a list of materials that host each type of inversion-breaking SOC effects. Our classification of the spin-splitting symmetries in nonmagnetic systems with SOC is the counterpart of the recent classification of spin-splitting symmetries in unconventional magnetic systems without SOC, such as altermagnets and odd-parity magnets. More broadly, our work provides a basis for studying superconductivity and other collective electronic phenomena that are impacted by SOC-induced band splittings in noncentrosymmetric materials.- 14 August 2026
- Published by American Physical Society (APS) in Physical Review Materials
- Vol. 10 (7)
Structural distortions and ferroelectricity in antiperovskite oxides with tetrel elements
- 14 August 2026
- Published by American Physical Society (APS) in Physical Review Materials
- Vol. 10 (7)
Structural distortions and ferroelectricity in antiperovskite oxides with tetrel elements
- Open Access
- 31 July 2026
- Published by American Association for the Advancement of Science (AAAS) in Science Advances
- Vol. 12 (31) , eaec2917
Observation of mirror-odd and mirror-even spin texture in ultrathin epitaxially strained RuO 2 films
Recently, rutile ruthenium dioxide (RuO 2 ) has attracted renewed interest due to expectations of prominent altermagnetic spin splitting. However, accumulating experimental evidence suggests that, in its bulk and thick-film forms, RuO 2 does not display any form of magnetic ordering. Despite this, the spin structure of RuO 2 remains largely unexplored in the ultrathin limit, where substrate-imposed epitaxial strain can be substantial. Here, we use spin-resolved angle-resolved photoemission spectroscopy, supported by ab initio calculations, to reveal the electronic structure of 2-nanometer-thick epitaxial RuO 2 heterostructures. We observe an unconventional spin texture characterized by the coexistence of mirror-even and mirror-odd momentum-dependent components. A comprehensive symmetry analysis rules out nonmagnetic origins of this spin texture. These findings suggest an emergent nonrelativistic spin structure enabled by epitaxial strain in the ultrathin limit, marking a distinct departure from the behavior of relaxed or bulk RuO 2 . Our work opens previously unexplored perspectives for exploring symmetry-breaking mechanisms and spin textures in oxide heterostructures.
- 31 July 2026
- Published by American Association for the Advancement of Science (AAAS) in Science Advances
- Vol. 12 (31) , eaec2917
Open AccessObservation of mirror-odd and mirror-even spin texture in ultrathin epitaxially strained RuO 2 films
Recently, rutile ruthenium dioxide (RuO 2 ) has attracted renewed interest due to expectations of prominent altermagnetic spin splitting. However, accumulating experimental evidence suggests that, in its bulk and thick-film forms, RuO 2 does not display any form of magnetic ordering. Despite this, the spin structure of RuO 2 remains largely unexplored in the ultrathin limit, where substrate-imposed epitaxial strain can be substantial. Here, we use spin-resolved angle-resolved photoemission spectroscopy, supported by ab initio calculations, to reveal the electronic structure of 2-nanometer-thick epitaxial RuO 2 heterostructures. We observe an unconventional spin texture characterized by the coexistence of mirror-even and mirror-odd momentum-dependent components. A comprehensive symmetry analysis rules out nonmagnetic origins of this spin texture. These findings suggest an emergent nonrelativistic spin structure enabled by epitaxial strain in the ultrathin limit, marking a distinct departure from the behavior of relaxed or bulk RuO 2 . Our work opens previously unexplored perspectives for exploring symmetry-breaking mechanisms and spin textures in oxide heterostructures.
- 30 June 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 114 (9)
Interplay between charge correlations and superconductivity across the superconducting domes of CsV 3 Sb ( 5 − x ) Sn x
- 30 June 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 114 (9)
Interplay between charge correlations and superconductivity across the superconducting domes of CsV 3 Sb ( 5 − x ) Sn x
- Open Access
- 16 June 2026
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 137 (5)
Probing multipolar order in the candidate altermagnet MnF 2 through the elastocaloric effect under strain
Altermagnets break a combination of time-reversal and rotational symmetries without generating a net magnetization. As such, the order parameter of d -wave altermagnets has the same symmetry as magnetic multipoles and couples to the product of a magnetic field and uniaxial strain. We combine elastocaloric experiments, free-energy modeling, and first-principles calculations on MnF 2 to establish a thermodynamic probe of the predicted finite-temperature altermagnetic critical point. These results pave the way to explore altermagnetic quantum criticality in d -wave materials and beyond.
- 16 June 2026
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 137 (5)
Open AccessProbing multipolar order in the candidate altermagnet MnF 2 through the elastocaloric effect under strain
Altermagnets break a combination of time-reversal and rotational symmetries without generating a net magnetization. As such, the order parameter of d -wave altermagnets has the same symmetry as magnetic multipoles and couples to the product of a magnetic field and uniaxial strain. We combine elastocaloric experiments, free-energy modeling, and first-principles calculations on MnF 2 to establish a thermodynamic probe of the predicted finite-temperature altermagnetic critical point. These results pave the way to explore altermagnetic quantum criticality in d -wave materials and beyond.
- 10 June 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 113 (21)
Orbital altermagnetism on the kagome lattice and possible application to A V 3 Sb 5
- 10 June 2026
- Published by American Physical Society (APS) in Physical Review B
- Vol. 113 (21)
Orbital altermagnetism on the kagome lattice and possible application to A V 3 Sb 5