Colloquium - Nitin Samarth (Penn State University) - Topolgical Spintronics: from the Haldan Phase to Spin Devices

Nitin Samarth (Penn State) 9/25/18 Colloquium speaker

September 25, 2018

3:45PM - 4:45PM

1080 Physics Research Building - Smith Seminar Room - reception at 3:30 pm in the Atrium

Add to Calendar 2018-09-25 15:45:00 2018-09-25 16:45:00 Colloquium - Nitin Samarth (Penn State University) - Topolgical Spintronics: from the Haldan Phase to Spin Devices We provide a perspective on the recent emergence of “topological spintronics,” which relies on helical Dirac electrons on the surfaces of solids with strong spin-orbit coupling [1]..When timereversal symmetry is broken by ferromagnetic order, the helical Dirac states transition to chiral edge states [2]. This is a realization of Haldane’s Chern insulator phase of matter, characterized by a precisely quantized Hall conductance and ballistic edge transport without a magnetic field, even in systems with significant electronic and magnetic disorder [3,4]. The interplay between these edge states, dissipative channels and magnetic order appears to yield a condensed matter realization of quantum tunneling out of a ‘false vacuum’ [4]. Interesting opportunities are also emerging for patterning and manipulating the edge states using optical techniques [5]. On a more pragmatic note, the helical spin texture of the surface states also leads to efficient spincharge conversion at room temperature [6,7], allowing one to envision novel devices for universal memory and spin-based logic. [1] M. Neupane, A. Richardella et al., Nature Communications 5, 3841 (2014).[2] A. Kandala, A. Richardella, et al., Nature Communications 6, 7434 (2015).[3] E. Lachman et al., Science Advances 1, e1500740 (2015).[4] M. Liu et al., Science Advances 2, e1600167 (2016).[5] A. L. Yeats et al. PNAS (online 12 September, 2017).[6] A. Mellnik, J. S. Lee, A. Richardella et al., Nature 511, 449 (2014).[7] H. Wang et al., Physical Review Letters 117, 076601 (2016). 1080 Physics Research Building - Smith Seminar Room - reception at 3:30 pm in the Atrium OSU ASC Drupal 8 ascwebservices@osu.edu America/New_York public

Add to Calendar 2018-09-25 15:45:00 2018-09-25 16:45:00 Colloquium - Nitin Samarth (Penn State University) - Topolgical Spintronics: from the Haldan Phase to Spin Devices We provide a perspective on the recent emergence of “topological spintronics,” which relies on helical Dirac electrons on the surfaces of solids with strong spin-orbit coupling [1]..When timereversal symmetry is broken by ferromagnetic order, the helical Dirac states transition to chiral edge states [2]. This is a realization of Haldane’s Chern insulator phase of matter, characterized by a precisely quantized Hall conductance and ballistic edge transport without a magnetic field, even in systems with significant electronic and magnetic disorder [3,4]. The interplay between these edge states, dissipative channels and magnetic order appears to yield a condensed matter realization of quantum tunneling out of a ‘false vacuum’ [4]. Interesting opportunities are also emerging for patterning and manipulating the edge states using optical techniques [5]. On a more pragmatic note, the helical spin texture of the surface states also leads to efficient spincharge conversion at room temperature [6,7], allowing one to envision novel devices for universal memory and spin-based logic. [1] M. Neupane, A. Richardella et al., Nature Communications 5, 3841 (2014). [2] A. Kandala, A. Richardella, et al., Nature Communications 6, 7434 (2015). [3] E. Lachman et al., Science Advances 1, e1500740 (2015). [4] M. Liu et al., Science Advances 2, e1600167 (2016). [5] A. L. Yeats et al. PNAS (online 12 September, 2017). [6] A. Mellnik, J. S. Lee, A. Richardella et al., Nature 511, 449 (2014). [7] H. Wang et al., Physical Review Letters 117, 076601 (2016). 1080 Physics Research Building - Smith Seminar Room - reception at 3:30 pm in the Atrium Department of Physics physics@osu.edu America/New_York public

We provide a perspective on the recent emergence of “topological spintronics,” which relies on helical Dirac electrons on the surfaces of solids with strong spin-orbit coupling [1]..When timereversal symmetry is broken by ferromagnetic order, the helical Dirac states transition to chiral edge states [2]. This is a realization of Haldane’s Chern insulator phase of matter, characterized by a precisely quantized Hall conductance and ballistic edge transport without a magnetic field, even in systems with significant electronic and magnetic disorder [3,4]. The interplay between these edge states, dissipative channels and magnetic order appears to yield a condensed matter realization of quantum tunneling out of a ‘false vacuum’ [4]. Interesting opportunities are also emerging for patterning and manipulating the edge states using optical techniques [5]. On a more pragmatic note, the helical spin texture of the surface states also leads to efficient spincharge conversion at room temperature [6,7], allowing one to envision novel devices for universal memory and spin-based logic.

[1] M. Neupane, A. Richardella et al., Nature Communications 5, 3841 (2014).

[2] A. Kandala, A. Richardella, et al., Nature Communications 6, 7434 (2015).

[3] E. Lachman et al., Science Advances 1, e1500740 (2015).

[4] M. Liu et al., Science Advances 2, e1600167 (2016).

[5] A. L. Yeats et al. PNAS (online 12 September, 2017).

[6] A. Mellnik, J. S. Lee, A. Richardella et al., Nature 511, 449 (2014).

[7] H. Wang et al., Physical Review Letters 117, 076601 (2016).