Clemson University

Colloquium: Dr. Cheng-Chien Chen, University of Alabama at Birmingham

Colloquium

Department of Physics and Astronomy

Thursday, August 26, 4:00 pm

G01 Kinard Lab

Refreshments served after the colloquium in the PandA Café

 

Thermoelectric and Topological Properties of

Lanthanum Monopnictides under Pressure

 

Dr. Cheng-Chien Chen

Department of Physics, University of Alabama at Birmingham

Uniaxial strain and hydrostatic pressure are effective tools in engineering quantum materials [1]. Here, we first study rock-salt structured lanthanum monopnictides LaX (X = P, As) using density functional theory [2]. Under 2% tensile strain and carrier concentration n = 3 × 1020 cm−3, we show that LaP at 1200 K can achieve a figure of merit ZT value > 2, which is enhanced by 90% compared to the unstrained value. In contrast, the rock-salt structure of LaN is found dynamically unstable at zero temperature [3]. Using evolutionary crystal prediction, we discover a dynamically stable P1 structure with spontaneous electric polarization. Ab initio molecular dynamics simulations suggest that P1-LaN will undergo ferroelectric and structural transitions at elevated temperature. Under ~14-18 GPa external pressure, LaN can further show simultaneous temperature-induced structural, ferroelectric, and topological transitions. Lanthanum monopnictides thereby provide a rich playground for exploring novel quantum phases and phase transitions.

References

[1] J. Mutch et al., “Evidence for a strain-tuned topological phase transition in ZrTe5”, Science Advances 5, eaav9771 (2019).

[2] C.-M. Lin, W.-C. Chen, and C.-C. Chen, “First-principles study of strain effect on the thermoelectric properties of LaP and LaAs”, Phys. Chem. Chem. Phys. (2021).

[3] W.-C. Chen, C.-M. Lin, J. Maciejko, and C.-C. Chen, “LaN Structural and Topological Transitions Driven by Temperature and Pressure”, arXiv:2104.12879 (2021).

 

Bio: Dr. Cheng-Chien Chen received a Ph.D. in Physics from Stanford University in 2011. Afterward, he became a Postdoctoral Scholar at SLAC National Accelerator Laboratory and later an Aneesur Rahman Postdoctoral Fellow at Argonne National Laboratory. He joined the Department of Physics at the University of Alabama at Birmingham as an Assistant Professor in 2016. Dr. Chen’s expertise lies in using quantum many-body simulations, first-principles calculations, and machine learning approaches to model and discover various quantum and functional materials. His research topics have been funded by NSF Office of Integrative Activities (OIA), Office of Advanced Cyberinfrastructure (OAC), and the Metals and Metallic Nanostructures (MMN) Program, as well as more recently by Air Force Office of Scientific Research (AFOSR).

 

Thursday, August 26, 2021 at 4:00pm to 5:00pm

Kinard Laboratory of Physics, G01
140 Delta Epsilon Ct., Clemson, SC 29634, USA

Event Type

Lectures / Seminars / Speakers

Target Audience

Faculty, Students, Undergraduate, Graduate, Postdocs

Departments

College of Science, Physics and Astronomy

Contact Name:

Kim Webb

Contact Phone:

8646563416

Contact Email:

kwebb4@clemson.edu

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