W. Vincent Liu Group

Web Introduction

It hosts the online arxiv preprint selection and the schedule of group meetings and conferences for the group.

Pages are created month by month to avoid too many pages. The Monday of each week determines which month that week belongs to.

The organizer - Zehan Li - will create monthly pages and put in the readers' names routinely.

Early organizers: Bo Liu 2013-16, Xiaopeng Li 2012-13, and Zhixu Zhang 2010-12.

Group Meeting

Group meetings are scheduled on every Wednesday 7pm Pittsburgh time(Thursday 8am Beijing time) when DST starts, and every Wednesday 8pm Pittsburgh time(Thursday 8am Beijing time) when DST ends, unless noted otherwise

1. Group Meetings Schedule 2018
2. Group Meetings Schedule 2017
3. Group Meetings Schedule 2016
4. Group Meetings Schedule 2015
5. Group Meetings Schedule 2014
6. Group Meetings Schedule 2013
7. Group Meetings Schedule 2012
8. Group Meetings Schedule 2011
9. Group Meetings Schedule 2010
10. Group Meetings Schedule 2009

Arxiv Selection

The group members are expected to participate in selecting recent arxiv papers. The participants are scheduled at the beginning of each month.

1. 2018
2. 2017
3. 2016
4. 2015
5. 2014
6. 2013
7. 2012
8. 2011
9. 2010

Recent Research

1. Odd-parity topological superfluidity for fermions in a bond-centered square optical lattice We propose a physical scheme for the realization of two-dimensional topological odd-parity superfluidity in a spin-independent bond-centered square optical lattice based upon interband fermion pairing. The D4 point-group symmetry of the lattice protects a quadratic band crossing, which allows one to prepare a Fermi surface of spin-up fermions with odd parity close to the degeneracy point. In the presence of spin-down fermions with even parity populating a different energetically well-separated band, odd-parity pairing is favored. Strikingly, as a necessary prerequisite for pairing, both Fermi surfaces can be tuned to match well. As a result, topological superfluid phases emerge in the presence of merely s-wave interaction. Due to the Z2 symmetry of these odd-parity superfluids, we infer their topological features simply from the symmetry and the Fermi-surface topology as confirmed numerically.

Ref. Phys. Rev. A 96, 053607 (2017) link. https://journals.aps.org/pra/abstract/10.1103/PhysRevA.96.053607

2. Frustrated Magnetism of Dipolar Molecules on a Square Optical Lattice: Prediction of a Quantum Paramagnetic Ground State

Motivated by the experimental realization of quantum spin models of polar molecule KRb in optical lattices, we analyze the spin 1/2 dipolar Heisenberg model with competing anisotropic, longrange exchange interactions. We show that, by tilting the orientation of dipoles using an external electric field, the dipolar spin system on square lattice comes close to a maximally frustrated region similar, but not identical, to that of the J1-J2 model. This provides a simple yet powerful route to potentially realize a quantum spin liquid without the need for a triangular or kagome lattice. The ground state phase diagrams obtained from Schwinger-boson and spin-wave theories consistently show a spin disordered region between the N´eel, stripe, and spiral phase. The existence of a finite quantum paramagnetic region is further confirmed by an unbiased variational ansatz based on tensor network states and a tensor renormalization group

Ref. Phys. Rev. Lett. 119, 050401 (2017) link. https: //journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.050401 2017-08-11_8-56-43.jpg2017-08-11_8-57-12.jpg 2017-08-11_8-57-29.jpg

Group Members

Current and Former PhD Students

Lijun Lang (exchange student from Inst of Physics, Beijing; March 1, 2013 - March 4, 2014)

Xiaopeng Li (PhD Aug 2013. KITP Santa Barbara Grad Fellow, Spring term 2013. He was a postdoc in Maryland University until 2016. Now an associate professor at Fudan University, Shanghai)

Jin-Long Yu (exchange PhD student from Tsinghua University, China; Feb 1, 2013 -- July 23, 2013)

Zixu Zhang (PhD 2012. Now a physicist in finance, Morgan-Stanley, Beijing Branch)

Vladimir M. Stojanovic (advisor for his 2008 PhD from Carnegie-Mellon University. Was postdoc at U of Basel, Switzerland. Now a Swiss NSF Fellow and postdoc at Harvard physics.)

Zehan Li (Aug. 2015-)

Current and Former Postdocs

Jian-Song Pan, July 2017-- (Dr. Pan received his PhD from University of Science and Technology of China in 2017)

Biao Huang, Aug 2016-- (Dr. Huang received his PhD from Ohio State University in 2016)

Maksims "Max" Arzamasovs, Nov 2014 -- (Dr. Arzamasovs received PhD in 2014 from University of Birmingham, UK)

Ahmet Keles, Sep 2014-- ( PhD from University of Washington, Seattle; joint postdoc with Prof. Erhai Zhao, George Mason University, Fairfax, VA)

Haiyuan Zou, July 2014 -- ( Dr. Zou received PhD in 2014 from the University of Iowa )

Bo LIU, Feb 2013 -2016 in Pitt (Dr. Liu received PhD in 2013 from Peking University, China. Now he is a full professor at Xi'an Jiaotong University, Xi'an, China)

Zhifang XU, Nov 2013--2015 in Pitt (Dr. Xu received PhD in 2009 from Tsinghua U; postdoc in U of Tokyo before joining Pitt; now a Full Professor in Huazhong Univ of Science & Tech, Wuhan. China "Young 1000 Talent" Program, 2016)

Zhenyu ZHOU, Sep 2013 --2015 in Pitt(Dr. Zhou received PhD from Washington Univ in St Louis; He is a visiting scholar at Pitt/joint PostDoc with Prof. Erhai Zhao, George Mason U, Fairfax, VA)

Chungwei Lin, 2008-2011 in Pitt (Dr. Lin received PhD from Columbia University. Now postdoc at U of Texas at Austin)

Erhai Zhao, Sep 2007-Aug 2009 in Pitt (Dr. Zhao received PhD, 2005, Northwestern University, Evanston, Illinois; was postdoc associate in University of Toronto. Now Assistant Professor of physics at George Mason University, 2009-- )

Current Visiting Scholars

Yixiang Wang (Nov. 2017-)

Linghua Wen (Nov. 2017-)

Yonggang Tan (Nov. 2016-Nov 2017)

Jiemin Wang(Nov. 2016-Nov 2017)

Affiliated Members

Max Arzamasovs (joint member from WQC ZJUT Hangzhou, China)

Ahmet Keles (joint member from George Mason University, Fairfax, VA)

Yang Yang (joint member from WQC ZJUT Hangzhou, China)

Xuguang Yue (joint member from WQC ZJUT Hangzhou, China)

Other students

Hsiang-Hsuan Hung, a graduate student under "Directed Study" from May 2007--June 2008. Was a postdoc at UIUC; Now a postdoc at UT Austin)

Chiu Man Ho, PhD, 2007, Univ Pittsburgh. (Dr. Ho was a cosmology/particle physics graduate with broad interest in condensed matter theory. He was a postdoc fellow at University of California Berkeley. Now at Vanderbilt University.)

Discussion

1. Non equilibrium (Xiaopeng Li)

Recently, I got interested in non-equilibrium physics. P. Zoller's Group has a recent paper arXiv:1011.3207 [pdf, other]. They discuss non-equilibrium phase diagram of a driven-dissipative many-body system. The approach they use is the Time-Dependent Gutzwiller approach (generalized to density matrix representation). Because of the nature advantage of studying non-equilibrium physics by cold atom experiments, maybe there will be some big discovery in driven quantum many-body systems. And also a new paper ( arXiv:1011.4943 [pdf, ps, other]) by Thomas Kloss et al posted this week propose a functional renormalization group approach and they claim they can get accurate non-equilibrium time evolution of bosons even for long time. Xiaopeng's feeling is that there will be new direction studying the non-equilibrium physics in cold atom physics. (Your ideas and comments and suggestions are very welcome.)