Here we present some of the research topics I am interested in. Each research topic has its own small webpage with more information.
I. Magnetic Skyrmions and Hall Transport :
Magnetic Skyrmions are topological objects (protected by a topological number and an energy gap and robust under disturbances) that have been originally proposed in high energy theory, yet recently observed in real condensed matter systems. They have a viable application as a next generation storage devices and have been actively studied theoretically and experimentally. Due to extended nature of the Skyrmions, most of the studies rely on phenomenological models. We studied the Hall transport of the Skyrmion systems using Ward identities by utilizing the central extension of the momentum-momentum commutation relations as well as conservation equations. We propose a simple and clear ways to measure mysterious Hall viscosity. For more details, visit Magnetic Skyrmions and Hall Transport site.
II. Entanglement Entropy and Background Gauge Fields :
Entanglement entropy is useful for measuring quantum information and has been extensively studied recently. We consider the entropy in the presence of background gauge fields, such as electric and magnetic fields, that can manipulate quantum fields. We have provided a general formula for the entropies that can be applied in the presence of the background gauge fields. With this formula, we investigated various properties of the entropies to find interesting results. For more details, visit Entanglement entropy in the presence of background field site.
III. Lifshitz Hydrodynamics and Quantum Critical Point :
Hydrodynamics is an effective theory describing physics at large space and long time scale and incorporates dissipative effects based on symmetries. This captures universal features. Recently, there have been exciting progresses in Hydrodynamics when parity and boost symmetries are broken. When boost symmetry is broken, there exist non-diagonal components of the stress energy tensor. We uncovered one new transport coefficient in the first order of derivative expansion in the neutral Hydrodynamics and two additional transport coefficients in the charged Hydrodynamics. For more details, visit Hydrodynamics and Quantum Criticality site.
IV. Holographic Model for a Quantum Critical Point :
Understanding the phase diagram of the high Tc superconductor has been one of the major research topics in Condensed matter physics. If the superconducting dome is removed by a high magnetic field or chemical doping, one can measure various transport properties of the underlying high Tc materials. Universal temperature dependences of magneto-transports in optimal and over doped phases of high Tc cuprates, like resistivity, inverse Hall angle and Hall coefficients, are in good agreement with a holographic model with Schroedinger symmetry. For more details, visit Holographic Model for a Quantum Critical Point site.
V. Holography, Quantum field theory and String theory :
String theory aspires to unify the four fundamental interactions of nature. Despite various successes, the theory has yet to bring relevance to real experiments. Holography, a precise one-to-one map from a weakly-coupled classical gravity in Anti de-Sitter space to a strongly-coupled conformal field theory living on its boundary that is embraced in string theory, provides one of the most promising possibilities, especially, through the application to condensed matter physics. This program has experienced various successes in condensed matter applications, an integrated and basic guiding principle has yet to be established. One of my goals is to understand the universal low energy physics of holographic backgrounds and to provide testable predictions for condensed matter physics. Inevitably, this will provide deeper understanding of holography and string theory. Some of my research topics are following with their own pages that you can visit.
VI. Selected Talks :
- “Skyrmions and Hall Transport,” Invited talk at the APS (American Physical Society) March Meeting, Los Angeles, California, March 5-9, 2018.
- “Skyrmions and Hall viscosity,” Invited talk at the 62nd Annual Conference on Magnetism and Magnetic Materials (MMM), Pittsburgh, Pennsylvania, November 6-10, 2017.
- “Entanglement Entropy with Current and Chemical potential,” May 2017 at the Great Lakes Strings Conference, University of Cincinnati, Cincinnati, USA.
- “Skyrmion charge, Ward identity and Hall transport,” Oct. 2015 at SPOCK regional string meeting, University of Cincinnati, Cincinnati, USA.
- “Hall Transport for Skyrmions,” May 2015 at Korea Institute for Advanced Study (KIAS), Seoul, Korea.
- “Parity breaking transports and Ward identities in 2+1 dimensions,” Mar. 2015 at the Great Lakes Strings Conference, University of Michigan, Ann Arbor, USA.
- “Lifshitz Hydrodynamics and its application to quantum critical region,” Mar. 2015 at University of California at Berkeley, Berkeley, USA.
- “Universal hydrodynamic description of quantum critical points with Lifshitz scaling,” July. 2013 at Kavli IPMU, University of Tokyo, Kashiwa, Japan.
- “Charged Dilatonic Black Holes and their thermodynamic and transport Properties,” July 2010 at ICTP, Trieste, Italy.
- “Transport properties of high Tc superconductor at very low temperature and AdS/CFT,” June 2011 at the Sixth Crete Regional Meeting in String Theory, Milos, Greece.
- “Charged Dilatonic Black Holes and their Transport Properties,” June 2010 at the XVIth European Workshop on String Theory, Madrid, Spain.
VII. Selected Publications :
For the full list of my publication, please visit the full publication list
- B. S. Kim, "Skyrmions and Hall viscosity," AIP Advances 8, 055601 (2018). [arXiv:1712.05032 [cond-mat.str-el]]
- B. S. Kim, "Entanglement Entropy with Background Gauge Fields," JHEP 1708, 041 (2017). arXiv:1706.07110 [hep-th].
- B. S. Kim, "Entanglement Entropy, Current, and Chemical Potential," arXiv:1705.01859 [hep-th].
- B. S. Kim, "Holographic Renormalization of Einstein-Maxwell-Dilaton Theories," JHEP 1611, 044 (2016). arXiv:1608.06252 [hep-th].
- B. S. Kim and A. Shapere, “Skyrmions and Hall Transport,” Phys. Rev. Lett. 117, 116805 (2016). [arXiv:1506.08199 [cond-mat.str-el]]
- C. Hoyos, B. S. Kim and Y. Oz, “Ward Identities for Hall Transport,” JHEP 1410, 054 (2014). [arXiv:1407.2616 [hep-th]]
- C. Hoyos, B. S. Kim and Y. Oz, “Lifshitz Field Theories at Non-Zero Temperature, Hydrodynamics and Gravity,” JHEP 1403, 029 (2014). [arXiv:1309.6794 [hep-th]]
- C. Hoyos, B. S. Kim and Y. Oz, “Lifshitz Hydrodynamics,” JHEP 1311, 145 (2013). [arXiv:1304.7481 [hep-th]]
- B. S. Kim, “Schroedinger Holography with and without Hyperscaling Violation,” JHEP 1206, 116 (2012). [arXiv:1202.6062 [hep-th]]
- B. S. Kim, E. Kiritsis and C. Panagopoulos, “Holographic quantum criticality and strange metal transport,” New J. Phys. 14:043045 (2012). [arXiv:1012.3464 [cond-mat.str-el]]
- C. Charmousis, B. Gouteraux, B. S. Kim, E. Kiritsis and R. Meyer, “Effective Holographic Theories for low-temperature condensed matter systems,” JHEP 1011, 151 (2010).[arXiv:1005.4690 [hep-th]]