QCLab - User contributions [en]

Harnessing Mesoscopic Mechanical Systems for New Quantum Technologies

2019-06-24T04:59:56Z

LeeMyeongwon:

[[file:Nobody.jpg|thumb|x300px|Prof. Hong, Sungkun (KAIST)]]
* Speaker: [[Hong, Sungkun|Prof. Hong, Sungkun (KAIST)]]
* Date: Wednesday May 15, 2019 05:00pm
* Place: Jungho Seminar Room

Quantum optomechanics is an emerging field in quantum science that aims to control quantum motions of mechanical objects using light-matter interactions. In recent years, the researchers started gaining quantum control over several mesoscopic mechanical systems. This advancement opens exciting possibilities for developing new quantum technologies and for testing quantum physics beyond the microscopic world. In this talk, I will describe two of my works on experimental quantum optomechanics.

I will present our progress in utilizing on-chip optomechanical devices as a new resource for quantum information processing. By combining pulsed optical controls and single photon detection, we created quantum states of a silicon micromechanical resonator at a single phonon level. Based on this method, we generated the remote entanglement between two mechanical modes, paving the way for mechanics-based optical quantum memories and networks.

I will also introduce a new optomechanical system that consists of an optically levitated nanoparticle and microfabricated photonic crystal cavities. This hybrid system will exhibit an exceptional combination of mechanical quality, flexibility, and controllability, allowing for a new level of quantum control over the particle’s motion. I will discuss the current status of the experiment and plans on further developing the system for novel quantum sensing applications.

<gallery mode="packed-hover">
Image:S-K_Hong_Seminar_3.jpg
Image:S-K_Hong_Seminar_2.jpg
</gallery>

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

File:S-K Hong Seminar 3.jpg

2019-06-24T04:28:56Z

LeeMyeongwon:

File:S-K Hong Seminar 2.jpg

2019-06-24T04:28:38Z

LeeMyeongwon:

Harnessing Mesoscopic Mechanical Systems for New Quantum Technologies

2019-06-24T04:28:16Z

LeeMyeongwon:

[[file:Nobody.jpg|thumb|x300px|Prof. Hong, Sungkun (KAIST)]]
* Speaker: [[Hong, Sungkun|Prof. Hong, Sungkun (KAIST)]]
* Date: Wednesday May 15, 2019 05:00pm
* Place: Jungho Seminar Room

Quantum optomechanics is an emerging field in quantum science that aims to control quantum motions of mechanical objects using light-matter interactions. In recent years, the researchers started gaining quantum control over several mesoscopic mechanical systems. This advancement opens exciting possibilities for developing new quantum technologies and for testing quantum physics beyond the microscopic world. In this talk, I will describe two of my works on experimental quantum optomechanics.

I will present our progress in utilizing on-chip optomechanical devices as a new resource for quantum information processing. By combining pulsed optical controls and single photon detection, we created quantum states of a silicon micromechanical resonator at a single phonon level. Based on this method, we generated the remote entanglement between two mechanical modes, paving the way for mechanics-based optical quantum memories and networks.

I will also introduce a new optomechanical system that consists of an optically levitated nanoparticle and microfabricated photonic crystal cavities. This hybrid system will exhibit an exceptional combination of mechanical quality, flexibility, and controllability, allowing for a new level of quantum control over the particle’s motion. I will discuss the current status of the experiment and plans on further developing the system for novel quantum sensing applications.

<gallery mode="packed-hover">
Image:S-K_Hong_Seminar_1.jpg
Image:S-K_Hong_Seminar_2.jpg
</gallery>

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

Precision metrology with Bose-Einstein Condensates

2019-05-22T09:36:44Z

LeeMyeongwon:

[[file:Jae Hoon Lee.jpg|thumb|x300px|Dr. Lee, Jae Hoon (KRISS)]]
* Speaker: [[Lee, Jae Hoon|Dr. Lee, Jae Hoon (KRISS)]]
* Date: Wednesday May 22, 2019 05:00pm
* Place: Jungho Seminar Room

Atomic systems, having the advantage of possessing universal properties, are widely used in
quantum sensors requiring absolute accuracy, such as atomic clocks. In particular, leveraging matter
wave interference in Bose-Einstein condensates (BECs) allow for “macroscopic” observation of
quantum effects that are typically attributed to the physical phenomena of single atoms. Atomic
physics experiments at KRISS are introduced which are geared towards precision metrology by
utilizing the amplification of quantum signatures with BECs. Furthermore, we explore ways to
generate, control, and measure quantum states in atomic and nanomechanical systems which can
lead to enhanced quantum sensing.

<gallery mode="packed-hover">
Image:J-H_Lee_Seminar_1.jpg
Image:seminarJ-H_Lee_Seminar_2.jpg
Image:seminarJ-H_Lee_Seminar_3.jpg
</gallery>

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

File:SeminarJ-H Lee Seminar 3.jpg

2019-05-22T09:36:19Z

LeeMyeongwon:

File:SeminarJ-H Lee Seminar 2.jpg

2019-05-22T09:35:58Z

LeeMyeongwon:

Precision metrology with Bose-Einstein Condensates

2019-05-22T09:34:31Z

LeeMyeongwon:

[[file:Jae Hoon Lee.jpg|thumb|x300px|Dr. Lee, Jae Hoon (KRISS)]]
* Speaker: [[Lee, Jae Hoon|Dr. Lee, Jae Hoon (KRISS)]]
* Date: Wednesday May 22, 2019 05:00pm
* Place: Jungho Seminar Room

Atomic systems, having the advantage of possessing universal properties, are widely used in
quantum sensors requiring absolute accuracy, such as atomic clocks. In particular, leveraging matter
wave interference in Bose-Einstein condensates (BECs) allow for “macroscopic” observation of
quantum effects that are typically attributed to the physical phenomena of single atoms. Atomic
physics experiments at KRISS are introduced which are geared towards precision metrology by
utilizing the amplification of quantum signatures with BECs. Furthermore, we explore ways to
generate, control, and measure quantum states in atomic and nanomechanical systems which can
lead to enhanced quantum sensing.

<gallery mode="packed-hover">
Image:J-H_Lee_Seminar_1.jpg
Image:J-H_Lee_Seminar_2.jpg
Image:J-H_Lee_Seminar_3.jpg
</gallery>

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

File:J-H Lee Seminar 1.jpg

2019-05-22T09:33:36Z

LeeMyeongwon: J-H_Lee_Seminar_1.jpg

== Summary ==
J-H_Lee_Seminar_1.jpg

Quantum Simulation Methods for Molecular Vibronic Spectra

2019-04-17T13:15:58Z

LeeMyeongwon:

[[file:Huh, Joonsuk.jpg|thumb|x300px|Prof. Huh, Joonsuk (Sungkyunkwan Univ.)]]

* Speaker: [[Huh, Joonsuk|Prof. Huh, Joonsuk (Sungkyunkwan Univ.)]]
* Date: Wednesday April 17, 2019 05:00pm
* Place: Jungho Seminar Room

Quantum computer is expected to attempt the quantum supremacy in near-term with potentially useful applications. Among the various quantum simulation problems, a quantum sampling problem with noninteracting bosonic particles, i.e. boson sampling, is very likely to demonstrate the quantum supremacy with relatively limited physical resources. In my talk, I will present a molecular problem (molecular vibronic spectra), which can be interpreted as a Gaussian boson sampling problem. Additionally, a quantum circuit based algorithm for the same molecular problem will be presented.

<gallery mode="packed-hover">
Image:J-S_Huh_Seminar_1.jpg
Image:J-S_Huh_Seminar_2.jpg
Image:J-S_Huh_Seminar_3.png
</gallery>

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

File:J-S Huh Seminar 3.png

2019-04-17T13:15:46Z

LeeMyeongwon:

File:J-S Huh Seminar 3.jpg

2019-04-17T13:13:19Z

LeeMyeongwon: LeeMyeongwon uploaded a new version of File:J-S Huh Seminar 3.jpg

File:J-S Huh Seminar 3.jpg

2019-04-17T13:12:02Z

LeeMyeongwon:

File:J-S Huh Seminar 2.jpg

2019-04-17T13:11:48Z

LeeMyeongwon:

File:J-S Huh Seminar 1.jpg

2019-04-17T13:11:33Z

LeeMyeongwon:

Quantum Simulation Methods for Molecular Vibronic Spectra

2019-04-17T13:08:19Z

LeeMyeongwon:

[[file:Huh, Joonsuk.jpg|thumb|x300px|Prof. Huh, Joonsuk (Sungkyunkwan Univ.)]]

* Speaker: [[Huh, Joonsuk|Prof. Huh, Joonsuk (Sungkyunkwan Univ.)]]
* Date: Wednesday April 17, 2019 05:00pm
* Place: Jungho Seminar Room

Quantum computer is expected to attempt the quantum supremacy in near-term with potentially useful applications. Among the various quantum simulation problems, a quantum sampling problem with noninteracting bosonic particles, i.e. boson sampling, is very likely to demonstrate the quantum supremacy with relatively limited physical resources. In my talk, I will present a molecular problem (molecular vibronic spectra), which can be interpreted as a Gaussian boson sampling problem. Additionally, a quantum circuit based algorithm for the same molecular problem will be presented.

<gallery mode="packed-hover">
Image:J-S_Huh_Seminar_1.jpg
Image:J-S_Huh_Seminar_2.jpg
Image:J-S_Huh_Seminar_3.jpg
</gallery>

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

ON QUANTUM DIALOGUE

2019-03-27T11:35:42Z

LeeMyeongwon:

[[file:Prof_An.png|thumb|x300px|Prof. Nguyen Ba An (Thang Long University, Vietnam)]]
* Speaker: [[Nguyen Ba An|Prof. Nguyen Ba An (Thang Long University, Vietnam)]]
* Date: Wednesday March 27, 2019 05:00pm
* Place: Jungho Seminar Room

Secure communication is a legitimate demand of the mankind. In order for one party (Alice) to send a confidential message to another party (Bob), the two have to share beforehand a secret key which must be used only once to encode/decode the message. Such a “one-time” private-key system for communication is absolutely secure but inconvenient in practice. Of current use is the public-key system which is very convenient practically, but its (unproven) security will be broken if quantum computers come into birth. To guarantee unconditional security even in the presence of quantum computers, quantum key distribution (QKD) needs to be deployed prior to an actual communication. That is, resorting to the laws of Nature, Alice and Bob are able to remotely establish secret keys under the nose of any eavesdroppers. However, what should be done in emergent circumstances when Alice and Bob wish to directly exchange their information but do not have enough time to implement a QKD protocol? In other words, can they still securely "talk" with each other without a prior key distribution? We show that this turns out to be possible by means of the so-called "quantum dialogue", which rationally exploits the quantum entanglement resources, quantum operations and quantum measurements [1,2]. Somewhat more surprisingly, even quantum nonselective measurements (i.e., measurements without reading the outcome) make sense to the quantum dialogue [3], an unbelievably counterintuitive fact in our everyday life!

[1] N. B. An, Phys. Lett. A 328, 6 (2004): Quantum dialogue

[2] N. B. An, J. Kor. Phys. Soc. 47, 562 (2005): Secure dialogue without a prior key distribution

[3] N. B. An, Adv. Nat. Sci.: Nanosci. Nanotech. 9, 025001 (2018): Quantum dialogue by nonselective measurements

<gallery mode="packed-hover">
Image:N-B_An_Seminar_1.jpg
Image:N-B_An_Seminar_2.jpg
Image:N-B_An_Seminar_5.jpg
</gallery>

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

File:N-B An Seminar 5.jpg

2019-03-27T11:35:30Z

LeeMyeongwon:

File:N-B An Seminar 3.jpg

2019-03-27T11:33:23Z

LeeMyeongwon:

File:N-B An Seminar 2.jpg

2019-03-27T11:33:11Z

LeeMyeongwon:

File:N-B An Seminar 1.jpg

2019-03-27T11:32:58Z

LeeMyeongwon:

ON QUANTUM DIALOGUE

2019-03-27T11:32:33Z

LeeMyeongwon:

[[file:Prof_An.png|thumb|x300px|Prof. Nguyen Ba An (Thang Long University, Vietnam)]]
* Speaker: [[Nguyen Ba An|Prof. Nguyen Ba An (Thang Long University, Vietnam)]]
* Date: Wednesday March 27, 2019 05:00pm
* Place: Jungho Seminar Room

Secure communication is a legitimate demand of the mankind. In order for one party (Alice) to send a confidential message to another party (Bob), the two have to share beforehand a secret key which must be used only once to encode/decode the message. Such a “one-time” private-key system for communication is absolutely secure but inconvenient in practice. Of current use is the public-key system which is very convenient practically, but its (unproven) security will be broken if quantum computers come into birth. To guarantee unconditional security even in the presence of quantum computers, quantum key distribution (QKD) needs to be deployed prior to an actual communication. That is, resorting to the laws of Nature, Alice and Bob are able to remotely establish secret keys under the nose of any eavesdroppers. However, what should be done in emergent circumstances when Alice and Bob wish to directly exchange their information but do not have enough time to implement a QKD protocol? In other words, can they still securely "talk" with each other without a prior key distribution? We show that this turns out to be possible by means of the so-called "quantum dialogue", which rationally exploits the quantum entanglement resources, quantum operations and quantum measurements [1,2]. Somewhat more surprisingly, even quantum nonselective measurements (i.e., measurements without reading the outcome) make sense to the quantum dialogue [3], an unbelievably counterintuitive fact in our everyday life!

[1] N. B. An, Phys. Lett. A 328, 6 (2004): Quantum dialogue

[2] N. B. An, J. Kor. Phys. Soc. 47, 562 (2005): Secure dialogue without a prior key distribution

[3] N. B. An, Adv. Nat. Sci.: Nanosci. Nanotech. 9, 025001 (2018): Quantum dialogue by nonselective measurements

<gallery mode="packed-hover">
Image:N-B_An_Seminar_1.jpg
Image:N-B_An_Seminar_2.jpg
Image:N-B_An_Seminar_3.jpg
</gallery>

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

Chung, Jae-Ho

2019-03-19T02:33:44Z

LeeMyeongwon:

[[file:Jae-Ho Chung.jpg|thumb|x300px|Prof. Jae-Ho Chung (Korea Univ.)]]

<blockquote>
'''Professor in Department of Physics at Korea University'''
</blockquote>

Jae-Ho Chung is a condensed matter physicist specializing in magnetic materials. He received is B.S. degree (1992) from Seoul National University and Ph.D. (2003) from the University of Pennsylvania. Before coming to Korea University He was a postdoc at the University of Maryland and the NIST Center for Neutron Research.

==Research Interests==
Spin order and disorder in geometrically frustrated antiferromagnets, competition between lattice and spin degrees of freedom, magnetic order and dynamics of magneto-electric multiferroics, lattice dynamics and electron-lattice interactions, exchange couplings in magnetic semiconductors.

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

Chung, Jae-Ho

2019-03-19T02:33:30Z

LeeMyeongwon:

[[file:Jae-Ho Chung.jpg|thumb|x300px|Prof. Jae-Ho Chung (Korea Univ)]]

<blockquote>
'''Professor in Department of Physics at korea University'''
</blockquote>

Jae-Ho Chung is a condensed matter physicist specializing in magnetic materials. He received is B.S. degree (1992) from Seoul National University and Ph.D. (2003) from the University of Pennsylvania. Before coming to Korea University He was a postdoc at the University of Maryland and the NIST Center for Neutron Research.

==Research Interests==
Spin order and disorder in geometrically frustrated antiferromagnets, competition between lattice and spin degrees of freedom, magnetic order and dynamics of magneto-electric multiferroics, lattice dynamics and electron-lattice interactions, exchange couplings in magnetic semiconductors.

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

Harnessing Mesoscopic Mechanical Systems for New Quantum Technologies

2019-03-13T09:24:50Z

LeeMyeongwon:

[[file:Nobody.jpg|thumb|x300px|Prof. Hong, Sungkun (KAIST)]]
* Speaker: [[Hong, Sungkun|Prof. Hong, Sungkun (KAIST)]]
* Date: Wednesday May 15, 2019 05:00pm
* Place: Jungho Seminar Room

Quantum optomechanics is an emerging field in quantum science that aims to control quantum motions of mechanical objects using light-matter interactions. In recent years, the researchers started gaining quantum control over several mesoscopic mechanical systems. This advancement opens exciting possibilities for developing new quantum technologies and for testing quantum physics beyond the microscopic world. In this talk, I will describe two of my works on experimental quantum optomechanics.

I will present our progress in utilizing on-chip optomechanical devices as a new resource for quantum information processing. By combining pulsed optical controls and single photon detection, we created quantum states of a silicon micromechanical resonator at a single phonon level. Based on this method, we generated the remote entanglement between two mechanical modes, paving the way for mechanics-based optical quantum memories and networks.

I will also introduce a new optomechanical system that consists of an optically levitated nanoparticle and microfabricated photonic crystal cavities. This hybrid system will exhibit an exceptional combination of mechanical quality, flexibility, and controllability, allowing for a new level of quantum control over the particle’s motion. I will discuss the current status of the experiment and plans on further developing the system for novel quantum sensing applications.

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

Quantum meets Mechanics: Mechanical Systems as New Resources for Quantum Technologies

2019-02-28T12:03:06Z

LeeMyeongwon:

[[file:Hong, Sungkun.jpg|thumb|x300px|Prof. Hong, Sungkun (KAIST)]]
* Speaker: [[Hong, Sungkun|Prof. Hong, Sungkun (KAIST)]]
* Date: Wednesday May 15, 2019 05:00pm
* Place: Jungho Seminar Room

Studying quantum behaviors of mesoscopic mechanical systems is an emerging field in quantum science. The main experimental approach is optomechanics, where photons (or electromagnetic radiations) are used to measure and manipulate the motional states of mechanical structures like micromechanical oscillators. Optomechanics, together with advancements in micro- and nanofabrication, has allowed us to observe and control mechanical resonators at a quantum level. This opens new exciting possibilities for quantum science and technology as well as for studying quantum physics in hitherto untested macroscopic scales. In this talk, I will describe two of my major researches on experimental quantum optomechanics.
I will first report on our progress in utilizing on-chip optomechanical devices as a new resource for quantum information. Combining pulsed optical controls and single photon detection, we demonstrated a method that creates quantum states of a silicon micromechanical resonator at a single phonon level. Using this scheme, we generated the remote entanglement between two mechanical modes, paving the way for mechanics-based optical quantum memory and network.
Next, I will introduce a novel, hybrid optomechanical system consisting of optically levitated nanoparticles and micro-fabricated photonic crystal cavity. The system combines excellent mechanical quality and flexibility stemming from optical levitation and an efficient optical interface based on nanophotonic cavities. It thus opens completely new possibilities for mechanics-based quantum sensing and genuine quantum experiments on the macroscopic motion of the particle. I will discuss the current status of the experiment and future plans of the work that include the development of novel quantum sensors and the matter-wave interferometry in new mass scales.

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

Hong, Sungkun

2019-02-28T01:52:39Z

LeeMyeongwon:

[[file:Hong, Sungkun.jpg|thumb|x300px|Prof. Hong, Sungkun (KAIST)]]
Professor at KAIST

==Education==
* Ph.D. Applied Physics, Harvard University, 2013
* B.S. Mechanical and Aerospace Engineering, Seoul National University, 2003

==Professional Experiences==
* Assistant Professor, KAIST, March 2109 - Present
* Postdoctoral Researcher, University of Vienna, Jan 2013 - Feb 2019

==Contributions==
* [[Quantum meets Mechanics: Mechanical Systems as New Resources for Quantum Technologies]]

[[Category:Speakers]]
[[Category:Condensed Matter Speakers]]

File:Huh, Joonsuk.jpg

2019-02-26T07:47:10Z

LeeMyeongwon:

Quantum Simulation Methods for Molecular Vibronic Spectra

2019-02-26T07:46:59Z

LeeMyeongwon:

[[file:Huh, Joonsuk.jpg|thumb|x300px|Prof. Huh, Joonsuk (Sungkyunkwan Univ.)]]

* Speaker: [[Huh, Joonsuk|Prof. Huh, Joonsuk (Sungkyunkwan Univ.)]]
* Date: Wednesday April 17, 2019 05:00pm
* Place: Jungho Seminar Room

Quantum computer is expected to attempt the quantum supremacy in near-term with potentially useful applications. Among the various quantum simulation problems, a quantum sampling problem with noninteracting bosonic particles, i.e. boson sampling, is very likely to demonstrate the quantum supremacy with relatively limited physical resources. In my talk, I will present a molecular problem (molecular vibronic spectra), which can be interpreted as a Gaussian boson sampling problem. Additionally, a quantum circuit based algorithm for the same molecular problem will be presented.

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

File:S-Y Jung Seminar 3.jpg

2018-12-20T02:07:18Z

LeeMyeongwon:

File:S-Y Jung Seminar 2.jpg

2018-12-20T02:07:02Z

LeeMyeongwon:

File:S-Y Jung Seminar 1.jpg

2018-12-20T02:06:44Z

LeeMyeongwon:

Probing Atomic Defect States of Monolayer Semiconducting Transition Metal Dichalcogenide Film

2018-12-20T02:06:27Z

LeeMyeongwon:

[[file:S-Y_Jung.jpg|thumb|x300px|Dr. Jung, Suyong (KRISS)]]
* Speaker: [[Jung, Suyong|Dr. Jung, Suyong (KRISS)]]
* Date: Wednesday December 19, 2018 05:00pm
* Place: Jungho Seminar Room

Assessing atomic defect states and their ramifications in the electronic properties of two-dimensional (2D) van der Waals (vdW) semiconducting transition metal dichalcogenides (TMDs) is the first and primary task to expedite multi-disciplinary inquisitions for promoting next-generation electrical and optical device applications with these exciting low-dimensional quantum materials. Here, with an electron tunneling and optical spectroscopy measurements combined with a density functional theory, we spectroscopically locate mid-gap states originated from single chalcogen atom vacancies in the four representative semiconducting monolayer TMD (mTMD) films; WS2, MoS2, WSe2, and MoSe2, with an unprecedentedly high fidelity, and carefully analyze similarities and dissimilarities as to the physical formation of atomic defects and their implications in the respective mTMD semiconducting properties. In addition, we can accurately address both the quasiparticle and optical energy gaps of the intrinsic mTMD films, and find out that Coulombic many body interactions significantly enlarge the quasiparticle energy gaps, and excitonic binding energies which are determined to be 0.83 eV (mWS2), 0.76 eV (mMoS2), 0.82 eV (mWSe2), and 0.82 eV (mMoSe2) when the single-atomic thick semiconducting layers are encapsulated with non-interacting high quality hexagonal boron nitride layers.

<gallery mode="packed-hover">
Image:S-Y_Jung_Seminar_1.jpg
Image:S-Y_Jung_Seminar_2.jpg
Image:S-Y_Jung_Seminar_3.jpg
</gallery>

{{Media/Button|J-SY2018d.pdf|Talk slides}}

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

File:Y-S Oh Seminar 3.jpg

2018-12-12T11:23:57Z

LeeMyeongwon:

File:Y-S Oh Seminar 2.jpg

2018-12-12T11:23:46Z

LeeMyeongwon:

File:Y-S Oh Seminar 1.jpg

2018-12-12T11:23:33Z

LeeMyeongwon:

Large Lattice Constant and Large Band Gap Cubic Perovskite: BaZrO3 Single Crystal

2018-12-12T11:21:19Z

LeeMyeongwon:

[[file:Y-S_Oh.jpg|thumb|x300px|Prof. Yoon Seok Oh (UNIST)]]
* Speaker: [[Oh, Yoon Seok|Prof. Oh, Yoon Seok (UNIST)]]
* Date: Wednesday December 12, 2018 05:00pm
* Place: Jungho Seminar Room

Named after Russian mineralogist L. Perovski, Perovskite is material which has the chemical formula ABX3 (where A and B are cations, and X is an anion) and a crystal structure with the anion X in the face centers. The Perovskite compounds exhibit a variety of exotic physical phenomena, such as high-Tc superconductivity as well as quantum criticality, heavy fermion, multiferroics, morphotropic phase boundary. In terms of new functional material design, the Perovskite has high tunability. It’s possible that selective chemical substitution of atomic sites induces various orthorhombic distortions as well as cubic. In addition, it can also form layered structure, so called Ruddlesden-Popper structure, composed of one or multiple ABX3 two-dimensional perovskite slabs and AX rock salt interleave layers. Recently, in the hybrid inorganic-organic framework with the Perovskite architecture, highly efficient solar cell application was demonstrated. Because of its variety and the intriguing physics, there has been lots of attention to Perovskite compounds during the last 30 years. Recently, we successfully grow stoichiometric cubic BaZrO3 single crystal, whose energy band gap is 5.0 eV, with size of 5 mm × 5 mm × 5 mm. Using X-ray diffraction, atomic force microscope, ultraviolet-visible-near-infrared transmission spectra, transmission electron microscope, comprehensive structure and electronic properties have been studied.

<gallery mode="packed-hover">
Image:Y-S_Oh_Seminar_1.jpg
Image:Y-S_Oh_Seminar_2.jpg
Image:Y-S_Oh_Seminar_3.jpg
</gallery>

{{Media/Button|O-YS2018d.pdf|Talk slides}}

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

Jung, Suyong

2018-12-12T05:07:29Z

LeeMyeongwon: Created page with "Dr. Jung, Suyong (KRISS) Reseach Fellow at KRISS ==Education== * Ph.D. Department of Physics, The University of Texas, Austin, 2007 * B.S...."

[[file:S-Y_Jung.jpg|thumb|x300px|Dr. Jung, Suyong (KRISS)]]

Reseach Fellow at KRISS

==Education==
* Ph.D. Department of Physics, The University of Texas, Austin, 2007
* B.S. Department of Physics, Seoul National University, 2001

==Professional Experiences==
* Principal Research Scientist, Quantum Technology Institute, KRISS, 2016 - Present
* Senior Research Scientist, Center for Quantum Measurement Science, KRISS, 2012 - 2015
* Postdoctoral Research Associate, Center for Nanoscience and Technology (CNST), 2007 - 2012

==Contributions==
* [[Probing Atomic Defect States of Monolayer Semiconducting Transition Metal Dichalcogenide Film]]

[[Category:Speakers]]
[[Category:Condensed Matter Speakers]]

Probing Atomic Defect States of Monolayer Semiconducting Transition Metal Dichalcogenide Film

2018-12-12T05:00:39Z

LeeMyeongwon:

[[file:S-Y_Jung.jpg|thumb|x300px|Dr. Jung, Suyong (KRISS)]]
* Speaker: [[Jung, Suyong|Dr. Jung, Suyong (KRISS)]]
* Date: Wednesday December 19, 2018 05:00pm
* Place: Jungho Seminar Room

Assessing atomic defect states and their ramifications in the electronic properties of two-dimensional (2D) van der Waals (vdW) semiconducting transition metal dichalcogenides (TMDs) is the first and primary task to expedite multi-disciplinary inquisitions for promoting next-generation electrical and optical device applications with these exciting low-dimensional quantum materials. Here, with an electron tunneling and optical spectroscopy measurements combined with a density functional theory, we spectroscopically locate mid-gap states originated from single chalcogen atom vacancies in the four representative semiconducting monolayer TMD (mTMD) films; WS2, MoS2, WSe2, and MoSe2, with an unprecedentedly high fidelity, and carefully analyze similarities and dissimilarities as to the physical formation of atomic defects and their implications in the respective mTMD semiconducting properties. In addition, we can accurately address both the quasiparticle and optical energy gaps of the intrinsic mTMD films, and find out that Coulombic many body interactions significantly enlarge the quasiparticle energy gaps, and excitonic binding energies which are determined to be 0.83 eV (mWS2), 0.76 eV (mMoS2), 0.82 eV (mWSe2), and 0.82 eV (mMoSe2) when the single-atomic thick semiconducting layers are encapsulated with non-interacting high quality hexagonal boron nitride layers.

{{Media/Button|J-SY2018d.pdf|Talk slides}}

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

File:S-Y Jung.jpg

2018-12-12T05:00:09Z

LeeMyeongwon:

Probing Atomic Defect States of Monolayer Semiconducting Transition Metal Dichalcogenide Film

2018-12-12T04:57:44Z

LeeMyeongwon: Created page with "Dr. Jung, Suyong (KRISS) * Speaker: Dr. Jung, Suyong (KRISS) * Date: Wednesday December 19, 2018 05:00pm * Place: Jungho Se..."

[[file:S-Y_Jung.jpg|thumb|x300px|Dr. Jung, Suyong (KRISS)]]
* Speaker: [[Jung, Suyong|Dr. Jung, Suyong (KRISS)]]
* Date: Wednesday December 19, 2018 05:00pm
* Place: Jungho Seminar Room

Assessing atomic defect states and their ramifications in the electronic properties of two-dimensional (2D) van der Waals (vdW) semiconducting transition metal dichalcogenides (TMDs) is the first and primary task to expedite multi-disciplinary inquisitions for promoting next-generation electrical and optical device applications with these exciting low-dimensional quantum materials. Here, with an electron tunneling and optical spectroscopy measurements combined with a density functional theory, we spectroscopically locate mid-gap states originated from single chalcogen atom vacancies in the four representative semiconducting monolayer TMD (mTMD) films; WS2, MoS2, WSe2, and MoSe2, with an unprecedentedly high fidelity, and carefully analyze similarities and dissimilarities as to the physical formation of atomic defects and their implications in the respective mTMD semiconducting properties. In addition, we can accurately address both the quasiparticle and optical energy gaps of the intrinsic mTMD films, and find out that Coulombic many body interactions significantly enlarge the quasiparticle energy gaps, and excitonic binding energies which are determined to be 0.83 eV (mWS2), 0.76 eV (mMoS2), 0.82 eV (mWSe2), and 0.82 eV (mMoSe2) when the single-atomic thick semiconducting layers are encapsulated with non-interacting high quality hexagonal boron nitride layers.

{{Media/Button|J-SY2018d.pdf|Talk slides}}

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

File:O-YS2018d.pdf

2018-12-06T11:58:07Z

LeeMyeongwon:

Large Lattice Constant and Large Band Gap Cubic Perovskite: BaZrO3 Single Crystal

2018-12-06T11:57:48Z

LeeMyeongwon: Created page with "Prof. Yoon Seok Oh (UNIST) * Speaker: Prof. Oh, Yoon Seok (UNIST) * Date: Wednesday December 12, 2018 04:30pm * Place: Jungh..."

[[file:Y-S_Oh.jpg|thumb|x300px|Prof. Yoon Seok Oh (UNIST)]]
* Speaker: [[Oh, Yoon Seok|Prof. Oh, Yoon Seok (UNIST)]]
* Date: Wednesday December 12, 2018 04:30pm
* Place: Jungho Seminar Room

Named after Russian mineralogist L. Perovski, Perovskite is material which has the chemical formula ABX3 (where A and B are cations, and X is an anion) and a crystal structure with the anion X in the face centers. The Perovskite compounds exhibit a variety of exotic physical phenomena, such as high-Tc superconductivity as well as quantum criticality, heavy fermion, multiferroics, morphotropic phase boundary. In terms of new functional material design, the Perovskite has high tunability. It’s possible that selective chemical substitution of atomic sites induces various orthorhombic distortions as well as cubic. In addition, it can also form layered structure, so called Ruddlesden-Popper structure, composed of one or multiple ABX3 two-dimensional perovskite slabs and AX rock salt interleave layers. Recently, in the hybrid inorganic-organic framework with the Perovskite architecture, highly efficient solar cell application was demonstrated. Because of its variety and the intriguing physics, there has been lots of attention to Perovskite compounds during the last 30 years. Recently, we successfully grow stoichiometric cubic BaZrO3 single crystal, whose energy band gap is 5.0 eV, with size of 5 mm × 5 mm × 5 mm. Using X-ray diffraction, atomic force microscope, ultraviolet-visible-near-infrared transmission spectra, transmission electron microscope, comprehensive structure and electronic properties have been studied.

{{Media/Button|O-YS2018d.pdf|Talk slides}}

[[Category:Seminars]]
[[Category:Condensed Matter Seminars]]

File:H-S Choi Seminar 3.jpg

2018-11-28T12:31:34Z

LeeMyeongwon:

File:H-S Choi Seminar 2.jpg

2018-11-28T12:31:16Z

LeeMyeongwon:

File:H-S Choi Seminar 1.jpg

2018-11-28T12:30:51Z

LeeMyeongwon:

Probing Topological Superfluidity with Nano/Micromechanics

2018-11-28T12:29:34Z

LeeMyeongwon:

[[file:H-S_Choi_Reupload.png|frame|Prof. Hyoungsoon Choi (KAIST)]]

* Speaker: Prof. [[Choi, Hyoungsoon|Hyoungsoon Choi]] (KAIST)
* Date: Wednesday, November 7, 2018, at 17:00
* Place: Jungho Seminar

Topological matters have drawn the focus of condensed matter physicists for the better part of past decade. Topological superconductors have been of particular interest due to their potential to host the so-called Majorana fermions, an elusive particle whose anti-particle is the particle itself. Most of the efforts have revolved around synthesizing a new breed of topological superconductors by combining topological insulators, superconductors and magnetic materials. A more naturally produced topological superfluid, 3He, on the other hand, has been considered to be more difficult to probe due to its charge neutral nature. Nano/micromechanical systems provide a new path for studying topological superfluidity in this charge neutral system and we have developed NEMS/MEMS devices for this purpose. In this talk, I will discuss how NEMS/MEMS devices can be used in topological superfluid research and report our progress.

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[[Category:Condensed Matter Seminars]]
[[Category:Seminars]]

File:K-B Chung Seminar 3.jpg

2018-11-28T12:28:58Z

LeeMyeongwon:

File:K-B Chung Seminar 2.jpg

2018-11-28T12:28:31Z

LeeMyeongwon:

File:K-B Chung Seminar 1.jpg

2018-11-28T12:28:02Z

LeeMyeongwon: