Salam’s Dream and Dynamic Changes
in Chinese Condensed Matter Physics
-A Personal Perspective
Memorial Meeting for Abdus Salam’s 90 Birthday
25-28 January, 2016, Singapore
Lu Yu
Institute of Physics,
Chinese Academy of Sciences
“Scientific thought is the common
heritage of all mankind.”
-Abdus Salam
In recent times, in this adventure of discovery on the
frontier, the South has not been able to play a
commensurate role...principally because of lack of
opportunity. This, however, is not a situation which
young men and women from the Third World will accept.
They enviously, and deservedly, long to participate in
this exciting adventure of scientific creation on equal
terms.
-Abdus Salam, TWAS Inauguration Meeting, 1985
 Professor Abdus Salam was the ‘wise man’,
mentor in my career. 1986-2002, at ICTP,
1986-96, directly under his supervision.
 Witness how he devoted his wisdom, energy,
heart and soul to materialize the dream for
the developing world.
 Witness how his dream is coming true, at
least partially, in some parts of the South,
including China, although the path is not
straightforward, full of challenges, difficulties.
Half-century ago modern CM physics
was almost non-existent in China
• Before 1949, the basis for science was very weak
because of war……
• After 1949, “everything needs a boost”, a few welltrained physicists returned to China, like Kun Huang,
Xide Xie, Kaijia Chen, Yinyuan Li, but because of the
cold war, total isolation from the West
Since beginning of 21 century Chinese
CM physics entered the fast track:
•A number of outstanding young physicists with cutting-edge output emerged in the World arena
How did the quantal transition occur?
Humble beginnings
Interruption by ‘cultural revolution’
Opening-up and recovery
17 years at ICTP
Current developments and some
remarks
Way out: ”learning from Soviet Union”,
reform of education system, sending
students for study, in less than 10 years,
about 8000 young people got Diploma or
“candidates” (Ph.D.) degrees
I was fortunate to be one of them:
1956-1961 Kharkov State University,
Diploma Thesis Supervisor: M.I. Kaganov
Kharkov is the city where L.D. Landau
created his school in physics. After his
move to Moscow, I.M. Lifshitz took over
the leadership
L. Landau
I.M. Lifshitz
However, the good fortune did not last
too long: China and SU broke up, no way
to continue for Ph.D. More than that:
No traveling for 17 years. To meet former
supervisor only after 26 years!
A New Start
1961 joined Institute of Physics, created in 1928
Rather poor material conditions, but encouraging
environment, appointed as group leader at 24
Self- and mutual education to make up the lack
of supervision.
Intensive study and inspiring
discussions. Group leader: Chunxian Chen who
had chance to work for about two years as a
diploma student in Prof. N. N. Bogoliubov’s group
Fortunate outcome: 4 out of 5 key members later were
elected to the membership of the Chinese Academy of
Sciences
Shigang
CHEN
Yuping
HUO
Bailin
HAO
Lu
YU
Cooper pairing of time-reversal states;
k↑和－k↓
Anderson theorem: no dramatic effects of
non-magnetic impurities
Perturbative approach to treat time-reversal
symmetry breaking - reduction of energy
gap and transition temperature (Abrikosov,
Gor’kov)
Is it possible to form a bound state like in
semiconductors?
As a big exercise, bound state in
superconductors with paramagnetic
impurities:
A self-consistent solution of the generalized
Bogoliubov transformation
( Bogoliubov-de Gennes Eq)
Also calculated additional EM absorption
and tunneling current
1968 H. Shiba， 1969 A.I. Rusinov, made
similar predictions
1981 Observed in tunneling, Prof. Buckel
1997 Direct observation by STM, A. Yazdani
1994 Los Alamos，impurity effects on
D-wave superconductors- A. Balatsky
A.Yazdani et al., Science 275,1767(1997)
S.H.Ji et al, PRL 100,226801 (2008)
p-wave superconductivity and Majorana fermions
=
+ ( +
)
A fermionic particle whose antiparticle is itself
A p-wave superconductor is a natural host of MF
Li Lv
Superconducting …
Fu & Kane, (PRL 2008):
Pairing of helical electrons via proximity effect at
s-wave superconductor-TI interface
resembling spinless px+ipy-wave superconductivity
Li Lv
Zero biased peak
Humble beginnings
Interruption by ‘cultural revolution’
Opening-up and recovery
17 years at ICTP
Current developments and some
remarks
1969－1971 “May 7th” school
1971 experimental work on
superconductivity
1972 “anatomize” “NOVA” minicomputer
Second visit of C.N. Yang to China,
meeting with Chou En-Lai, article in
“Guangming Daily” on importance of
fundamental research
1972 my colleague Bailin Hao attended
the Annual Meeting of Canad. Assoc.of
Phys. Heard talk by M.E. Fisher on
Ken Wilson’s work
We went to the library: Journals were
not displayed, but received:
Surprisingly finding the enormous
progress on phase transition and critical
phenomena
Strong feeling of lagging behind
Making up with anxiety: to study and
share all important papers one-by-one
During the process of learning:
Calculation of the critical exponents
by Yu Lu and Hao Bailin
Skeleton Graph Expansion for
Critical Exponents of Continuous
Phase Transitions
YU Lu
HAO Bailin
Institute of Physics, Chinese Academy of Sciences
No abstract, even no title in English
Skeleton graph expansion
E. Brezin et al. , Phys. Lett.
44A, 227 (1973)
Two pages of brief report,
no derivations
Another important event during ‘cultural
revolution’- visit of a delegation from American
Physical Society in 1975, as a reciprocal visit of
Chinese Solid State Physics delegation to the US
in March-April, 1975.
“ The Solid State Physics delegation wished to
make an in-depth study of major areas of solid
state physics research and teaching in the People’s
Republic of China.” –-from the exchange letter in
arranging the visit.
One-month visit: 4 Sept.- 2 Oct., 1975
10 eminent Solid
State Physicists
Charles Slichter
Nicolaas Bloembergen Leroy Chang
Ted Geballe
Conyers Herring
Ivar Giaever
Bob Schrieffer
John Bardeen
John Gilman
Bob Silsbee
Contents
1 The roots of science in China
today
2 Visits to research institutes
and universities
3 Research in solid state physics
4 The new approach to science
education
5 Communicating the fruits of
research
6 Reflections on our visits
National Academy of Sciences
Press, Washington, 1976,
219 pages
Appendices
1975年与 Bob Schrieffer 在物理所合影
Comments on our work:
“Some theorists attached to the magnetism
group of the Institute of Physics described to us
some rather sophisticated and innovative work on
critical exponents near continuous-phase transition
points. This study used renormalization-group
theory and diagrammatic analysis, methods similar
to those used in the most advanced contemporary
work in the West and in the Soviet Union … These
studies were the most conspicuous exception we
found to the general pattern of the Chinese solid
state theorists’ preoccupation with classical or
semi-classical phenomenology.”
Humble beginnings
Interruption by ‘cultural revolution’
Opening-up and recovery
17 years at ICTP
Current developments and some
remarks
To attend the 17th Solvay Conference at Brussels,
in 1978:
“Order and Fluctuations in Equilibrium and NonEquilibrium Statistical Mechanics”,
first scientific exchange after 17 years, to meet
P.W. Anderson, L. Kadanoff, M.Fisher, and
many others.
1979-1980 to visit B. Halperin ‘s
group, to regain the feeling of
front-line research.
 Bert jokingly called me “Senior
postdoc”
Visiting Bob Schrieffer at UC Santa Barbara, 1981
Humble beginnings
Interruption by ‘cultural revolution’
Opening-up and recovery
17 years at ICTP
Current developments and some
remarks
Prof. Abdus Salam
Prof. Stig Lundqvist
1983 Lundqvist’s visit to China,
invitation to ICTP, Chalmers U. and
NORDITA.
Second visit to ICTP as an associate
Establishment of new staff position,
first directly coming from developing
countries
Suggestion by Stig Lundqvist to take
up this position
Approval by Professor Abdus Salam
Professor Salam’s letter dated
25 October, 1985
From Professor Salam’s letter:
2. We would like the Condensed Matter activities
in developing countries to be enhanced through
your presence here at the Centre. This will
mean:
(a) … one of the tasks is the responsibility
for building up in developing countries the
solid state communities where they do not
exist…
(b) Since Condensed Matter Physics is more
concerned with development issues…… we
would appreciate your keeping this activity
very much in mind…
4. Finally, if I may humble say this, the continuation of the position… depends … on the success which is achieved in helping with the objectives in respect of enhancing studies and
use of Condensed Matter Physics in developing
countries set above.
We all look forward to a second revolution in
the Condensed Matter Activity in developing
countries with your appointment and through
your influence
Profound respect and anxiety, at the same time
ICTP-SISSA have played a crucial
role in helping China to train young
scientists and to integrate them to
the World scientific community
Most scientists in physics, mathematics and some
applied scientists went out to the international
arena through ICTP-SISSA
Many senior scientists benefited a lot, like
Hao Bailin, Su Zhaobin, Pu Fucho, Tao Ruibao,
Zhu Banfeng, and many others
A number of current leading figures have grownup from ICTP-SISSA training
5342 visitors, 193 associates, 41 TRIL fellows
Under Professor Salam’s supervision the duties at ICTP
were performed well, and Yu Lu was awarded the
American Institute of Physics Tate Medal for
International Leadership in Physics in recognition of four
decades of landmark contributions in bringing together
the world’s condensed matter
physics community, the support
of young scientists, the creation
of important international
conferences, and international
statesmanship in theoretical
physics.
Professor Salam was awarded
the same medal in 1978
Humble beginnings
Interruption by ‘cultural revolution’
Opening-up and recovery
17 years at ICTP
Current developments and some
remarks
Many years of concerted efforts
have produced some visible results
One example:
Iron-based superconductors
Many groups in China have made
important contributions
Dirac & Weyl Fermion
Dirac equation (1928) 4x4
Prediction of positron
Massive Dirac Fermion
Weyl equation (1929) 2x2
Prediction of Weyl fermion
H. Weyl, “Electron and gravitation,” Z. Phys. 56, 330 (1929)
Massless Dirac Fermion:
two Weyl Fermions with
opposite topological
charges “kiss”.
H. Ding
Rescue from condensed matter: quasiparticle
• Low-energy excitations of interacting electrons in
solid are often described as quasiparticles.
• Quasiparticles can obey the same physical law as
fundamental particles, e.g., quasiparticle in graphene
is 2D massless Dirac fermion.
Graphene
Graphene band structure:
2D massless Dirac fermion
H. Ding
Dirac Semimetal with Band Inversion
as “singularity point”
of various topological
states
Normal
OR
Topological
Insulator
“3d graphene"
mass term
+
4-fold
Breaking
inversion
symmetry
Theory:
Na3Bi & Cd3As2
ARPES:
Z.K. Liu et al., Science 343, 864 (2014)
-
Noncentrosymmetri
c nonmagnetic Weyl
Semimetal
+
Z. Wang et al., PRB 85, 195320 (2012)
Z. Wang et al., PRB 88, 125427 (2013)
2-fold
Breaking
time reversal
symmetry
-
Magnetic Weyl
Semimetal
S. Borisenko et al., PRL 113, 027603 (2014)
S.Y. Xu et al., Science 347, 294 (2015)
H. Ding
A proposed simple Weyl semimetal: TaAs
Breaking inversion symmetry
Nonmagnetic materials - easy to grow and measure with ARPES
TaAs : 12 pairs of
Weyl nodes in the
bulk (8 W1, 4 W2)
W1 W2
H.M. Weng et al., Phys. Rev. X 5, 011029 (2015)
S. M. Huang et al., Nature Comm. (2015)
H. Ding
Properties of WSM
Exotic properties
Fermi arcs
Chiral anomaly
Negative magnetoresistance
“magnetic monopole”
Nonlocal transport
Quantum anomalous Hall effect
Unconventional superconductivity
……
H. Ding
30 years ago, when TWAS was established
the developing countries with 80% of world
population were producing 5% of world scientific
publications. R&D budget in developing countries-0.25% of GNP, while 2.5% in developed countries.
In real money,2 vs 100 billion USD.
In 2010 (according to UNESCO Report), scientific
output from 7 developing countries-Argentina
Brazil, China, India, Iran, Mexico and Turkey32%, with 10.6% from China alone (3%, 10 years
back), being second worldwide, after USA only.
Most importantly, quality not the number counts
first
Nature Index （2012-2014）
Factors contributing to success:
Sustainable government support:10-15 %
annual growth rate in last 10 years
Training and backflow of manpower: quite
good coverage of key branches
Investments in big facilities and instrumentation: Synchrotron, neutron, TEM,
STM, optics, etc
Consolidation of community: Forum on
High Temperature superconductivity:
13 sessions
Professor Salam’s dream
partly comes true
“We all look forward to a second revolution
in the Condensed Matter activity in developing countries with your appointment and
influence.”
The ICTP-Asia Pacific in Beijing, China
 Prof. Bai Chunli has submitted a
proposal of the Government of China
to establish the International Centre
for Theoretical Physics-Asia Pacific
(ICTP-AP) at the University of the
Chinese Academy of Sciences (UCAS)
as a category 2 Center at the auspices
of UNESCO
This proposal has been approved by
the UNESCO Executive Board at the
197th session on 15 October, 2015
 It will follow the model of ICTP
in Trieste, and will be contructed
at the UCAS campus in Huairou,
north of Beijing
UNESCO Secretary General
Irina Bokova’s letter to CAS
President Bai Chunli
About 50 Km from
Beijing Center
Thank you all!