Tag Archives: Wolfgang Pauli

Proposed nanodevice made possible by particle that is its own antiparticle (Majorana particle)

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I’m not sure how much the mystery of Ettore Majorana’s disappearance in 1938 has to do with the latest research from Brazil on Majorana particles but it’s definitely fascinating,. From an April 6, 2018 news item on ScienceDaily,

In March 1938, the young Italian physicist Ettore Majorana disappeared mysteriously, leaving his country’s scientific community shaken. The episode remains unexplained, despite Leonardo Scascia’s attempt to unravel the enigma in his book The Disappearance of Majorana (1975).

Majorana, whom Enrico Fermi called a genius of Isaac Newton’s stature, vanished a year after making his main contribution to science. In 1937, when he was only 30, Majorana hypothesized a particle that is its own anti-particle and suggested that it might be the neutrino, whose existence had recently been predicted by Fermi and Wolfgang Pauli.

Eight decades later, Majorana fermions, or simply majoranas, are among the objects most studied by physicists. In addition to neutrinos — whose nature, whether or not they are majoranas, is one of the investigative goals of the mega-experiment Dune — another class not of fundamental particles but of quasi-particles or apparent particles has been investigated in the field of condensed matter. These Majorana quasi-particles can emerge as excitations in topological superconductors.

An April 6, 2018 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) press release on EurekAlert, which originated the news item,  reveals more about the Brazilian research (Note: Links have been removed),

A new study by PhD student Luciano Henrique Siliano Ricco with a scholarship from the São Paulo Research Foundation – FAPESP, in collaboration with his supervisor Antonio Carlos Ferreira Seridonio and others, was conducted on the Ilha Solteira campus of São Paulo State University (UNESP) in Brazil and described in an article in Scientific Reports.

“We propose a theoretical device that acts as a thermoelectric tuner – a tuner of heat and charge – assisted by Majorana fermions,” Seridonio said.

The device consists of a quantum dot (QD), represented in the Figure A by the symbol ε1. QDs are often called “artificial atoms.” In this case, the QD is located between two metallic leads at different temperatures.

The temperature difference is fundamental to allowing thermal energy to flow across the QD. A quasi-one-dimensional superconducting wire – called a Kitaev wire after its proponent, Russian physicist Alexei Kitaev, currently a professor at the California Institute of Technology (Caltech) in the US – is connected to the QD.

In this study, the Kitaev wire was ring- or U-shaped and had two majoranas (η1 and η2) at its edges. The majoranas emerge as excitations characterized by zero-energy modes.

“When the QD is coupled to only one side of the wire, the system behaves resonantly with regard to electrical and thermal conductance. In other words, it behaves like a thermoelectric filter,” said the principal investigator for the FAPESP fellowship.

“I should stress that this behavior as a filter for thermal and electrical energy occurs when the two majoranas ‘see’ each other via the wire, but only one of them ‘sees’ the QD in the connection.”

Another possibility investigated by the researchers involved making the QD “see” the two majoranas at the same time by connecting it to both ends of the Kitaev wire.

“By making the QD ‘see’ more of η1 or η2, i.e., by varying the system’s asymmetry, we can use the artificial atom as a tuner, where the thermal or electrical energy that flows through it is redshifted or blueshifted,” Seridonio said (see Figure B for illustrative explanation).

This theoretical paper, he added, is expected to contribute to the development of thermoelectric devices based on Majorana fermions.

Here’s a link to and a citation for the paper,

Tuning of heat and charge transport by Majorana fermions by L. S. Ricco, F. A. Dessotti, I. A. Shelykh, M. S. Figueira & A. C. Seridonio. Scientific Reportsvolume 8, Article number: 2790 (2018) doi:10.1038/s41598-018-21180-9 Published online: 12 February 2018

This paper is open access.

As I prepared to publish this piece I stumbled across a sad Sept. 3, 2018 article about Brazil and its overnight loss of heritage in a fire by Henry Grabar for slate.com (Note: Links have been removed),

On Sunday night, a fire ripped through Brazil’s National Museum in Rio de Janeiro, destroying the country’s most valuable storehouse of natural and anthropological history within hours.

Most of the 20 million items housed inside—including the skull of Luzia, the oldest human remains ever found in the Americas; one of the world’s largest archives of South America’s indigenous cultures; more than 26,000 fossils, 55,000 stuffed birds, and 5 million insect specimens; and a library of more than 500,000 books—are thought to have been destroyed.

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The loss is a symptom of a larger problem as Grabar notes in his article.

R.I.P. Heinrich Rohrer, co-inventor of the scanning tunneling microscope, 1933-2013

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Heinrich Rohrer died May 16, 2013 according to the May 22, 2013 news item on Nanowerk,

The co-inventor of the scanning tunneling microscope, Dr. Heinrich Rohrer, passed away on the evening of May 16, 2013. He was 79.

Heinrich Rohrer, IBM Fellow and Nobel Laureate, joined the IBM Research Laboratory in Zurich, Switzerland, in December of 1963, where he worked for 34 years.

After hiring a young scientist named Gerd Binnig in the late 1970s, the two started collaborating, brought closely together by their backgrounds in superconductivity and their fascination with atomic surfaces. The two scientists grew increasingly frustrated by the limits of the tools then available to study the distinct characteristics of atomic surfaces, so they decided to build their own, something that would be capable of seeing and manipulating atoms at the nanoscale level.

The May 2013 obituary on the IBM research website, which originated the news item, commemorates Rohrer’s Nobel winning accomplishment, the co-invention of the scanning tunneling microscope (STM),

Dr. Heinrich Rohrer, IBM Fellow, Nobel Laureate and co-inventor of the scanning tunneling microscope, passed away on the evening of May 16, 2013. He was 79. Dr. Rohrer joined IBM Research – Zurich in December of 1963, where he worked for 34 years.

“The invention of the scanning tunneling microscope was a seminal moment in the history of science and information technology,” said Dr. John E. Kelly III, IBM senior vice president and director of Research. “This invention gave scientists the ability to image, measure and manipulate atoms for the first time, and opened new avenues for information technology that we are still pursuing today.”

After hiring a young scientist named Gerd Binnig in the late 1970s, the two started collaborating, brought together by their backgrounds in superconductivity and their fascination with atomic surfaces. They grew increasingly frustrated by the limits of the tools then available, so they built their own, capable of seeing and manipulating atoms at the nanoscale level.

They began experimenting with tunneling, a quantum phenomenon in which electrons can escape the surface of a solid. When another surface approaches, the electron clouds can overlap and an electric current can flow.

Binnig and Rohrer found that when maneuvering a sharp metal conducting tip over the surface of a sample, the amount of electrical current flowing between the tip and the surface could be measured. Variations in the current provided information about the inner structure, and from this information,  they could build a three-dimensional atomic-scale map of the sample’s surface.

In January 1979, Binnig and Rohrer submitted their first patent disclosure on the scanning tunneling microscope (STM). Soon afterwards, with the help of fellow IBM researcher Christoph Gerber, they began to design and construct the microscope.

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In awarding Binnig and Rohrer the Nobel Prize in Physics in 1986, just five years after the first STM had been built, the Nobel committee said the invention opened up “entirely new fields… for the study of the structure of matter.”

In 2011, in the presence of 600 guests from throughout the research community, IBM and ETH Zurich dedicated the Binnig and Rohrer Nanotechnology Center in Rüschlikon in honor of the scientists’ achievements.

“ For me, Heini was father figure, role model, emotional and spiritual teacher, and best friend – all rolled into one. An eminent person, with an incredible sense of humanity and kindness. ”

-Gerd Binnig

Heinrich Rohrer was as famous for his kindly personality as for his sharp wit and humor. During the opening ceremony of the Center he participated in a public discussion with Binnig and Dr. Ralph Eicher, then president of ETH Zurich. After Binnig attempted to explain their invention, Rohrer jokingly apologized to the audience saying, “If you didn’t quite understand what Gerd just told you, you are not alone.”

Here are a few biographical details from the obituary page on the IBM website,

Heinrich Rohrer was born on June 6, 1933, in Buchs, Switzerland. In 1949, the Rohrer family moved to Zurich and a few years later Heinrich enrolled at the Swiss Federal Institute of Technology in Zurich (ETH), where he studied Physics under Wolfgang Pauli.

In the summer of 1961, Heinrich married Rose-Marie Egger and their honeymoon in the United States led to a two-year project studying thermal conductivity of type-II superconductors and metals at Rutgers University. Shortly thereafter in 1963, he returned to Switzerland to join the Physics department at the newly founded IBM Research – Zurich Laboratory.

The rest, as they say, is history.

ETA May 23, 2013: Dexter Johnson wrote a touching tribute in his May 23, 2013 posting, Heinrich Rohrer: The Modest Pioneer of Nanotechnology.