Spin-Charge Separation.

Spin-Charge Separation. In condensed matter physics, the spin-charge separation is an unusual behavior of electrons in some materials under some special conditions that allows the electrons to behave as abound state of two independent particles, the spinon and the chargon, also known as the holon. The spinon only carries the spin of the electron but not the charge while the chargon/holon has spin equal to zero but its electric charge equals to the charge of the electron. Spin–charge separation is one of the most unusual manifestations of the concept of quasiparticles. This is really surprising because the "bare" quasiparticles are electrons, holes, phonons and photons, and all of them have the property that bosons are evenly charged and fermions are oddly charged and naively, one would think that any quasiparticle formed from these particles would also satisfy this property. Since the original electrons in the system are fermions, one of spinon and chargon has to be fermion, and the other one has to be boson. However, it is arbitrary to choose which either one to be fermionic. The formalism with bosonic chargon and fermionic spinion is usually refereed to as ""slave-fermion"" formalism, while the formalism with fermionic chargon and bosonic spinon is called the ""Schwinger boson"" formalism. Both approaches have been used for strongly correlated systems, but neither has been proved to be completely successful. One difficulty of the spin-charge separation is that, spinon and chargon are not gauge invariant quantities, i.e. unphysical objects, there is no direct physical probes to observe them. Therefore more often than not one has to use thermal dynamical or macroscopic techniques to see their effects. This implies that which formalism we choose is irrelevant to real physics, so in principle both approaches should give us the same answer. The reason we obtain radically different answers from these two formalisms is probably because of the wrong mean field solution we choose, which means that we are dealing with the spin-charge separation in a wrong way.

Probing Spin-Charge Separation in a Tomonaga-Luttinger Liquid. Y. Jompol,^1,* C. J. B. Ford,¹ J. P. Griffiths,¹ I. Farrer,¹ G. A. C. Jones,¹ D. Anderson,¹ D. A. Ritchie,¹T. W. Silk,² A. J. Schofield. In a one-dimensional (1D) system of interacting electrons, excitations of spin and charge travel at different speeds, according to the theory of a Tomonaga-Luttinger liquid (TLL) at low energies.

However, the clear observation of this spin-charge separation is an ongoing challenge experimentally. We have fabricated an electrostatically gated 1D system in which we observe spin-charge separation and also the predicted power-law suppression of tunnelinginto the 1D system. The spin-charge separation persists even beyond the low-energy regime where the TLL approximation should hold. TLL effects should therefore also be important in similar, but shorter, electrostatically gated wires, where interaction effects are being studied extensively worldwide. Физики разделили электроны на две квазичастицы. Английские ученые зафиксировали явление разделения спина и заряда в сверхтонких проводниках.Группа ученых из Кембриджского и Бирмингемского университетов (оба — Великобритания) зафиксировала явление разделения спина и заряда в сверхтонких проводниках.Наблюдать этот эффект можно в квазиодномерных системах, в которых взаимодействие электронов друг с другом приобретает гораздо большее значение, чем в обычных металлах. Попавшие в такие «стесненные условия» электроны рассматривают как комбинацию двух квазичастиц — спинона, переносящего только спин, и холона, переносящего только заряд. Свои эксперименты авторы построили на базе модели жидкости Томонаги — Латтинжера, которая описывает взаимодействие электронов в одномерных проводниках — так называемых квантовых проволоках. Эти проволоки ученые располагали на минимальном расстоянии от поверхности металла, электроны с которой «перепрыгивали» на проводники за счет эффекта квантового туннелирования. Вся система была охлаждена до сверхнизких температур (около 0,1 К) и помещена во внешнее магнитное поле; изменяя параметры поля и наблюдая за тем, как реагируют на это туннелирующие электроны, исследователи получили экспериментальные свидетельства разделения. «Такого рода проводники широко используются для соединения квантовых точек, которые в будущем, возможно, станут основой квантовых компьютеров, — объясняет один из авторов работы Крис Форд (Chris Ford). — Кроме того, изучение свойств квантовых проволок неразрывно связано с теориями сверхпроводимости и электропроводности твердых тел».

«Когда специалисты научились контролировать свойства электрона, появились полупроводники, а с ними и дешевые компьютеры, “айподы” и много чего еще, — говорит другой участник исследования Энди Скофилд (Andy Schofield). — Еще неизвестно, получится ли у нас столь же легко управлять этими новыми частицами». Подготовлено по материалам Кембриджского университета.

And finally:

KKR eyes market blitz of up to six IPOs July 31 2009 23:31. Kohlberg Kravis Roberts, the world’s biggest buy-out group, is preparing up to six companies for initial public offerings worth billions of dollars, including Toys R Us, as it sells some of its most valuable groups back to the stock market. There have been virtually no IPOs in the past two years, but as the worst of the financial crisis recedes and stock markets start to rebound, investors are eagerly waiting to see if private equity firms such as KKR will start listing companies bought in the boom years. A person familiar with KKR said the companies it was preparing to float included US toy retailer Toys R Us; HCA, one of America’s biggest hospital groups; First Data, the credit card processor; TDC, the Danish telecoms group; and Dollar General, the discount retailer. “We think there are five to six companies in the [KKR] portfolio that can be taken public in the next 12 months,” said a person familiar with KKR’s plans. The New York-based group has already filed for an IPO of Avago Technologies, the Singapore-based semiconductor company formerly known as Agilent, which it bought with Silver Lake for $2.66bn in 2005. The new IPOs would be a boost for KKR, which was founded by cousins Henry Kravis and George Roberts in 1976 and shot to fame 20 years ago with the $30bn takeover of RJR Nabisco, immortalised in the book Barbarians at the Gate. HCA was one of the biggest ever buy-outs when KKR, Bain Capital and Merrill Lynch paid $33bn for it in 2007. It runs 163 hospitals and 112 outpatient centres, generating $28.4bn of revenues last year. KKR in March valued its stake at $1.1bn. As HCA still has $26bn of debt, KKR is considering selling new shares to repay loans, rather than cashing out itself. It may do something similar with First Data, which it bought for $26bn in 2007 and has held up well in the recession, increasing adjusted earnings by 5 per cent last year.

The listings will be welcome news in an industry that has suffered two poor years because of falling stock markets and the crisis-hit banking sector. KKR underlined the woes of the buy-out sector by reporting a $1.2bn loss last year.

Willy and St.-Petersburg nayobki:

Former water polo star Mike Hale wanted by police over missing savings August 1, 2009

As the dashing captain of the Great Britain water polo team, Mike Hale was one of the best-known and respected players of his generation. But he is now being hunted by police after hundreds of investors accused him of disappearing with their life savings. Mr Hale, 60, vanished two weeks ago from his luxurious home in South Africa, where he ran an apparently successful asset management company that was popular with British expatriates. At least 20 million rand (£1.55 million) has been reported missing from the accounts at MJCM Insurance Brokers, including the savings of his wife and brother-in-law.